serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers
PATCH v5 1/1 serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers
Add tunable RX interrupt trigger I/F of FIFO buffers.
Serial devices are used as not only message communication devices but control or sending communication devices. For the latter uses, normally small data will be exchanged, so user applications want to receive data unit as soon as possible for real-time tendency. If we have a sensor which sends a 1 byte data each time and must control a device based on the sensor feedback, the RX interrupt should be triggered for each data.
According to HW specification of serial UART devices, RX interrupt trigger can be changed, but the trigger is hard-coded. For example, RX interrupt trigger in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets the trigger to only 8bytes.
This patch makes some devices change RX interrupt trigger from userland.
<How to use>
- Read current setting
# cat /sys/dev/char/4\:64/rx_int_trig 8
- Write user setting
# echo 1 > /sys/dev/char/4\:64/rx_int_trig # cat /sys/dev/char/4\:64/rx_int_trig 1
<Support uart devices>
- 16550A and Tegra (1, 4, 8, or 14 bytes)
- 16650V2 (8, 16, 24, or 28 bytes)
- 16654 (8, 16, 56, or 60 bytes)
- 16750 (1, 16, 32, or 56 bytes)
Changed in V2:
- Use _IOW for TIOCSFIFORTRIG definition
- Pass the interrupt trigger value itself
Changes in V3:
- Change I/F from ioctl(2) to sysfs(rx_int_trig)
Changes in V4:
- Introduce fifo_bug flag in uart_8250_port structure
This is enabled only when parity is enabled and UART_BUG_PARITY is enabled for up->bugs. If this flag is enabled, user cannot set RX trigger.
- Return -EOPNOTSUPP when it does not support device at convert_fcr2val() and at convert_val2rxtrig()
- Set the nearest lower RX trigger when users input a meaningless value at convert_val2rxtrig()
- Check whether p->fcr is existing at serial8250_clear_and_reinit_fifos()
- Set fcr = up->fcr in the begging of serial8250_do_set_termios()
Changes in V5:
- Support Tegra, 16650V2, 16654, and 16750
- Store default FCR value to up->fcr when the port is first created
- Add rx_trig_byte[] in uart_config[] for each device and use rx_trig_byte[] in convert_fcr2val() and convert_val2rxtrig()
--- drivers/tty/serial/8250/8250.h | 7 + drivers/tty/serial/8250/8250_core.c | 184 ++++++++++++++++++++++++++++++++--- drivers/tty/serial/serial_core.c | 18 ++- include/linux/serial_8250.h | 2 include/linux/serial_core.h | 4 + 5 files changed, 193 insertions(+), 22 deletions(-)
drivers/tty/serial/8250/8250.h +7 -0
@@ -12,6 +12,7 @@*/ #include <linux/serial_8250.h> +#include <linux/serial_reg.h> #include <linux/dmaengine.h> struct uart_8250_dma {
@@ -55,11 +56,17 @@ struct old_serial_port {unsigned long irqflags; }; +#define FCR_RX_TRIG_OFFSET 6 +#define FCR_RX_TRIG_BITS (x) (((x) >> FCR_RX_TRIG_OFFSET) & 0x3) +#define FCR_RX_TRIG_MAX_STATE \ +((FCR_RX_TRIG_BITS(UART_FCR_R_TRIG_11))-(FCR_RX_TRIG_BITS(UART_FCR_R_TRIG_00))) +struct serial8250_config {const char *name;unsigned short fifo_size;unsigned short tx_loadsz;unsigned char fcr; +unsigned char rx_trig_byte[FCR_RX_TRIG_MAX_STATE ];unsigned int flags; };
drivers/tty/serial/8250/8250_core.c +169 -15
271 lines not on this page · raw message
drivers/tty/serial/serial_core.c +11 -7
