Messages in this thread | | | Subject | Re: [PATCH] [RFC] spi: pxa2xx: Do cs if restart the SSP during pxa2xx_spi_transfer_one() | From | Jarkko Nikula <> | Date | Thu, 7 Mar 2019 17:26:53 +0200 |
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Hi
Is this also related to the regression with d5898e19c0d7 ("spi: pxa2xx: Use core message processing loop") you have found or another issue?
Comments below.
On 3/7/19 9:24 AM, xiao jin wrote: > 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 > well. > > 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 > pxa2xx_spi_transfer_one() > Hmm.. please correct me if I'm wrong but pxa2xx_spi_unprepare_transfer() is called always when there is no more messages pending and the spi core should have deasserted the CS already?
More below.
> Signed-off-by: xiao jin <jin.xiao@intel.com> > Signed-off-by: he, bo <bo.he@intel.com> > --- > 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); > +
I think code comes here at the beginning of each transfer so will be hit multiple times before pxa2xx_spi_unprepare_transfer() if SPI message consists of multiple transfers.
This makes me wondering if the device driver setting up the "struct spi_transfer" is maybe missing the cs_change flag set for transfers before last one in case HW needs CS toggling between transfers? For instance what following drivers are doing with the cs_change flag:
drivers/char/tpm/tpm_tis_spi.c: tpm_tis_spi_transfer() drivers/input/touchscreen/ad7877.c: ad7877_read(), ad7877_read_adc()
-- Jarkko
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