Re: [PATCH v4] mmc: litex_mmc: Set mandatory idle clocks before CMD0

["Gabriel L. Somlo" <gsomlo@gmail.com>]

On Tue, May 19, 2026 at 06:24:19AM +0800, Inochi Amaoto wrote:
> On Mon, May 18, 2026 at 06:20:49PM -0400, Gabriel L. Somlo wrote:
> > with this patch on top of today's latest (4d3a2a466b8d), I get
> > (on 64-bit rocketchip with Litex):
> > 
> > [    6.475114] mmc0: invalid bus width
> > [    6.477870] mmc0: error -22 whilst initialising SD card
> > 
> > Thanks,
> > --Gabriel
> > 
> 
> Hi, Gabriel,
> 
> Could you share the board link and build commands? I think I need to
> take a look for why this occurs.
> 
> Regards,
> Inochi

Hi Inochi,

it's the digilent nexys-video board; the command line to build the
bitstream is:

litex-boards/litex_boards/targets/digilent_nexys_video.py --build \
  --cpu-type rocket --cpu-variant linux --cpu-num-cores 4 --cpu-mem-width 2 \
  --sys-clk-freq 50e6 --with-ethernet --with-sdcard --with-sata --sata-gen 1

(for more details see https://github.com/litex-hub/linux-on-litex-rocket)

I've added your patch on top of the LiteX kernel tree at
https://github.com/litex-hub/linux/tree/litex-rebase

and compiled it with:

make clean
make ARCH=riscv CROSS_COMPILE=riscv64-unknown-linux-gnu- litex_rocket_defconfig
make ARCH=riscv CROSS_COMPILE=riscv64-unknown-linux-gnu-

FWIW, your previous versions of the patch did work, and did fix the
issue you were trying to address (which I did notice being a problem
on my configuration :)

Thanks,
--Gabriel
 
> > On Sun, May 17, 2026 at 09:53:23AM +0800, Inochi Amaoto wrote:
> > > The litex_mmc driver assumes the card is already probed in the BIOS
> > > and skip the phy initialization. This will cause the command fail
> > > like the following when the old card is unplugged and then insert
> > > a new card:
> > > 
> > > [   62.923593] litex-mmc f0004000.mmc: Command (cmd 8) error, status -110
> > > [   62.949717] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> > > [   62.976606] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> > > [   63.002516] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> > > [   63.028442] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> > > 
> > > Add required clock settings and initialization for the CMD 0, so it can
> > > probe the new card.
> > > 
> > > Fixes: 92e099104729 ("mmc: Add driver for LiteX's LiteSDCard interface")
> > > Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
> > > ---
> > > Changed from v3:
> > > - https://lore.kernel.org/linux-mmc/20260426112016.1370929-1-inochiama@gmail.com/
> > > 1. Remove patch 1: mmc: litex_mmc: Move litex_mmc_setclk() to bottom for reuse
> > > 2. Use set_ios() callback to apply the clock change.
> > > 
> > > Changed from v2:
> > > - https://lore.kernel.org/linux-mmc/20260424013615.470325-1-inochiama@gmail.com/
> > > 1. Remove the added function forward reference and add a new patch
> > >    for moving litex_mmc_setclk() function
> > > 
> > > Change from v1:
> > > - https://lore.kernel.org/linux-mmc/20260421025052.755471-1-inochiama@gmail.com/
> > > 1. use fsleep to replace udelay
> > > 
> > > Inochi Amaoto (2):
> > >   mmc: litex_mmc: Move litex_mmc_setclk() to bottom for reuse
> > >   mmc: litex_mmc: Set mandatory idle clocks before CMD0
> > > 
> > >  drivers/mmc/host/litex_mmc.c | 37 ++++++++++++++++++++++--------------
> > >  1 file changed, 23 insertions(+), 14 deletions(-)
> > > ---
> > >  drivers/mmc/host/litex_mmc.c | 11 +++++++++++
> > >  1 file changed, 11 insertions(+)
> > > 
> > > diff --git a/drivers/mmc/host/litex_mmc.c b/drivers/mmc/host/litex_mmc.c
> > > index d2f19c2dc673..65d5c728f536 100644
> > > --- a/drivers/mmc/host/litex_mmc.c
> > > +++ b/drivers/mmc/host/litex_mmc.c
> > > @@ -68,6 +68,9 @@
> > >  #define SD_SLEEP_US       5
> > >  #define SD_TIMEOUT_US 20000
> > > 
> > > +#define SD_INIT_DELAY_US  1000
> > > +#define SD_INIT_CLK_HZ    400000
> > > +
> > >  #define SDIRQ_CARD_DETECT    1
> > >  #define SDIRQ_SD_TO_MEM_DONE 2
> > >  #define SDIRQ_MEM_TO_SD_DONE 4
> > > @@ -449,6 +452,9 @@ static void litex_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > >  {
> > >  	struct litex_mmc_host *host = mmc_priv(mmc);
> > > 
> > > +	if (ios->chip_select == MMC_CS_HIGH)
> > > +		ios->clock = SD_INIT_CLK_HZ;
> > > +
> > >  	/*
> > >  	 * NOTE: Ignore any ios->bus_width updates; they occur right after
> > >  	 * the mmc core sends its own acmd6 bus-width change notification,
> > > @@ -459,6 +465,11 @@ static void litex_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> > >  	/* Update sd_clk */
> > >  	if (ios->clock != host->sd_clk)
> > >  		litex_mmc_setclk(host, ios->clock);
> > > +
> > > +	if (ios->chip_select == MMC_CS_HIGH) {
> > > +		litex_write8(host->sdphy + LITEX_PHY_INITIALIZE, 1);
> > > +		fsleep(SD_INIT_DELAY_US);
> > > +	}
> > >  }
> > > 
> > >  static const struct mmc_host_ops litex_mmc_ops = {
> > > --
> > > 2.54.0
> > >