Can one set GPIO direction in pinmux definition?
For a MX28 based hardware I am working with I need to use AUART4
I need to configure this AUART4 as uart only when necessary and at all other times pins associated with AUART4 need to be configured as inputs.
I am using following DT definitions to setup AUART4 mux but can't figure out how to setup pin direction via DT, can it be done or I need to do it in C code?
apb at 80000000 {
apbh at 80000000 {
auart4_pins_a: auart4 at 0 {
reg = <0>;
fsl,pinmux-ids = <
0x3142 /*
MX28_PAD_SAIF0_MCLK__AUART4_CTS */
0x3152 /*
MX28_PAD_SAIF0_LRCLK__AUART4_RTS */
0x3162 /*
MX28_PAD_SAIF0_BITCLK__AUART4_RX */
0x3172 /*
MX28_PAD_SAIF0_SDATA0__AUART4_TX */
>;
fsl,drive-strength = <0>;
fsl,voltage = <1>;
fsl,pull-up = <0>;
};
auart4_highz_pins: auart4-gpio at 0 {
reg = <0>;
fsl,pinmux-ids = <
0x3143 /*
MX28_PAD_SAIF0_MCLK__GPIO_3_20 */
0x3153 /*
MX28_PAD_SAIF0_LRCLK__GPIO_3_21 */
0x3163 /*
MX28_PAD_SAIF0_BITCLK__GPIO_3_22 */
0x3173 /*
MX28_PAD_SAIF0_SDATA0__GPIO_3_23 */
>;
fsl,drive-strength = <0>;
fsl,voltage = <1>;
fsl,pull-up = <0>;
};
};
};
apbx at 80040000 {
auart4: serial at 80072000 {
pinctrl-names = "default", "auart";
pinctrl-0 = <&auart4_highz_pins>;
pinctrl-1 = <&auart4_pins_a>;
status = "okay";
};
};Quoted 5 lines · Subodh Nijsure
For a MX28 based hardware I am working with I need to use AUART4
I need to configure this AUART4 as uart only when necessary and at all other times pins associated with AUART4 need to be configured as inputs.
Out of curiosity, why?
BTW, you didn't CC any of the IMX maintainers, so it's likely they won't see your question. I've CC'd LinusW, Shawn, and Dong.
Quoted 32 lines
I am using following DT definitions to setup AUART4 mux but can't figure out how to setup pin direction via DT, can it be done or I need to do it in C code?
apb at 80000000 { apbh at 80000000 { auart4_pins_a: auart4 at 0 { reg = <0>; fsl,pinmux-ids = < 0x3142 /* MX28_PAD_SAIF0_MCLK__AUART4_CTS */ 0x3152 /* MX28_PAD_SAIF0_LRCLK__AUART4_RTS */ 0x3162 /* MX28_PAD_SAIF0_BITCLK__AUART4_RX */ 0x3172 /* MX28_PAD_SAIF0_SDATA0__AUART4_TX */ >; fsl,drive-strength = <0>; fsl,voltage = <1>; fsl,pull-up = <0>; }; auart4_highz_pins: auart4-gpio at 0 { reg = <0>; fsl,pinmux-ids = < 0x3143 /* MX28_PAD_SAIF0_MCLK__GPIO_3_20 */ 0x3153 /* MX28_PAD_SAIF0_LRCLK__GPIO_3_21 */ 0x3163 /* MX28_PAD_SAIF0_BITCLK__GPIO_3_22 */ 0x3173 /*
Quoted 8 lines
MX28_PAD_SAIF0_SDATA0__GPIO_3_23*/>; fsl,drive-strength = <0>; fsl,voltage = <1>; fsl,pull-up = <0>; }; }; };
I don't know IMX HW, but where is highz controlled? On other SoCs I'm familiar with, when a pad is configured as a GPIO, the highz state is controlled by the GPIO module, so there's nothing pinmux can do about it. Even if the pinmux HW does control highz, gpio_direction_*() are still meant to communicate with the pinctrl driver to implement this, so overriding it through the pinctrl configuration seems like a bad thing.
So I think your UART driver would have to request the GPIOs, and set them as inputs. So, I guess your UART node below would need a property listing the GPIOs to do this to.