@@ -2548,15 +2548,16 @@ static struct attribute *tty_dev_attrs[] = { NULL, }; -static const struct attribute_group tty_dev_attr_group = { +static struct attribute_group tty_dev_attr_group = { .attrs = tty_dev_attrs, }; -static const struct attribute_group *tty_dev_attr_groups[] = { - &tty_dev_attr_group, -NULL - }; - +static void make_uport_attr_grps (struct uart_port *uport) +{ + uport->attr_grps[0 ] = &tty_dev_attr_group; +if (uport->dev_spec_attr_group) + uport->attr_grps[1 ] = uport->dev_spec_attr_group; +}/** * uart_add_one_port - attach a driver-defined port structure
@@ -2607,12 +2608,15 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)uart_configure_port (drv, state, uport); +make_uport_attr_grps (uport); +/* * Register the port whether it's detected or not. This allows * setserial to be used to alter this port's parameters. */ tty_dev =tty_port_register_device_attr (port, drv->tty_driver, - uport->line, uport->dev, port, tty_dev_attr_groups); + uport->line, uport->dev, port, + (const struct attribute_group **)uport->attr_grps);if (likely (!IS_ERR (tty_dev))) {device_set_wakeup_capable (tty_dev,1 ); }else {
include/linux/serial_8250.h +2 -0
@@ -74,8 +74,10 @@ struct uart_8250_port {struct list_head list;/* ports on this IRQ */ unsigned short capabilities;/* port capabilities */ unsigned short bugs;/* port bugs */ +bool fifo_bug;/* min RX trigger if enabled */ unsigned int tx_loadsz;/* transmit fifo load size */ unsigned char acr; +unsigned char fcr;unsigned char ier;unsigned char lcr;unsigned char mcr;
include/linux/serial_core.h +4 -0
@@ -113,6 +113,8 @@ struct uart_icount { typedef unsigned int __bitwise__ upf_t; +#define MAX_ATTR_GRPS 3 +struct uart_port {spinlock_t lock;/* port lock */ unsigned long iobase; /* in/out[bwl] */
@@ -195,6 +197,8 @@ struct uart_port {unsigned int line;/* port index */ resource_size_t mapbase;/* for ioremap */ struct device *dev;/* parent device */ +struct attribute_group *dev_spec_attr_group;/* specific attribute */ +struct attribute_group *attr_grps[MAX_ATTR_GRPS ];/* all attr. groups */ unsigned char hub6;/* this should be in the 8250 driver */ unsigned char suspended;unsigned char irq_wake;
PATCH 1/1 serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers
/* I found a bug in V5, so I resend this as V5.1. Please do not review V5. */
Add tunable RX interrupt trigger I/F of FIFO buffers.
Serial devices are used as not only message communication devices but control or sending communication devices. For the latter uses, normally small data will be exchanged, so user applications want to receive data unit as soon as possible for real-time tendency. If we have a sensor which sends a 1 byte data each time and must control a device based on the sensor feedback, the RX interrupt should be triggered for each data.
According to HW specification of serial UART devices, RX interrupt trigger can be changed, but the trigger is hard-coded. For example, RX interrupt trigger in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets the trigger to only 8bytes.
This patch makes some devices change RX interrupt trigger from userland.
<How to use>
- Read current setting
# cat /sys/dev/char/4\:64/rx_int_trig 8
- Write user setting
# echo 1 > /sys/dev/char/4\:64/rx_int_trig # cat /sys/dev/char/4\:64/rx_int_trig 1
<Support uart devices>
- 16550A and Tegra (1, 4, 8, or 14 bytes)
- 16650V2 (8, 16, 24, or 28 bytes)
- 16654 (8, 16, 56, or 60 bytes)
- 16750 (1, 16, 32, or 56 bytes)
Changed in V2:
- Use _IOW for TIOCSFIFORTRIG definition
- Pass the interrupt trigger value itself
Changes in V3:
- Change I/F from ioctl(2) to sysfs(rx_int_trig)
Changes in V4:
- Introduce fifo_bug flag in uart_8250_port structure
This is enabled only when parity is enabled and UART_BUG_PARITY is enabled for up->bugs. If this flag is enabled, user cannot set RX trigger.
