[PATCH] [RFC] spi: pxa2xx: Do cs if restart the SSP during pxa2xx_spi_transfer_one()

From: xiao jin
Date: Thu Mar 07 2019 - 02:13:33 EST

The spi-pxa2xx can't read and write data correctly on our board.
The pxa_ssp_type is LPSS_BXT_SSP in our case.

With more debug we find that it's related to restart the SPP
during pxa2xx_spi_transfer_one().

In the normal case the spi_transfer_one_message() calls spi-pxa2xx
cs_assert before transferring one message. After completing the
transfer it calls spi-pxa2xx cs_deassert. The spi-pxa2xx works

But in some other case pxa2xx_spi_unprepare_transfer() is called
that clears SSCR0_SSE bit before the next transfer. In the next
transfer the spi-pxa2xx driver will restart the SSP as the SSE
bit is cleared. The cs_assert before the SSP restart can't ensure
spi-pxa2xx work well.

The patch is to do cs again if spi-pxa2xx restar the SSP during

Signed-off-by: xiao jin <jin.xiao@xxxxxxxxx>
Signed-off-by: he, bo <bo.he@xxxxxxxxx>
drivers/spi/spi-pxa2xx.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index 14f4ea59caff..1a2ea46858d9 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -928,6 +928,7 @@ static int pxa2xx_spi_transfer_one(struct spi_controller *master,
u32 cr1;
int err;
int dma_mapped;
+ bool need_cs_change = false;

/* Check if we can DMA this transfer */
if (transfer->len > MAX_DMA_LEN && chip->enable_dma) {
@@ -1056,6 +1057,11 @@ static int pxa2xx_spi_transfer_one(struct spi_controller *master,
if ((pxa2xx_spi_read(drv_data, SSCR0) != cr0)
|| (pxa2xx_spi_read(drv_data, SSCR1) & change_mask)
!= (cr1 & change_mask)) {
+ /* It needs to deassert the chip selection
+ * firstly before restart the SPP */
+ need_cs_change = true;
+ cs_deassert(spi);
/* stop the SSP, and update the other bits */
pxa2xx_spi_write(drv_data, SSCR0, cr0 & ~SSCR0_SSE);
if (!pxa25x_ssp_comp(drv_data))
@@ -1070,6 +1076,8 @@ static int pxa2xx_spi_transfer_one(struct spi_controller *master,
pxa2xx_spi_write(drv_data, SSTO, chip->timeout);

+ if (need_cs_change)
+ cs_assert(spi);
* Release the data by enabling service requests and interrupts,
* without changing any mode bits