Quoted 8 lines
apbx at 80040000 {
auart4: serial at 80072000 {
pinctrl-names = "default", "auart";
pinctrl-0 = <&auart4_highz_pins>;
pinctrl-1 = <&auart4_pins_a>;
status = "okay";
};
};Quoted 6 lines · Stephen Warren
Quoted 4 lines · Subodh Nijsure
For a MX28 based hardware I am working with I need to use AUART4
I need to configure this AUART4 as uart only when necessary and at all other times pins associated with AUART4 need to be configured as inputs.
Out of curiosity, why?
Out hardware is connected to external equipment, electric meter via this UART.
This electricity meter can also be read externally by an optical reader. Since this is a shared bus, we can't be sitting on that bus with our interface configured as UART as it prevents optical reader from talking to the meter. There are ways we can tell is optical meter is connected, if we detect that its connected we configure these pins as input else configure them for UART functionality.
Quoted 2 lines
BTW, you didn't CC any of the IMX maintainers, so it's likely they won't see your question. I've CC'd LinusW, Shawn, and Dong.
thanks.
Quoted 47 lines
Quoted 32 lines
I am using following DT definitions to setup AUART4 mux but can't figure out how to setup pin direction via DT, can it be done or I need to do it in C code?
apb at 80000000 { apbh at 80000000 { auart4_pins_a: auart4 at 0 { reg = <0>; fsl,pinmux-ids = < 0x3142 /* MX28_PAD_SAIF0_MCLK__AUART4_CTS */ 0x3152 /* MX28_PAD_SAIF0_LRCLK__AUART4_RTS */ 0x3162 /* MX28_PAD_SAIF0_BITCLK__AUART4_RX */ 0x3172 /* MX28_PAD_SAIF0_SDATA0__AUART4_TX */ >; fsl,drive-strength = <0>; fsl,voltage = <1>; fsl,pull-up = <0>; }; auart4_highz_pins: auart4-gpio at 0 { reg = <0>; fsl,pinmux-ids = < 0x3143 /* MX28_PAD_SAIF0_MCLK__GPIO_3_20 */ 0x3153 /* MX28_PAD_SAIF0_LRCLK__GPIO_3_21 */ 0x3163 /* MX28_PAD_SAIF0_BITCLK__GPIO_3_22 */ 0x3173 /*Quoted 8 lines
MX28_PAD_SAIF0_SDATA0__GPIO_3_23*/>; fsl,drive-strength = <0>; fsl,voltage = <1>; fsl,pull-up = <0>; }; }; };I don't know IMX HW, but where is highz controlled? On other SoCs I'm familiar with, when a pad is configured as a GPIO, the highz state is controlled by the GPIO module, so there's nothing pinmux can do about it. Even if the pinmux HW does control highz, gpio_direction_*() are still meant to communicate with the pinctrl driver to implement this, so overriding it through the pinctrl configuration seems like a bad thing.
Quoted 3 lines
So I think your UART driver would have to request the GPIOs, and set them as inputs. So, I guess your UART node below would need a property listing the GPIOs to do this to.
Right now that is what I am doing in my code, requesting GPIOs in UART drivers and setting up the direction. I just wanted to make sure there wasn't way to setup pin direction using pinmux itself.
Quoted 9 lines
Quoted 9 lines
apbx at 80040000 { auart4: serial at 80072000 { pinctrl-names = "default", "auart"; pinctrl-0 = <&auart4_highz_pins>; pinctrl-1 = <&auart4_pins_a>; status = "okay"; }; };
Thanks.
-Subodh
Quoted 8 lines · Subodh Nijsure
Quoted 6 lines · Stephen Warren
Quoted 4 lines · Subodh Nijsure
For a MX28 based hardware I am working with I need to use AUART4
I need to configure this AUART4 as uart only when necessary and at all other times pins associated with AUART4 need to be configured as inputs.
Out of curiosity, why?
Quoted 8 lines
Our hardware is connected to external equipment, electric meter via this UART.
This electricity meter can also be read externally by an optical reader. Since this is a shared bus, we can't be sitting on that bus with our interface configured as UART as it prevents optical reader from talking to the meter. There are ways we can tell is optical meter is connected, if we detect that its connected we configure these pins as input else configure them for UART functionality.