- Return -EOPNOTSUPP when it does not support device at convert_fcr2val() and at convert_val2rxtrig()
- Set the nearest lower RX trigger when users input a meaningless value at convert_val2rxtrig()
- Check whether p->fcr is existing at serial8250_clear_and_reinit_fifos()
- Set fcr = up->fcr in the begging of serial8250_do_set_termios()
Changes in V5:
- Support Tegra, 16650V2, 16654, and 16750
- Store default FCR value to up->fcr when the port is first created
- Add rx_trig_byte[] in uart_config[] for each device and use rx_trig_byte[] in convert_fcr2val() and convert_val2rxtrig()
Changes in V5.1:
- Fix FCR_RX_TRIG_MAX_STATE definition
--- drivers/tty/serial/8250/8250.h | 6 + drivers/tty/serial/8250/8250_core.c | 184 ++++++++++++++++++++++++++++++++--- drivers/tty/serial/serial_core.c | 18 ++- include/linux/serial_8250.h | 2 include/linux/serial_core.h | 4 + 5 files changed, 192 insertions(+), 22 deletions(-)
drivers/tty/serial/8250/8250.h +6 -0
@@ -12,6 +12,7 @@*/ #include <linux/serial_8250.h> +#include <linux/serial_reg.h> #include <linux/dmaengine.h> struct uart_8250_dma {
@@ -55,11 +56,16 @@ struct old_serial_port {unsigned long irqflags; }; +#define FCR_RX_TRIG_OFFSET 6 +#define FCR_RX_TRIG_BITS (x) (((x) >> FCR_RX_TRIG_OFFSET) & 0x3) +#define FCR_RX_TRIG_MAX_STATE 4 +struct serial8250_config {const char *name;unsigned short fifo_size;unsigned short tx_loadsz;unsigned char fcr; +unsigned char rx_trig_byte[FCR_RX_TRIG_MAX_STATE ];unsigned int flags; };
drivers/tty/serial/8250/8250_core.c +169 -15
271 lines not on this page · raw message
drivers/tty/serial/serial_core.c +11 -7
@@ -2548,15 +2548,16 @@ static struct attribute *tty_dev_attrs[] = { NULL, }; -static const struct attribute_group tty_dev_attr_group = { +static struct attribute_group tty_dev_attr_group = { .attrs = tty_dev_attrs, }; -static const struct attribute_group *tty_dev_attr_groups[] = { - &tty_dev_attr_group, -NULL - }; - +static void make_uport_attr_grps (struct uart_port *uport) +{ + uport->attr_grps[0 ] = &tty_dev_attr_group; +if (uport->dev_spec_attr_group) + uport->attr_grps[1 ] = uport->dev_spec_attr_group; +}/** * uart_add_one_port - attach a driver-defined port structure
@@ -2607,12 +2608,15 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)uart_configure_port (drv, state, uport); +make_uport_attr_grps (uport); +/* * Register the port whether it's detected or not. This allows * setserial to be used to alter this port's parameters. */ tty_dev =tty_port_register_device_attr (port, drv->tty_driver, - uport->line, uport->dev, port, tty_dev_attr_groups); + uport->line, uport->dev, port, + (const struct attribute_group **)uport->attr_grps);if (likely (!IS_ERR (tty_dev))) {device_set_wakeup_capable (tty_dev,1 ); }else {
include/linux/serial_8250.h +2 -0
@@ -74,8 +74,10 @@ struct uart_8250_port {struct list_head list;/* ports on this IRQ */ unsigned short capabilities;/* port capabilities */ unsigned short bugs;/* port bugs */ +bool fifo_bug;/* min RX trigger if enabled */ unsigned int tx_loadsz;/* transmit fifo load size */ unsigned char acr; +unsigned char fcr;unsigned char ier;unsigned char lcr;unsigned char mcr;
include/linux/serial_core.h +4 -0
@@ -113,6 +113,8 @@ struct uart_icount { typedef unsigned int __bitwise__ upf_t; +#define MAX_ATTR_GRPS 3 +struct uart_port {spinlock_t lock;/* port lock */ unsigned long iobase; /* in/out[bwl] */
@@ -195,6 +197,8 @@ struct uart_port {unsigned int line;/* port index */ resource_size_t mapbase;/* for ioremap */ struct device *dev;/* parent device */ +struct attribute_group *dev_spec_attr_group;/* specific attribute */ +struct attribute_group *attr_grps[MAX_ATTR_GRPS ];/* all attr. groups */ unsigned char hub6;/* this should be in the 8250 driver */ unsigned char suspended;unsigned char irq_wake;
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2683
Quoted 10 lines
drivers/tty/serial/8250/8250_core.c +9
-0+static int convert_val2rxtrig (struct uart_8250_port *up,unsigned char val) +{ +const struct serial8250_config *conf_type = &uart_config[up->port.type]; +int i; + +if (!conf_type->rx_trig_byte[FCR_RX_TRIG_BITS (UART_FCR_R_TRIG_00 )]) { +pr_info ("Not support RX-trigger setting for this serial %s\n" , + conf_type->name); +return -EOPNOTSUPP ;
We don't want the pr_info here - otherwise users can flood the logs. The err code is sufficient.
