[PATCH v2 3/3] mmc: renesas-sdhi: Do not access SCC during tuning in send_cmd callback

[Jaehoon Chung]

On 2/25/24 07:32, Marek Vasut wrote:
> Do not access SCC when sending commands during tuning operation as that
> will disrupt the tuning operation. The tuning operation is adjusting the
> SCC settings itself in execute_tuning callback.
> 
> When renesas_sdhi_execute_tuning() is called by the MMC core code, a loop
> which consists of renesas_sdhi_prepare_tuning(), mmc_send_tuning() and
> renesas_sdhi_compare_scc_data() iterates over each SCC tuning tap.
> 
> The renesas_sdhi_prepare_tuning() configures the SCC tuning tap number into
> hardware, mmc_send_tuning() triggers transfer of tuning block which depends
> on the bus mode for which the bus is currently being tuned, this information
> is supplied by the MMC core code, and finally renesas_sdhi_compare_scc_data()
> tests the received tuning block for validity.
> 
> Because renesas_sdhi_prepare_tuning() configures the SCC tuning tap into
> the hardware to fit the tuning operation, mmc_send_tuning() which triggers
> command transfer using renesas_sdhi_send_cmd() must not manipulate with
> the SCC in any way. Currently renesas_sdhi_send_cmd() does unconditionally
> call renesas_sdhi_check_scc_error(), which may adjust the SCC tuning tap
> position by writing RENESAS_SDHI_SCC_TAPSET, which would overwrite the
> required tuning configuration set by renesas_sdhi_prepare_tuning() and
> disrupt the tuning operation.
> 
> Fix this by skipping the renesas_sdhi_check_scc_error() call in case the
> MMC subsystem is in tuning state. This way, the SCC settings are left
> unmodified by command transfer during tuning operation.
> 
> Reviewed-by: Paul Barker <paul.barker.ct at bp.renesas.com>
> Tested-by: Paul Barker <paul.barker.ct at bp.renesas.com>
> Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>

Reviewed-by: Jaehoon Chung <jh80.chung at samsung.com>

Best Regards,
Jaehoon Chung

> ---
> Cc: Hai Pham <hai.pham.ud at renesas.com>
> Cc: Jaehoon Chung <jh80.chung at samsung.com>
> Cc: Nobuhiro Iwamatsu <iwamatsu at nigauri.org>
> Cc: Paul Barker <paul.barker.ct at bp.renesas.com>
> Cc: Peng Fan <peng.fan at nxp.com>
> Cc: Sean Anderson <seanga2 at gmail.com>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh at renesas.com>
> ---
> V2: Add RB/TB from Paul
> ---
>  drivers/mmc/renesas-sdhi.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/renesas-sdhi.c b/drivers/mmc/renesas-sdhi.c
> index 29a742f404e..c4d0733b621 100644
> --- a/drivers/mmc/renesas-sdhi.c
> +++ b/drivers/mmc/renesas-sdhi.c
> @@ -798,9 +798,12 @@ static int renesas_sdhi_send_cmd(struct udevice *dev, struct mmc_cmd *cmd,
>  #if CONFIG_IS_ENABLED(MMC_UHS_SUPPORT) || \
>      CONFIG_IS_ENABLED(MMC_HS200_SUPPORT) || \
>      CONFIG_IS_ENABLED(MMC_HS400_SUPPORT)
> +	struct mmc_uclass_priv *upriv = dev_get_uclass_priv(dev);
>  	struct tmio_sd_priv *priv = dev_get_priv(dev);
> +	struct mmc *mmc = upriv->mmc;
>  
> -	renesas_sdhi_check_scc_error(dev);
> +	if (!mmc->tuning)
> +		renesas_sdhi_check_scc_error(dev);
>  
>  	if (cmd->cmdidx == MMC_CMD_SEND_STATUS)
>  		renesas_sdhi_adjust_hs400_mode_enable(priv);