Hi Mathieu, On Thu, Apr 10, 2025 at 11:00:19AM +0200, Mathieu Othacehe wrote: >Hello, > >Back in 2019, the init_stream sequence was disabled with db52e19ced because: > > This is not required. The MMC core sends CMD0 right after the > initialization and it serves the same purpose. > >That is wrong. It does not serve the same purpose at all. The init_stream >function role is to keep the CMD line high for 74 clock cycles which is >required by the SD specification[1]: > > A device shall be ready to accept the first command within 1ms from > detecting VDD min. > Device may use up to 74 clocks for preparation before receiving the first > command. > >It turns out that one of the devices I am speaking to is requiring those 74 >clocks sequence before the send of the CMD0 as described in the specification. > >It was then broken since 2019. > >I guess that most of the other devices out there are able to cope with those >74 clocks sequence missing and can respond directly to CMD0, which is why that >went unnoticed with the omap_hsmmc driver users.
This patchset looks good to me. Reviewd-by: Peng Fan <peng....@nxp.com> But before apply the patchset. I would like see whether Jean has any comments. Thanks, Peng > >I am proposing to restore that sequence, which is also used on the Linux side. > >Thanks, > >Mathieu > >[1]: https://academy.cba.mit.edu/classes/networking_communications/SD/SD.pdf > >Jean-Jacques Hiblot (1): > mmc: Add a new callback function to perform the 74 clocks cycle > sequence > >Mathieu Othacehe (1): > mmc: omap_hsmmc: implement send_init_stream callback > > drivers/mmc/mmc-uclass.c | 13 +++++++++++++ > drivers/mmc/mmc.c | 6 ++++++ > drivers/mmc/omap_hsmmc.c | 13 +++++++++++-- > include/mmc.h | 9 +++++++++ > 4 files changed, 39 insertions(+), 2 deletions(-) > >-- >2.47.1 >
