linux-kernel - [PATCH] i2c: i2c-stm32f7: fix first byte to send in slave mode

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Message-ID: <1569857281-19419-1-git-send-email-fabrice.gasnier@st.com>
Date:   Mon, 30 Sep 2019 17:28:01 +0200
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     <wsa@...-dreams.de>, <pierre-yves.mordret@...com>
CC:     <alain.volmat@...com>, <alexandre.torgue@...com>,
        <linux-i2c@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <fabrice.gasnier@...com>
Subject: [PATCH] i2c: i2c-stm32f7: fix first byte to send in slave mode

The slave-interface documentation [1] states "the bus driver should
transmit the first byte" upon I2C_SLAVE_READ_REQUESTED slave event:
- 'val': backend returns first byte to be sent
The driver currently ignores the 1st byte to send on this event.

Fixes: 60d609f30de2 ("i2c: i2c-stm32f7: Add slave support")

[1] https://www.kernel.org/doc/Documentation/i2c/slave-interface

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
---
 drivers/i2c/busses/i2c-stm32f7.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 266d1c2..0af9219 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -1192,6 +1192,8 @@ static void stm32f7_i2c_slave_start(struct stm32f7_i2c_dev *i2c_dev)
 			STM32F7_I2C_CR1_TXIE;
 		stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, mask);
 
+		/* Write 1st data byte */
+		writel_relaxed(value, base + STM32F7_I2C_TXDR);
 	} else {
 		/* Notify i2c slave that new write transfer is starting */
 		i2c_slave_event(slave, I2C_SLAVE_WRITE_REQUESTED, &value);
-- 
2.7.4