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From:   dillon.minfei@gmail.com
To:     robh+dt@kernel.org, mcoquelin.stm32@gmail.com,
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        dillon min <dillon.minfei@gmail.com>
Subject: [PATCH v4 4/4] i2c: stm32f4: Fix stmpe811 get xyz data timeout issue
Date:   Tue,  9 Jun 2020 21:26:43 +0800
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From: dillon min <dillon.minfei@gmail.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 position' from last
two bytes to last one bytes. else, will get i2c timeout in reading
touch screen coordinate.

to not take side effect, introduce IIC_LAST_BYTE_POS to support xip
kernel or has mmu platform.

Signed-off-by: dillon min <dillon.minfei@gmail.com>
---

V4: indroduce 'IIC_LAST_BYTE_POS' to compatible with xipkernel boot

 drivers/i2c/busses/i2c-stm32f4.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f4.c b/drivers/i2c/busses/i2c-stm32f4.c
index d6a69dfcac3f..97cf42ae7fa0 100644
--- a/drivers/i2c/busses/i2c-stm32f4.c
+++ b/drivers/i2c/busses/i2c-stm32f4.c
@@ -93,6 +93,12 @@
 #define STM32F4_I2C_MAX_FREQ		46U
 #define HZ_TO_MHZ			1000000
 
+#if !defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
+#define IIC_LAST_BYTE_POS 1
+#else
+#define IIC_LAST_BYTE_POS 2
+#endif
+
 /**
  * struct stm32f4_i2c_msg - client specific data
  * @addr: 8-bit slave addr, including r/w bit
@@ -439,7 +445,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
 	int i;
 
 	switch (msg->count) {
-	case 2:
+	case IIC_LAST_BYTE_POS:
 		/*
 		 * 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 +460,7 @@ 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 = IIC_LAST_BYTE_POS; i > 0; i--)
 			stm32f4_i2c_read_msg(i2c_dev);
 
 		reg = i2c_dev->base + STM32F4_I2C_CR2;
@@ -463,7 +469,7 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
 
 		complete(&i2c_dev->complete);
 		break;
-	case 3:
+	case (IIC_LAST_BYTE_POS+1):
 		/*
 		 * 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