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serial_core: add pci uart early console support

PATCH Superseded Bin Gao 2 participants 2 messages May 15, 2015 TTY layer and serial drivers

v2 of 6 Superseded Latest is v6 →

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Bin Gao

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PATCH v2 1/2 serial_core: add pci uart early console support

On some Intel Atom SoCs, the legacy IO port UART(0x3F8) is not available. Instead, a 8250 compatible PCI uart can be used as early console. This patch adds pci support to the 8250 early console driver uart8250. For example, to enable pci uart(00:21.3) as early console on these platforms, append the following line to the kernel command line (assume baud rate is 115200):
earlyprintk=uart8250,pci32,0:24.2,115200n8

Signed-off-by Bin Gao <[email protected]>
---
 drivers/tty/serial/earlycon.c    |   6 ++
 drivers/tty/serial/serial_core.c | 140 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 144 insertions(+), 2 deletions(-)
drivers/tty/serial/earlycon.c +6 -0
index 5fdc9f3..586d84b 100644
@@ -196,7 +196,13 @@ static int __init param_setup_earlycon(char *buf)
 	}
 	return err;
 }
+
+/* x86 uses "earlyprintk=xxx", so we keep the compatibility here */
+#ifdef CONFIG_X86
+early_param("earlyprintk", param_setup_earlycon);
+#else
 early_param("earlycon", param_setup_earlycon);
+#endif
 
 int __init of_setup_earlycon(unsigned long addr,
 			     int (*setup)(struct earlycon_device *, const char *))
drivers/tty/serial/serial_core.c +138 -2

181 lines not on this page · raw message

Signature · 1 line
1.9.1
#1 lore raw

drivers/tty/serial/earlycon.c static int __init param_setup_earlycon(char *buf) · line 205

Quoted 6 lines
drivers/tty/serial/earlycon.c +5 -0
+/* x86 uses "earlyprintk=xxx", so we keep the compatibility here */
+#ifdef CONFIG_X86
+early_param("earlyprintk", param_setup_earlycon);
+#else
 early_param("earlycon", param_setup_earlycon);
+#endif

Is there any reason for not just allowing both ? That way you don't need an ifdef and the same command line (either) works everywhere ?

Quoted 10 lines

int __init of_setup_earlycon(unsigned long addr,

drivers/tty/serial/earlycon.c +0 -0
 			     int (*setup)(struct earlycon_device *, const char *))
drivers/tty/serial/serial_core.c +0 -0
index 0b7bb12..221143c 100644
@@ -34,10 +34,16 @@
 #include <linux/serial_core.h>
 #include <linux/delay.h>

drivers/tty/serial/serial_core.c line 45

Quoted 10 lines
drivers/tty/serial/serial_core.c +5 -0
 #include <linux/mutex.h>
+#include <linux/pci_regs.h>
 
 #include <asm/irq.h>
 #include <asm/uaccess.h>
 
+/* Only x86 has early pci access APIs */
+#if defined(CONFIG_PCI) && defined(CONFIG_X86)
+#include <asm/pci-direct.h>
+#endif

We should probably make that a define or Kconfig value so that any other port wanting early PCI console can add the needed direct functions without the defines here getting longer and longer

It would then be a single

#if defined(CONFIG_EARLY_PCI)

that could be put anywhere

Quoted 3 lines
drivers/tty/serial/serial_core.c +3 -0
+static int parse_pci_options(char *options, unsigned long *phys)
+{
+	u8 bus, dev, func;

...

drivers/tty/serial/serial_core.c uart_get_console(struct uart_port *ports, int nr, struct console *co) · line 1906

Quoted 4 lines
drivers/tty/serial/serial_core.c +4 -0
+failed:
+	pr_err("Invalid earlycon pci parameters\n");
+	return -EINVAL;
+}

#else
static int parse_pci_options(char *options, unsigned long *phys)

{
	pr_err("earlycon pci not available\n");
	return -EINVAL;
}

drivers/tty/serial/serial_core.c

Quoted 2 lines
drivers/tty/serial/serial_core.c +2 -0
+#endif
+

The all the ifdef mess below goes away

Alan