From: Sai Krishna Potthuri <[email protected]>
As part of unprepare_transfer_hardware, SPI controller will be disabled
which will indirectly deassert the CS line. This will create a problem
in some of the devices where message will be transferred with
cs_change flag set(CS should not be deasserted).
As per SPI controller implementation, if SPI controller is disabled then
all output enables are inactive and all pins are set to input mode which
means CS will go to default state high(deassert). This leads to an issue
when core explicitly ask not to deassert the CS (cs_change = 1). This
patch fix the above issue by checking the Slave select status bits from
configuration register before disabling the SPI.
Signed-off-by: Sai Krishna Potthuri <[email protected]>
Signed-off-by: Amit Kumar Mahapatra <[email protected]>
---
BRANCH: mtd/next
---
drivers/spi/spi-cadence.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index b509eefe16a8..e832ae09e0cd 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -69,6 +69,7 @@
#define CDNS_SPI_BAUD_DIV_SHIFT 3 /* Baud rate divisor shift in CR */
#define CDNS_SPI_SS_SHIFT 10 /* Slave Select field shift in CR */
#define CDNS_SPI_SS0 0x1 /* Slave Select zero */
+#define CDNS_SPI_NOSS 0x3C /* No Slave select */
/*
* SPI Interrupt Registers bit Masks
@@ -449,15 +450,20 @@ static int cdns_prepare_transfer_hardware(struct spi_master *master)
* @master: Pointer to the spi_master structure which provides
* information about the controller.
*
- * This function disables the SPI master controller.
+ * This function disables the SPI master controller when no slave selected.
*
* Return: 0 always
*/
static int cdns_unprepare_transfer_hardware(struct spi_master *master)
{
struct cdns_spi *xspi = spi_master_get_devdata(master);
+ u32 ctrl_reg;
- cdns_spi_write(xspi, CDNS_SPI_ER, CDNS_SPI_ER_DISABLE);
+ /* Disable the SPI if slave is deselected */
+ ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR);
+ ctrl_reg = (ctrl_reg & CDNS_SPI_CR_SSCTRL) >> CDNS_SPI_SS_SHIFT;
+ if (ctrl_reg == CDNS_SPI_NOSS)
+ cdns_spi_write(xspi, CDNS_SPI_ER, CDNS_SPI_ER_DISABLE);
return 0;
}
--
2.17.1
On Mon, 6 Jun 2022 11:55:25 +0530, Amit Kumar Mahapatra wrote:
> From: Sai Krishna Potthuri <[email protected]>
>
> As part of unprepare_transfer_hardware, SPI controller will be disabled
> which will indirectly deassert the CS line. This will create a problem
> in some of the devices where message will be transferred with
> cs_change flag set(CS should not be deasserted).
> As per SPI controller implementation, if SPI controller is disabled then
> all output enables are inactive and all pins are set to input mode which
> means CS will go to default state high(deassert). This leads to an issue
> when core explicitly ask not to deassert the CS (cs_change = 1). This
> patch fix the above issue by checking the Slave select status bits from
> configuration register before disabling the SPI.
>
> [...]
Applied to
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next
Thanks!
[1/1] spi: spi-cadence: Fix SPI CS gets toggling sporadically
commit: 21b511ddee09a78909035ec47a6a594349fe3296
All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.
You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.
If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.
Please add any relevant lists and maintainers to the CCs when replying
to this mail.
Thanks,
Mark