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From: Sai Pavan Boddu <sai.pavan.boddu@amd.com>
To: <linux-kernel@vger.kernel.org>, <linux-i2c@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>
Cc: Michal Simek <michal.simek@amd.com>,
	Andi Shyti <andi.shyti@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Wolfram Sang <wsa@kernel.org>
Subject: [PATCH] i2c: cadence: Avoid fifo clear after start
Date: Fri, 5 Jan 2024 18:22:58 +0530	[thread overview]
Message-ID: <20240105125258.2470397-1-sai.pavan.boddu@amd.com> (raw)

Driver unintentionally programs ctrl reg to clear fifo which is
happening after start of transaction, this was not the case previously
as it was read-modified-write. This issue breaks i2c reads on QEMU as
i2c-read is done before guest starts programming ctrl register.

Fixes: ff0cf7bca6309 ("i2c: cadence: Remove unnecessary register reads")
Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@amd.com>
---
 drivers/i2c/busses/i2c-cadence.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index de3f58b60dce..6f7d753a8197 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -633,6 +633,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
 
 	if (hold_clear) {
 		ctrl_reg &= ~CDNS_I2C_CR_HOLD;
+		ctrl_reg &= ~CDNS_I2C_CR_CLR_FIFO;
 		/*
 		 * In case of Xilinx Zynq SOC, clear the HOLD bit before transfer size
 		 * register reaches '0'. This is an IP bug which causes transfer size
-- 
2.25.1


             reply	other threads:[~2024-01-05 12:53 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-05 12:52 Sai Pavan Boddu [this message]
2024-01-10 16:00 ` Michal Simek
2024-01-17 13:19 ` Andi Shyti
2024-01-17 18:06   ` Boddu, Sai Pavan
2024-01-17 21:05     ` Andi Shyti
2024-05-03  9:05       ` Boddu, Sai Pavan
2024-05-03 10:48         ` Andi Shyti

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