linux-kernel - [PATCH 1/2] tty: serial: samsung: Fix A7-A11 serial earlycon SError

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Message-ID: <20240907111431.2970-2-towinchenmi@gmail.com>
Date: Sat,  7 Sep 2024 19:06:44 +0800
From: Nick Chan <towinchenmi@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Cc: asahi@...ts.linux.dev,
	Nick Chan <towinchenmi@...il.com>
Subject: [PATCH 1/2] tty: serial: samsung: Fix A7-A11 serial earlycon SError

Apple's earlier SoCs, like A7-A11, requires 32-bit writes for the serial
port. Otherwise, a SError happens when writing to UTXH (+0x20). This only
manifested in earlycon as reg-io-width in the device tree is consulted
for normal serial writes.

Change the iotype of the port to UPIO_MEM32, to allow the serial port to
function on A7-A11 SoCs. This change does not appear to affect Apple M1 and
above.

Signed-off-by: Nick Chan <towinchenmi@...il.com>
---
 drivers/tty/serial/samsung_tty.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index c4f2ac9518aa..27b8a50bd3e7 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -2536,7 +2536,7 @@ static const struct s3c24xx_serial_drv_data s5l_serial_drv_data = {
 		.name		= "Apple S5L UART",
 		.type		= TYPE_APPLE_S5L,
 		.port_type	= PORT_8250,
-		.iotype		= UPIO_MEM,
+		.iotype		= UPIO_MEM32,
 		.fifosize	= 16,
 		.rx_fifomask	= S3C2410_UFSTAT_RXMASK,
 		.rx_fifoshift	= S3C2410_UFSTAT_RXSHIFT,
@@ -2825,8 +2825,10 @@ static int __init apple_s5l_early_console_setup(struct earlycon_device *device,
 	/* Close enough to S3C2410 for earlycon... */
 	device->port.private_data = &s3c2410_early_console_data;
 
+	/* ... however, we need to change the port iotype */
+	device->port.iotype = UPIO_MEM32;
 #ifdef CONFIG_ARM64
-	/* ... but we need to override the existing fixmap entry as nGnRnE */
+	/* ... and also override the existing fixmap entry as nGnRnE */
 	__set_fixmap(FIX_EARLYCON_MEM_BASE, device->port.mapbase,
 		     __pgprot(PROT_DEVICE_nGnRnE));
 #endif
-- 
2.46.0