From: dillon min <dillon.minfei@xxxxxxxxx>
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@xxxxxxxxx>
---
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
