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

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Message-ID: <20250407172214.792745-1-andriy.shevchenko@linux.intel.com>
Date: Mon,  7 Apr 2025 20:22:14 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1 1/1] x86/early_printk: Use 'mmio32' for consistency

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@...ux.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