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2689
Quoted 4 lines
drivers/tty/serial/8250/8250_core.c +4
-0+for (i =1 ; i <FCR_RX_TRIG_MAX_STATE ; i++) { +if (val < conf_type->rx_trig_byte[i]) +/* Use the nearest lower value */ +return (--i) <<FCR_RX_TRIG_OFFSET ;
Odd case here - your 16654 entry has a minimum of 8 so if I pass 1 then it'll return -1 ? I guess for that case the best we can do is to set 8.
Other trivial thing to tweak - you have "uaser" in spot instead of "user".
With those two fixed it looks good to me.
Alan
Hi Alan,
Thank you for your review.
Quoted 13 lines · One Thousand Gnomes
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2683
Quoted 10 lines
drivers/tty/serial/8250/8250_core.c +9
-0+static int convert_val2rxtrig (struct uart_8250_port *up,unsigned char val) +{ +const struct serial8250_config *conf_type = &uart_config[up->port.type]; +int i; + +if (!conf_type->rx_trig_byte[FCR_RX_TRIG_BITS (UART_FCR_R_TRIG_00 )]) { +pr_info ("Not support RX-trigger setting for this serial %s\n" , + conf_type->name); +return -EOPNOTSUPP ;We don't want the
pr_infohere - otherwise users can flood the logs. The err code is sufficient.
OK, I'll delete this pr_info().
Quoted 7 lines
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2689
Quoted 4 lines
drivers/tty/serial/8250/8250_core.c +4
-0+for (i =1 ; i <FCR_RX_TRIG_MAX_STATE ; i++) { +if (val < conf_type->rx_trig_byte[i]) +/* Use the nearest lower value */ +return (--i) <<FCR_RX_TRIG_OFFSET ;Odd case here - your 16654 entry has a minimum of 8 so if I pass 1 then it'll return -1 ? I guess for that case the best we can do is to set 8.
No, in that case, this function returns 0.
Note that the "i" starts from 1, so the minimal value is 0. Actually convert_val2rxtrig() returns the index of rx_trig_byte, and when val == 1, it returns 0 and caller gets rx_trig_byte[0] == 8.
Quoted 1 line
Other trivial thing to tweak - you have "uaser" in spot instead of "user".
Oops, I'll fix it.
Thanks,
Yoshihiro YUNOMAE
Quoted 9 lines
With those two fixed it looks good to me.
Alan
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Signature · 4 lines
Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected]
Quoted 16 lines · Yoshihiro YUNOMAE
/* I found a bug in V5, so I resend this as V5.1. Please do not review V5. */
Add tunable RX interrupt trigger I/F of FIFO buffers.
Serial devices are used as not only message communication devices but control or sending communication devices. For the latter uses, normally small data will be exchanged, so user applications want to receive data unit as soon as possible for real-time tendency. If we have a sensor which sends a 1 byte data each time and must control a device based on the sensor feedback, the RX interrupt should be triggered for each data.According to HW specification of serial UART devices, RX interrupt trigger can be changed, but the trigger is hard-coded. For example, RX interrupt trigger in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets the trigger to only 8bytes.
drivers/tty/serial/8250/8250.h struct old_serial_port { · line 59
Quoted 2 lines
drivers/tty/serial/8250/8250.h +1
-0+#define FCR_RX_TRIG_OFFSET 6
Isn't "SHIFT" the usual term rather than "OFFSET". Why not add this define into include/uapi/linux/serial_reg.h, along with all the other UART_FCR_TRIGGER_* defines?
Quoted 1 line
+#define
FCR_RX_TRIG_BITS(x)(((x) >>FCR_RX_TRIG_OFFSET) &0x3)
Perhaps use UART_FCR_TRIGGER_MASK rather than a hard-coded "3" (and then you'd have to mask before shifting).
