[PATCH AUTOSEL 4.19 32/38] i2c: stm32f7: fix first byte to send in slave mode

[PATCH AUTOSEL 4.19 32/38] i2c: stm32f7: fix first byte to send in slave mode

[Sasha Levin]

From: Fabrice Gasnier <fabrice.gasnier@st.com>

[ Upstream commit 02e64276c6dbcc4c5f39844f33d18180832a58f3 ]

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.

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

Fixes: 60d609f30de2 ("i2c: i2c-stm32f7: Add slave support")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 ac9c9486b834c..48521bc8a4d23 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -1177,6 +1177,8 @@ 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);
-- 
2.20.1

[PATCH AUTOSEL 4.19 33/38] i2c: stm32f7: fix a race in slave mode with arbitration loss irq

[Sasha Levin]

From: Fabrice Gasnier <fabrice.gasnier@st.com>

[ Upstream commit 6d6b0d0d5afc8c4c84b08261260ba11dfa5206f2 ]

When in slave mode, an arbitration loss (ARLO) may be detected before the
slave had a chance to detect the stop condition (STOPF in ISR).
This is seen when two master + slave adapters switch their roles. It
provokes the i2c bus to be stuck, busy as SCL line is stretched.
- the I2C_SLAVE_STOP event is never generated due to STOPF flag is set but
  don't generate an irq (race with ARLO irq, STOPIE is masked). STOPF flag
  remains set until next master xfer (e.g. when STOPIE irq get unmasked).
  In this case, completion is generated too early: immediately upon new
  transfer request (then it doesn't send all data).
- Some data get stuck in TXDR register. As a consequence, the controller
  stretches the SCL line: the bus gets busy until a future master transfer
  triggers the bus busy / recovery mechanism (this can take time... and
  may never happen at all)

So choice is to let the STOPF being detected by the slave isr handler,
to properly handle this stop condition. E.g. don't mask IRQs in error
handler, when the slave is running.

Fixes: 60d609f30de2 ("i2c: i2c-stm32f7: Add slave support")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/i2c/busses/i2c-stm32f7.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 48521bc8a4d23..362b23505f214 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -1488,7 +1488,7 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
 	void __iomem *base = i2c_dev->base;
 	struct device *dev = i2c_dev->dev;
 	struct stm32_i2c_dma *dma = i2c_dev->dma;
-	u32 mask, status;
+	u32 status;
 
 	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
 
@@ -1513,12 +1513,15 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
 		f7_msg->result = -EINVAL;
 	}
 
-	/* Disable interrupts */
-	if (stm32f7_i2c_is_slave_registered(i2c_dev))
-		mask = STM32F7_I2C_XFER_IRQ_MASK;
-	else
-		mask = STM32F7_I2C_ALL_IRQ_MASK;
-	stm32f7_i2c_disable_irq(i2c_dev, mask);
+	if (!i2c_dev->slave_running) {
+		u32 mask;
+		/* Disable interrupts */
+		if (stm32f7_i2c_is_slave_registered(i2c_dev))
+			mask = STM32F7_I2C_XFER_IRQ_MASK;
+		else
+			mask = STM32F7_I2C_ALL_IRQ_MASK;
+		stm32f7_i2c_disable_irq(i2c_dev, mask);
+	}
 
 	/* Disable dma */
 	if (i2c_dev->use_dma) {
-- 
2.20.1

[PATCH AUTOSEL 4.19 34/38] i2c: stm32f7: remove warning when compiling with W=1

[Sasha Levin]

From: Alain Volmat <alain.volmat@st.com>

[ Upstream commit 348e46fbb4cdb2aead79aee1fd8bb25ec5fd25db ]

Remove the following warning:

drivers/i2c/busses/i2c-stm32f7.c:315:
warning: cannot understand function prototype:
'struct stm32f7_i2c_spec i2c_specs[] =

Replace a comment starting with /** by simply /* to avoid having
it interpreted as a kernel-doc comment.

Fixes: aeb068c57214 ("i2c: i2c-stm32f7: add driver")
Signed-off-by: Alain Volmat <alain.volmat@st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/i2c/busses/i2c-stm32f7.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 362b23505f214..f4e3613f9361b 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -297,7 +297,7 @@ struct stm32f7_i2c_dev {
 	bool use_dma;
 };
 
-/**
+/*
  * All these values are coming from I2C Specification, Version 6.0, 4th of
  * April 2014.
  *
-- 
2.20.1