[PATCH v1 1/1] x86/early_printk: Use 'mmio32' for consistency

[PATCH v1 1/1] x86/early_printk: Use 'mmio32' for consistency

[Andy Shevchenko]

First of all, using 'mmio' prevents proper implementation of 8-bit accessors.
Second, it's simply inconsistent with uart8250 set of options. Rename it to
'mmio32'. While at it, remove rather misleading comment in the documentation.
From now on mmio32 is self-explanatory and pciserial supports not only 32-bit
MMIO accessors.

Fixes: 3181424aeac2 ("x86/early_printk: Add support for MMIO-based UARTs")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 5 +----
 arch/x86/kernel/early_printk.c                  | 6 +++---
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 76e538c77e31..d9fd26b95b34 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1407,18 +1407,15 @@
 			earlyprintk=serial[,0x...[,baudrate]]
 			earlyprintk=ttySn[,baudrate]
 			earlyprintk=dbgp[debugController#]
+			earlyprintk=mmio32,membase[,{nocfg|baudrate}]
 			earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}]
 			earlyprintk=xdbc[xhciController#]
 			earlyprintk=bios
-			earlyprintk=mmio,membase[,{nocfg|baudrate}]
 
 			earlyprintk is useful when the kernel crashes before
 			the normal console is initialized. It is not enabled by
 			default because it has some cosmetic problems.
 
-			Only 32-bit memory addresses are supported for "mmio"
-			and "pciserial" devices.
-
 			Use "nocfg" to skip UART configuration, assume
 			BIOS/firmware has configured UART correctly.
 
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index b70e6e99fb17..dc053641698c 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -424,10 +424,10 @@ static int __init setup_early_printk(char *buf)
 	keep = (strstr(buf, "keep") != NULL);
 
 	while (*buf != '\0') {
-		if (!strncmp(buf, "mmio", 4)) {
-			early_mmio_serial_init(buf + 4);
+		if (!strncmp(buf, "mmio32", 6)) {
+			buf += 6;
+			early_mmio_serial_init(buf);
 			early_console_register(&early_serial_console, keep);
-			buf += 4;
 		}
 		if (!strncmp(buf, "serial", 6)) {
 			buf += 6;
-- 
2.47.2

Re: [PATCH v1 1/1] x86/early_printk: Use 'mmio32' for consistency

[dmkhn]

On Mon, Apr 07, 2025 at 08:22:14PM +0300, Andy Shevchenko wrote:
> First of all, using 'mmio' prevents proper implementation of 8-bit accessors.
> Second, it's simply inconsistent with uart8250 set of options. Rename it to
> 'mmio32'. While at it, remove rather misleading comment in the documentation.
> >From now on mmio32 is self-explanatory and pciserial supports not only 32-bit
> MMIO accessors.
> 
> Fixes: 3181424aeac2 ("x86/early_printk: Add support for MMIO-based UARTs")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Reviewed-by: Denis Mukhin <dmukhin@ford.com>

> ---
>  Documentation/admin-guide/kernel-parameters.txt | 5 +----
>  arch/x86/kernel/early_printk.c                  | 6 +++---
>  2 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 76e538c77e31..d9fd26b95b34 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1407,18 +1407,15 @@
>  			earlyprintk=serial[,0x...[,baudrate]]
>  			earlyprintk=ttySn[,baudrate]
>  			earlyprintk=dbgp[debugController#]
> +			earlyprintk=mmio32,membase[,{nocfg|baudrate}]
>  			earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}]
>  			earlyprintk=xdbc[xhciController#]
>  			earlyprintk=bios
> -			earlyprintk=mmio,membase[,{nocfg|baudrate}]
>  
>  			earlyprintk is useful when the kernel crashes before
>  			the normal console is initialized. It is not enabled by
>  			default because it has some cosmetic problems.
>  
> -			Only 32-bit memory addresses are supported for "mmio"
> -			and "pciserial" devices.
> -
>  			Use "nocfg" to skip UART configuration, assume
>  			BIOS/firmware has configured UART correctly.
>  
> diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
> index b70e6e99fb17..dc053641698c 100644
> --- a/arch/x86/kernel/early_printk.c
> +++ b/arch/x86/kernel/early_printk.c
> @@ -424,10 +424,10 @@ static int __init setup_early_printk(char *buf)
>  	keep = (strstr(buf, "keep") != NULL);
>  
>  	while (*buf != '\0') {
> -		if (!strncmp(buf, "mmio", 4)) {
> -			early_mmio_serial_init(buf + 4);
> +		if (!strncmp(buf, "mmio32", 6)) {
> +			buf += 6;
> +			early_mmio_serial_init(buf);
>  			early_console_register(&early_serial_console, keep);
> -			buf += 4;
>  		}
>  		if (!strncmp(buf, "serial", 6)) {
>  			buf += 6;
> -- 
> 2.47.2
> 

Re: [PATCH v1 1/1] x86/early_printk: Use 'mmio32' for consistency

[Ingo Molnar]

* Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> First of all, using 'mmio' prevents proper implementation of 8-bit accessors.
> Second, it's simply inconsistent with uart8250 set of options. Rename it to
> 'mmio32'. While at it, remove rather misleading comment in the documentation.
> From now on mmio32 is self-explanatory and pciserial supports not only 32-bit
> MMIO accessors.
> 
> Fixes: 3181424aeac2 ("x86/early_printk: Add support for MMIO-based UARTs")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 5 +----
>  arch/x86/kernel/early_printk.c                  | 6 +++---
>  2 files changed, 4 insertions(+), 7 deletions(-)

Thank you for taking care of this, I've queued these fixes in tip:x86/urgent.

	Ingo