Quoted 6 lines
drivers/tty/serial/8250/8250_core.c +0
-1@@ -2275,10 +2276,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,if (up->capabilities &UART_CAP_FIFO && port->fifosize >1 ) { - fcr = uart_config[port->type].fcr;
drivers/tty/serial/8250/8250_core.c serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, · line 2284
Quoted 10 lines
drivers/tty/serial/8250/8250_core.c +5
-3-if ((baud <2400 && !up->dma) || fifo_bug) { - fcr &= ~UART_FCR_TRIGGER_MASK ; - fcr |=UART_FCR_TRIGGER_1 ; +/* NOTE: If fifo_bug is not set, a uaser can set RX_trigger. */ +if ((baud <2400 && !up->dma && + (up->fcr == uart_config[port->type].fcr)) || up->fifo_bug) { + up->fcr &= ~UART_FCR_TRIGGER_MASK ; + up->fcr |=UART_FCR_TRIGGER_1 ; } }
Does the "(up->fcr == uart_config[port->type].fcr)" term prevent the user from changing the trigger level multiple times? Perhaps this is intended?
Quoted 1 line
+static int
convert_fcr2val(struct uart_8250_port *up)
"val" is rather generic here, and doesn't describe what the function is doing. What about fcr_get_rxtrig_bytes()?
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2670
Quoted 6 lines
drivers/tty/serial/8250/8250_core.c +6
-0+{ +const struct serial8250_config *conf_type = &uart_config[up->port.type]; +unsigned char rx_trig_raw = up->fcr &UART_FCR_TRIGGER_MASK ; +unsigned char val; + + val = conf_type->rx_trig_byte[FCR_RX_TRIG_BITS (rx_trig_raw)];
Given that FCR_RX_TRIG_BITS() does all the required shifting/masking, why not just:
val = conf_type->rx_trig_byte[FCR_RX_TRIG_BITS(up->fcr)];
Quoted 1 line
+static int
convert_val2rxtrig(struct uart_8250_port *up, unsigned char val)
Perhaps name this bytes_to_fcr_txtrig()?
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2808
Quoted 8 lines
drivers/tty/serial/8250/8250_core.c +8
-0+static void register_dev_spec_attr_grp (struct uart_8250_port *up) +{ +switch (up->port.type) { +case PORT_16550A : +case PORT_16650V2 : +case PORT_16654 : +case PORT_16750 : +case PORT_TEGRA :
Why not replace that with:
const struct serial8250_config *conf_type = &uart_config[up->port.type]; if (conf_type->rx_trig_byte[0]) {
(or something like that anyway)
That means this switch statement doesn't need to be updated when new UART types are modified to set up the rx_trig_byte field.
Hi Stephen,
Thank you for your review.
Quoted 16 lines · Stephen Warren
Quoted 14 lines · Yoshihiro YUNOMAE
/* I found a bug in V5, so I resend this as V5.1. Please do not review V5. */
Add tunable RX interrupt trigger I/F of FIFO buffers.
Serial devices are used as not only message communication devices but control or sending communication devices. For the latter uses, normally small data will be exchanged, so user applications want to receive data unit as soon as possible for real-time tendency. If we have a sensor which sends a 1 byte data each time and must control a device based on the sensor feedback, the RX interrupt should be triggered for each data.According to HW specification of serial UART devices, RX interrupt trigger can be changed, but the trigger is hard-coded. For example, RX interrupt trigger in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets the trigger to only 8bytes.
Quoted 5 lines
drivers/tty/serial/8250/8250.h struct old_serial_port { · line 59
Quoted 3 lines
drivers/tty/serial/8250/8250.h +1
-0+#define FCR_RX_TRIG_OFFSET 6Isn't "SHIFT" the usual term rather than "OFFSET". Why not add this
OK, I'll rename this.
Quoted 2 lines
define into
include/uapi/linux/serial_reg.h, along with all the other UART_FCR_TRIGGER_* defines?
I thought these definition will not be used in userland. I'll move these in serial_reg.h.
