[U-Boot] [PATCH v4 1/4] mmc: mmc_spi: Use SPI_XFER_BEGIN and SPI_XFER_END flags

[Jagan Teki]

On Tue, Jul 16, 2019 at 1:38 PM Anup Patel <anup at brainfault.org> wrote:
>
> On Tue, Jul 16, 2019 at 1:05 PM Jagan Teki <jagan at amarulasolutions.com> wrote:
> >
> > On Tue, Jul 16, 2019 at 9:52 AM Anup Patel <Anup.Patel at wdc.com> wrote:
> > >
> > > Most DM based SPI host controller drivers use SPI_XFER_BEGIN and
> > > SPI_XFER_END flags to enable/disable slave chip select.
> > >
> > > This patch extends MMC SPI driver to pass SPI_XFER_BEGIN flag when
> > > MMC command is send at start and pass SPI_XFER_END flag using a
> > > dummy transfer (of bitlen = 0) at the end of MMC command.
> > >
> > > Suggested-by: Jagan Teki <jagan at amarulasolutions.com>
> > > Signed-off-by: Anup Patel <anup.patel at wdc.com>
> > > ---
> > >  drivers/mmc/mmc_spi.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/mmc/mmc_spi.c b/drivers/mmc/mmc_spi.c
> > > index f3d687ae80..350812a04b 100644
> > > --- a/drivers/mmc/mmc_spi.c
> > > +++ b/drivers/mmc/mmc_spi.c
> > > @@ -84,7 +84,7 @@ static int mmc_spi_sendcmd(struct udevice *dev,
> > >         cmdo[4] = cmdarg >> 8;
> > >         cmdo[5] = cmdarg;
> > >         cmdo[6] = (crc7(0, &cmdo[1], 5) << 1) | 0x01;
> > > -       ret = dm_spi_xfer(dev, sizeof(cmdo) * 8, cmdo, NULL, 0);
> > > +       ret = dm_spi_xfer(dev, sizeof(cmdo) * 8, cmdo, NULL, SPI_XFER_BEGIN);
> > >         if (ret)
> > >                 return ret;
> > >
> > > @@ -360,6 +360,8 @@ static int dm_mmc_spi_request(struct udevice *dev, struct mmc_cmd *cmd,
> > >         }
> > >
> > >  done:
> > > +       dm_spi_xfer(dev, 0, NULL, NULL, SPI_XFER_END);
> > > +
> >
> > Look like this driver has several dm_spi_xfer in their won sequence,
> > have you tried of sending command and buf in same spi_xfer call so
> > dout and din can be NULL based on the read and write? if ie possible
> > we can manage the transfer flags in single sub call based on data_len
> > like drivers/mtd/spi/sf.c does.
>
> MMC SPI protocol is very different compared to SPI serial flash.
>
> We have to poll for expected byte pattern when waiting for transfer/command
> to complete. We don't know in-advance how many bytes we will have to read.

Yes, so we begin the transfer and end if successful is it? apart from
this we also need to provide claim and release calls from here,
so-that the sifive spi can handle them accordingly otherwise using
sifive spi may not work with flash.