linux-kernel - [PATCH V2 4/4] i2c: stm32f4: Fix stmpe811 get xyz data timeout issue

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Date:   Thu,  7 May 2020 19:15:49 +0800
From:   dillon.minfei@...il.com
To:     mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        philippe.schenker@...adex.com
Cc:     linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dillon min <dillon.minfei@...il.com>
Subject: [PATCH V2 4/4] i2c: stm32f4: Fix stmpe811 get xyz data timeout issue

From: dillon min <dillon.minfei@...il.com>

As stm32f429's internal flash is 2Mbytes and compiled kernel
image bigger than 2Mbytes, so we have to load kernel image
to sdram on stm32f429-disco board which has 8Mbytes sdram space.

based on above context, as you knows kernel running on external
sdram is more slower than internal flash. besides, we need read 4
bytes to get touch screen xyz(x, y, pressure) coordinate data in
stmpe811 interrupt.

so, in stm32f4_i2c_handle_rx_done, as i2c read slower than running
in xip mode, have to adjust 'STOP/START bit set time' from last two
bytes to last one bytes. else, will get i2c timeout in reading
touch screen coordinate.

Signed-off-by: dillon min <dillon.minfei@...il.com>
---
 drivers/i2c/busses/i2c-stm32f4.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f4.c b/drivers/i2c/busses/i2c-stm32f4.c
index d6a69df..83004f2 100644
--- a/drivers/i2c/busses/i2c-stm32f4.c
+++ b/drivers/i2c/busses/i2c-stm32f4.c
@@ -439,7 +439,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
 	int i;
 
 	switch (msg->count) {
-	case 2:
+	case 1:
 		/*
 		 * In order to correctly send the Stop or Repeated Start
 		 * condition on the I2C bus, the STOP/START bit has to be set
@@ -454,7 +454,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
 		else
 			stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
 
-		for (i = 2; i > 0; i--)
+		for (i = 1; i > 0; i--)
 			stm32f4_i2c_read_msg(i2c_dev);
 
 		reg = i2c_dev->base + STM32F4_I2C_CR2;
@@ -463,7 +463,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
 
 		complete(&i2c_dev->complete);
 		break;
-	case 3:
+	case 2:
 		/*
 		 * In order to correctly generate the NACK pulse after the last
 		 * received data byte, we have to enable NACK before reading N-2
-- 
2.7.4