RE: [PATCH 2/2] mmc: renesas_sdhi: avoid bad TAP in HS400

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Hi Wolfram-san,

Thank you for the patch!

> From: Wolfram Sang, Sent: Wednesday, April 22, 2020 9:59 PM
> To: linux-mmc@xxxxxxxxxxxxxxx
> Cc: linux-renesas-soc@xxxxxxxxxxxxxxx; Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>; Takeshi Saito
> <takeshi.saito.xv@xxxxxxxxxxx>; Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
> Subject: [PATCH 2/2] mmc: renesas_sdhi: avoid bad TAP in HS400
> 
> From: Takeshi Saito <takeshi.saito.xv@xxxxxxxxxxx>
> 
> With R-Car Gen3, CRC error occue at the following TAPs.
> 
> H3, M3W 1.3, M3N... TAP=2,3,6,7
> M3W 3.0		... TAP=1,3,5,7
> 
> (Note: for 4tap SoCs, the numbers get divided by 2)
> 
> Do not use these TAPs in HS400, and also don't use auto correction but
> manual correction.
> 
> We check for bad taps in two places:
> 
> 1) After tuning HS400: Then, we select a neighbouring TAP. One of them
>    must be good, because there are never three bad taps in a row.
>    Retuning won't help because we just finished tuning.
> 
> 2) After a manual correction request: Here, we can't switch to the
>    requested TAP. But we can retune (if the HS200 tuning was good)
>    because the environment might have changed since the last tuning.
>    If not, we stay on the same TAP.
> 
> Signed-off-by: Takeshi Saito <takeshi.saito.xv@xxxxxxxxxxx>
> [wsa: refactored to match upstream driver, reworded commit msg]
> Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/mmc/host/renesas_sdhi.h      |  1 +
>  drivers/mmc/host/renesas_sdhi_core.c | 56 ++++++++++++++++++++++++----
>  2 files changed, 49 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mmc/host/renesas_sdhi.h b/drivers/mmc/host/renesas_sdhi.h
> index 86efa9d5cd6d..14c64caefc64 100644
> --- a/drivers/mmc/host/renesas_sdhi.h
> +++ b/drivers/mmc/host/renesas_sdhi.h
> @@ -36,6 +36,7 @@ struct renesas_sdhi_of_data {
>  struct renesas_sdhi_quirks {
>  	bool hs400_disabled;
>  	bool hs400_4taps;
> +	u32 hs400_bad_taps;
>  };
> 
>  struct tmio_mmc_dma {
> diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
> index 33b51105c788..4fee26e6b66c 100644
> --- a/drivers/mmc/host/renesas_sdhi_core.c
> +++ b/drivers/mmc/host/renesas_sdhi_core.c
> @@ -325,6 +325,8 @@ static void renesas_sdhi_hs400_complete(struct mmc_host *mmc)
>  {
>  	struct tmio_mmc_host *host = mmc_priv(mmc);
>  	struct renesas_sdhi *priv = host_to_priv(host);
> +	u32 bad_taps = priv->quirks ? priv->quirks->hs400_bad_taps : 0;
> +	bool use_4tap = priv->quirks && priv->quirks->hs400_4taps;
> 
>  	sd_ctrl_write16(host, CTL_SD_CARD_CLK_CTL, ~CLK_CTL_SCLKEN &
>  		sd_ctrl_read16(host, CTL_SD_CARD_CLK_CTL));
> @@ -352,10 +354,24 @@ static void renesas_sdhi_hs400_complete(struct mmc_host *mmc)
>  		       SH_MOBILE_SDHI_SCC_DTCNTL_TAPEN |
>  		       0x4 << SH_MOBILE_SDHI_SCC_DTCNTL_TAPNUM_SHIFT);
> 
> +	/* Avoid bad TAP */
> +	if (bad_taps & BIT(priv->tap_set)) {
> +		u32 new_tap = (priv->tap_set + 1) % priv->tap_num;
> +
> +		if (bad_taps & BIT(new_tap)) {
> +			new_tap = (priv->tap_set - 1) % priv->tap_num;
> +		}

I think we can remove the braces.
After removed it,

Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>

Best regards,
Yoshihiro Shimoda





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