linux-kernel - [PATCH v3 1/4] i2c: pasemi: Enable the unjam machine

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Message-Id: <20250427-pasemi-fixes-v3-1-af28568296c0@svenpeter.dev>
Date: Sun, 27 Apr 2025 11:30:43 +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>, 
 Neal Gompa <neal@...pa.dev>, Hector Martin <marcan@...can.st>
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>
Subject: [PATCH v3 1/4] 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>
Reviewed-by: Neal Gompa <neal@...pa.dev>
Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
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 df1b0087dcacb0a3b94196368137d5e20b0e6d7e..3f5571a90c1d268ea2a9d95285f1a5e47f0481ff 100644
--- a/drivers/i2c/busses/i2c-pasemi-core.c
+++ b/drivers/i2c/busses/i2c-pasemi-core.c
@@ -71,7 +71,7 @@ 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