Quoted 4 lines
Quoted 1 line
+#define
FCR_RX_TRIG_BITS(x)(((x) >>FCR_RX_TRIG_OFFSET) &0x3)Perhaps use
UART_FCR_TRIGGER_MASKrather than a hard-coded "3" (and then you'd have to mask before shifting).
OK, I'll define FCR_RX_TRIG_BITS as follows:
#define UART_FCR_R_TRIG_SHIFT 6
#define UART_FCR_R_TRIG_BITS(x) \
(((x) & UART_FCR_TRIGGER_MASK) >> UART_FCR_R_TRIG_SHIFT)Quoted 4 lines
Quoted 3 lines
drivers/tty/serial/8250/8250_core.c +0
-0@@ -2275,10 +2276,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
Quoted 16 lines
drivers/tty/serial/8250/8250_core.c serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, · line 2334
Quoted 12 lines
drivers/tty/serial/8250/8250_core.c +5
-4if (up->capabilities &UART_CAP_FIFO && port->fifosize >1 ) { - fcr = uart_config[port->type].fcr; -if ((baud <2400 && !up->dma) || fifo_bug) { - fcr &= ~UART_FCR_TRIGGER_MASK ; - fcr |=UART_FCR_TRIGGER_1 ; +/* NOTE: If fifo_bug is not set, a uaser can set RX_trigger. */ +if ((baud <2400 && !up->dma && + (up->fcr == uart_config[port->type].fcr)) || up->fifo_bug) { + up->fcr &= ~UART_FCR_TRIGGER_MASK ; + up->fcr |=UART_FCR_TRIGGER_1 ; } }Does the "(
up->fcr== uart_config[port->type].fcr)" term prevent the user from changing the trigger level multiple times? Perhaps this is intended?
No, this means that if a user changed FCR value before setting termios, use the changed value because the user think changed value is always set. But, I thought this is not straightforward and it cannot help when the user want to use default FCR value.
Could I add FCR changed flag(user_changed_fcr) in uart_8250_port structure and check the flag here?
Or shouldn't the driver check the user changing?
Quoted 4 lines
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2664
Quoted 1 line
drivers/tty/serial/8250/8250_core.c +1
-0+static int convert_fcr2val (struct uart_8250_port *up)"val" is rather generic here, and doesn't describe what the function is doing. What about
fcr_get_rxtrig_bytes()?
Sure.
Quoted 11 lines
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2670
Quoted 6 lines
drivers/tty/serial/8250/8250_core.c +6
-0+{ +const struct serial8250_config *conf_type = &uart_config[up->port.type]; +unsigned char rx_trig_raw = up->fcr &UART_FCR_TRIGGER_MASK ; +unsigned char val; + + val = conf_type->rx_trig_byte[FCR_RX_TRIG_BITS (rx_trig_raw)];Given that
FCR_RX_TRIG_BITS()does all the required shifting/masking, why not just:val = conf_type->rx_trig_byte[FCR_RX_TRIG_BITS(up->fcr)];
That's true. I'll fix it.
Quoted 3 lines
Quoted 1 line
+static int
convert_val2rxtrig(struct uart_8250_port *up, unsigned char val)Perhaps name this
bytes_to_fcr_txtrig()?
OK, I'll rename it to bytes_to_fcr_rxtrig().
Quoted 11 lines
drivers/tty/serial/8250/8250_core.c static int serial8250_request_port(struct uart_port *port) · line 2808
Quoted 8 lines
drivers/tty/serial/8250/8250_core.c +8
-0+static void register_dev_spec_attr_grp (struct uart_8250_port *up) +{ +switch (up->port.type) { +case PORT_16550A : +case PORT_16650V2 : +case PORT_16654 : +case PORT_16750 : +case PORT_TEGRA :Why not replace that with:
Quoted 7 lines
const struct
serial8250_config*conf_type= &uart_config[up->port.type]; if (conf_type->rx_trig_byte[0]) {(or something like that anyway)
That means this switch statement doesn't need to be updated when new UART types are modified to set up the
rx_trig_bytefield.
Nice idea! I'll use your idea.
Thanks,
Yoshihiro YUNOMAE
Signature · 4 lines
Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected]
Quoted 53 lines · Yoshihiro YUNOMAE
Hi Stephen,
Thank you for your review.