OK, I guess it was something like that. Can the optical be plugged/unplugged at run-time, or is it a one-off thing? pinctrl would be appropriate for runtime. Maybe not so much for one-off detection at boot-time.
I wonder whether making the UART driver do the switching is the right thing though. I assume that:
* The UART driver can be used on systems (boards) that never have this HW configuration, and don't care about this at all.
* The detection of optical meter presence is entirely unrelated to the UART.
So probably, the muxing can be seen as completely external and unrelated to the UART HW module itself. Would it be better represented as a completely standalone and custom "RS232 bus mux" node/device instead of tacking this into the UART driver?
Quoted 47 lines · Subodh Nijsure
For a MX28 based hardware I am working with I need to use AUART4
I need to configure this AUART4 as uart only when necessary and at all other times pins associated with AUART4 need to be configured as inputs.
I am using following DT definitions to setup AUART4 mux but can't figure out how to setup pin direction via DT, can it be done or I need to do it in C code?
apb at 80000000 { apbh at 80000000 { auart4_pins_a: auart4 at 0 { reg = <0>; fsl,pinmux-ids = < 0x3142 /* MX28_PAD_SAIF0_MCLK__AUART4_CTS */ 0x3152 /* MX28_PAD_SAIF0_LRCLK__AUART4_RTS */ 0x3162 /* MX28_PAD_SAIF0_BITCLK__AUART4_RX */ 0x3172 /* MX28_PAD_SAIF0_SDATA0__AUART4_TX */ >; fsl,drive-strength = <0>; fsl,voltage = <1>; fsl,pull-up = <0>; }; auart4_highz_pins: auart4-gpio at 0 { reg = <0>; fsl,pinmux-ids = < 0x3143 /* MX28_PAD_SAIF0_MCLK__GPIO_3_20 */ 0x3153 /* MX28_PAD_SAIF0_LRCLK__GPIO_3_21 */ 0x3163 /* MX28_PAD_SAIF0_BITCLK__GPIO_3_22 */ 0x3173 /* MX28_PAD_SAIF0_SDATA0__GPIO_3_23 */ >; fsl,drive-strength = <0>; fsl,voltage = <1>; fsl,pull-up = <0>; }; }; };
Quoted 8 lines
apbx at 80040000 {
auart4: serial at 80072000 {
pinctrl-names = "default", "auart";
pinctrl-0 = <&auart4_highz_pins>;
pinctrl-1 = <&auart4_pins_a>;
status = "okay";
};
};Those pin definitions are defined per-device but they're parsed at module init - so you'd load uart, then your gpio stuff and your uart would stop working as it's input paths would have moved in the iomux controller. Until you unloaded the gpio and uart drivers, then loaded the right one. I am guessing you don't want to be forcibly loading and unloading drivers just to swap modes.
Someone did some kind of external bus muxing implementation ("extbus"?) a while back which could sort this out; it's since lost in time and space, or at least I can't figure out the terms I need to Google to recover it or how I saved my bookmark. You'd have to (re-)write the drivers to support the switch (i.e. dynamically parse pinctrl nodes for the swap or pass them by reference to the muxing implementation) and stop "working" while the other is in use, but I feel like I remember that only really supported the case where you had multiple potential plugin boards at boot (not hotpluggable).
In order to set the directions you'd need to define them in a driver-specific way, but IMO there needs to be a binding that configures gpio directions anyway since there's not one currently which is perplexing - for interrupt-capable GPIO sources it is implicit through the gpio interrupt domain, but for just inputs you can read, you have to rely on the bootloader setting it up and your driver knowing exactly what to do..
Signature · 2 lines
Matt Sealey <[email protected]> Product Development Analyst, Genesi USA, Inc.
Quoted 4 lines · Subodh Nijsure
Right now that is what I am doing in my code, requesting GPIOs in UART drivers and setting up the direction. I just wanted to make sure there wasn't way to setup pin direction using pinmux itself.
No, there is no way for pinctrl driver to set up gpio direction, which is completely gpio driver's job.
Signature · 2 lines
Regards, Shawn