| Message ID | 20230310092053.1006459-2-l.goehrs@pengutronix.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 1e4929112507f145951f4c356161ab80ad9c1f0e |
| Headers | show |
| Series | [v1,1/2] spi: core: add spi_split_transfers_maxwords | expand |
Hi Leonard, thanks for your patch. I agree with this patch and tested it ok as well on my side. On Fri, Mar 10, 2023 at 10:20:53AM +0100, Leonard Göhrs wrote: > The TSIZE register in CR2, to which the number of words to transfer > is written, is only 16 Bit. This limits transfers to 65535 SPI > _words_ at a time. The existing code uses spi_split_transfers_maxsize > to limit transfers to 65535 _bytes_ at a time. > > This breaks large transfers with bits_per_word > 8, as they are > split inside of a word boundary by the odd size limit. > > Split transfers based on the number of words instead. > This has the added benefit of not artificially limiting the maximum > length of bpw > 8 transfers to half or a quarter of the actual limit. > > The combination of very large transfers and bits_per_word = 16 is triggered > e.g. by MIPI DBI displays when updating large parts of the screen. > > Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de> > --- > drivers/spi/spi-stm32.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c > index def09cf0dc14..d2e16f16fae6 100644 > --- a/drivers/spi/spi-stm32.c > +++ b/drivers/spi/spi-stm32.c > @@ -984,9 +984,9 @@ static int stm32_spi_prepare_msg(struct spi_master *master, > if (spi->cfg->set_number_of_data) { > int ret; > > - ret = spi_split_transfers_maxsize(master, msg, > - STM32H7_SPI_TSIZE_MAX, > - GFP_KERNEL | GFP_DMA); > + ret = spi_split_transfers_maxwords(master, msg, > + STM32H7_SPI_TSIZE_MAX, > + GFP_KERNEL | GFP_DMA); > if (ret) > return ret; > } Acked-by: Alain Volmat <alain.volmat@foss.st.com> > -- > 2.30.2 >
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c index def09cf0dc14..d2e16f16fae6 100644 --- a/drivers/spi/spi-stm32.c +++ b/drivers/spi/spi-stm32.c @@ -984,9 +984,9 @@ static int stm32_spi_prepare_msg(struct spi_master *master, if (spi->cfg->set_number_of_data) { int ret; - ret = spi_split_transfers_maxsize(master, msg, - STM32H7_SPI_TSIZE_MAX, - GFP_KERNEL | GFP_DMA); + ret = spi_split_transfers_maxwords(master, msg, + STM32H7_SPI_TSIZE_MAX, + GFP_KERNEL | GFP_DMA); if (ret) return ret; }
The TSIZE register in CR2, to which the number of words to transfer is written, is only 16 Bit. This limits transfers to 65535 SPI _words_ at a time. The existing code uses spi_split_transfers_maxsize to limit transfers to 65535 _bytes_ at a time. This breaks large transfers with bits_per_word > 8, as they are split inside of a word boundary by the odd size limit. Split transfers based on the number of words instead. This has the added benefit of not artificially limiting the maximum length of bpw > 8 transfers to half or a quarter of the actual limit. The combination of very large transfers and bits_per_word = 16 is triggered e.g. by MIPI DBI displays when updating large parts of the screen. Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de> --- drivers/spi/spi-stm32.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)