Quoted 44 lines · Stephen Warren
Quoted 32 lines · Yoshihiro YUNOMAE
/* I found a bug in V5, so I resend this as V5.1. Please do not review V5. */
Add tunable RX interrupt trigger I/F of FIFO buffers.
Serial devices are used as not only message communication devices but control
or sending communication devices. For the latter uses, normally small data
will be exchanged, so user applications want to receive data unit as soon as
possible for real-time tendency. If we have a sensor which sends a 1 byte data
each time and must control a device based on the sensor feedback, the RX interrupt should be triggered for each data.According to HW specification of serial UART devices, RX interrupt trigger
can be changed, but the trigger is hard-coded. For example, RX interrupt trigger
in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets
the trigger to only 8bytes.drivers/tty/serial/8250/8250_core.c +0
-2@@ -2275,10 +2276,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) { - fcr = uart_config[port->type].fcr; -if ((baud <2400 && !up->dma) || fifo_bug) {drivers/tty/serial/8250/8250_core.c serial8250_do_set_termios(struct uart_port · line 2334
Quoted 10 lines
drivers/tty/serial/8250/8250_core.c +5
-2- fcr &= ~UART_FCR_TRIGGER_MASK ; - fcr |=UART_FCR_TRIGGER_1 ; +/* NOTE: If fifo_bug is not set, a uaser can set RX_trigger. */ +if ((baud <2400 && !up->dma && + (up->fcr == uart_config[port->type].fcr)) || up->fifo_bug) { + up->fcr &= ~UART_FCR_TRIGGER_MASK ; + up->fcr |=UART_FCR_TRIGGER_1 ; } }Quoted 3 lines
Does the "(
up->fcr== uart_config[port->type].fcr)" term prevent the user from changing the trigger level multiple times? Perhaps this is intended?
Quoted 7 lines
No, this means that if a user changed FCR value before setting termios, use the changed value because the user think changed value is always set. But, I thought this is not straightforward and it cannot help when the user want to use default FCR value.
Could I add FCR changedflag(user_changed_fcr)inuart_8250_portstructure and check the flag here?
Or shouldn't the driver check the user changing?
Oh, I wasn't aware that the user could change FCR directly. To be honest, I'm not sure of the best way to resolve that kind of conflict...
Hi Stephen,
Thank you for your reply.
Quoted 33 lines · Stephen Warren
Quoted 24 lines · Yoshihiro YUNOMAE
Quoted 20 lines
Quoted 9 lines
drivers/tty/serial/8250/8250_core.c +0
-2@@ -2275,10 +2276,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) { - fcr = uart_config[port->type].fcr; -if ((baud <2400 && !up->dma) || fifo_bug) {drivers/tty/serial/8250/8250_core.c serial8250_do_set_termios(struct uart_port · line 2334
Quoted 10 lines
drivers/tty/serial/8250/8250_core.c +5
-2- fcr &= ~UART_FCR_TRIGGER_MASK ; - fcr |=UART_FCR_TRIGGER_1 ; +/* NOTE: If fifo_bug is not set, a uaser can set RX_trigger. */ +if ((baud <2400 && !up->dma && + (up->fcr == uart_config[port->type].fcr)) || up->fifo_bug) { + up->fcr &= ~UART_FCR_TRIGGER_MASK ; + up->fcr |=UART_FCR_TRIGGER_1 ; } }Quoted 3 lines
Does the "(
up->fcr== uart_config[port->type].fcr)" term prevent the user from changing the trigger level multiple times? Perhaps this is intended?Quoted 7 lines
No, this means that if a user changed FCR value before setting termios, use the changed value because the user think changed value is always set. But, I thought this is not straightforward and it cannot help when the user want to use default FCR value.
Could I add FCR changedflag(user_changed_fcr)inuart_8250_portstructure and check the flag here?
Or shouldn't the driver check the user changing?
Quoted 2 lines
Oh, I wasn't aware that the user could change FCR directly. To be honest, I'm not sure of the best way to resolve that kind of conflict...
OK. For simplicity, I don't implement the checking.
Even if FCR is changed here, users can change it any time, so this is not so big problem, I think.
Thanks,
Yoshihiro YUNOMAE
Signature · 4 lines
Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected]