linux-kernel - [PATCH 3/4] i2c: pasemi: Enable the unjam machine

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Message-Id: <20250222-pasemi-fixes-v1-3-d7ea33d50c5e@svenpeter.dev>
Date: Sat, 22 Feb 2025 13:38:35 +0000
From: Sven Peter via B4 Relay <devnull+sven.svenpeter.dev@...nel.org>
To: Janne Grunau <j@...nau.net>, Alyssa Rosenzweig <alyssa@...enzweig.io>, 
 Madhavan Srinivasan <maddy@...ux.ibm.com>, 
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, 
 Christophe Leroy <christophe.leroy@...roup.eu>, 
 Naveen N Rao <naveen@...nel.org>, Andi Shyti <andi.shyti@...nel.org>
Cc: linuxppc-dev@...ts.ozlabs.org, asahi@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Sven Peter <sven@...npeter.dev>, 
 Hector Martin <marcan@...can.st>
Subject: [PATCH 3/4] i2c: pasemi: Enable the unjam machine

From: Hector Martin <marcan@...can.st>

The I2C bus can get stuck under some conditions (desync between
controller and device). The pasemi controllers include an unjam feature
that is enabled on reset, but was being disabled by the driver. Keep it
enabled by explicitly setting the UJM bit in the CTL register. This
should help recover the bus from certain conditions, which would
otherwise remain stuck forever.

Signed-off-by: Hector Martin <marcan@...can.st>
Signed-off-by: Sven Peter <sven@...npeter.dev>
---
 drivers/i2c/busses/i2c-pasemi-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-pasemi-core.c b/drivers/i2c/busses/i2c-pasemi-core.c
index 770b86b92a10..8f0ba975172f 100644
--- a/drivers/i2c/busses/i2c-pasemi-core.c
+++ b/drivers/i2c/busses/i2c-pasemi-core.c
@@ -73,7 +73,7 @@ static inline int reg_read(struct pasemi_smbus *smbus, int reg)
 
 static void pasemi_reset(struct pasemi_smbus *smbus)
 {
-	u32 val = (CTL_MTR | CTL_MRR | (smbus->clk_div & CTL_CLK_M));
+	u32 val = (CTL_MTR | CTL_MRR | CTL_UJM | (smbus->clk_div & CTL_CLK_M));
 
 	if (smbus->hw_rev >= 6)
 		val |= CTL_EN;

-- 
2.34.1