linux-kernel - Re: [v4 3/3] mmc: sdhci-cadence: Update PHY delay configuration

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Date:   Wed, 22 Mar 2017 16:24:03 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Piotr Sroka <piotrs@...ence.com>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v4 3/3] mmc: sdhci-cadence: Update PHY delay configuration

2017-03-22 16:08 GMT+09:00 Piotr Sroka <piotrs@...ence.com>:
> Hi Masahiro
>
> 2017-03-21 08:3 AM  Masahiro Yamada <yamada.masahiro@...ionext.com>:
>> Hi Piotr,
>>
>> 2017-03-21 16:01 GMT+09:00 Piotr Sroka <piotrs@...ence.com>:
>> >
>> > Hi Masahiro
>> >
>> > 2017-03-21 02:46 AM Masahiro Yamada <yamada.masahiro@...ionext.com>:
>> >> Hi Piotr,
>> >>
>> >>
>> >> 2017-03-20 20:20 GMT+09:00 Piotr Sroka <piotrs@...ence.com>:
>> >> > DTS properties are used instead of fixed data
>> >> > because PHY settings can be different for different chips/boards.
>> >> >
>> >> > Signed-off-by: Piotr Sroka <piotrs@...ence.com>
>> >>
>> >>
>> >> I found this version is a problem for me.
>> >>
>> >>
>> >> > +
>> >> > +static const struct sdhci_cdns_phy_cfg sdhci_cdns_phy_cfgs[] = {
>> >> > +       { "cdns,phy-input-delay-sd-highspeed", SDHCI_CDNS_PHY_DLY_SD_HS, },
>> >> > +       { "cdns,phy-input-delay-sd-legacy", SDHCI_CDNS_PHY_DLY_SD_DEFAULT, },
>> >> > +       { "cdns,phy-input-delay-sd-uhs-sdr12", SDHCI_CDNS_PHY_DLY_UHS_SDR12, },
>> >> > +       { "cdns,phy-input-delay-sd-uhs-sdr25", SDHCI_CDNS_PHY_DLY_UHS_SDR25, },
>> >> > +       { "cdns,phy-input-delay-sd-uhs-sdr50", SDHCI_CDNS_PHY_DLY_UHS_SDR50, },
>> >> > +       { "cdns,phy-input-delay-sd-uhs-ddr50", SDHCI_CDNS_PHY_DLY_UHS_DDR50, },
>> >> > +       { "cdns,phy-input-delay-mmc-highspeed", SDHCI_CDNS_PHY_DLY_EMMC_SDR, },
>> >> > +       { "cdns,phy-input-delay-mmc-ddr", SDHCI_CDNS_PHY_DLY_EMMC_DDR, },
>> >> > +       { "cdns,phy-dll-delay-sdclk", SDHCI_CDNS_PHY_DLY_SDCLK, },
>> >> > +       { "cdns,phy-dll-delay-sdclk-hsmmc", SDHCI_CDNS_PHY_DLY_HSMMC, },
>> >> > +       { "cdns,phy-dll-delay-strobe", SDHCI_CDNS_PHY_DLY_STROBE, },
>> >> > +};
>> >> > +
>> >>
>> >>
>> >> I see mmc-legacy property in v1,
>> >> but it is missing now.
>> >>
>> >>
>> >> >  static int sdhci_cdns_write_phy_reg(struct sdhci_cdns_priv *priv,
>> >> >                                     u8 addr, u8 data)
>> >> >  {
>> >> > @@ -90,13 +113,26 @@ static int sdhci_cdns_write_phy_reg(struct sdhci_cdns_priv *priv,
>> >> >         return 0;
>> >> >  }
>> >> >
>> >> > -static void sdhci_cdns_phy_init(struct sdhci_cdns_priv *priv)
>> >> > +static int sdhci_cdns_phy_init(struct device_node *np,
>> >> > +                              struct sdhci_cdns_priv *priv)
>> >> >  {
>> >> > -       sdhci_cdns_write_phy_reg(priv, SDHCI_CDNS_PHY_DLY_SD_HS, 4);
>> >> > -       sdhci_cdns_write_phy_reg(priv, SDHCI_CDNS_PHY_DLY_SD_DEFAULT, 4);
>> >> > -       sdhci_cdns_write_phy_reg(priv, SDHCI_CDNS_PHY_DLY_EMMC_LEGACY, 9);
>> >> > -       sdhci_cdns_write_phy_reg(priv, SDHCI_CDNS_PHY_DLY_EMMC_SDR, 2);
>> >> > -       sdhci_cdns_write_phy_reg(priv, SDHCI_CDNS_PHY_DLY_EMMC_DDR, 3);
>> >>
>> >>
>> >> I need to set SDHCI_CDNS_PHY_DLY_EMMC_LEGACY to 9 for my SoC.
>> >>
>> >> Maybe, do we need a DT property for this, too?
>> >>
>> > I can add it but could you check if you realy need it? There is no selection MMC legacy mode
>> > in this driver.
>> >
>>
>> Ah, you are right.
>>
>> For Linux, SD-Legacy and MMC-Legacy share the same timing flag.
>> The legacy mode is covered by SDHCI_CDNS_PHY_DLY_SD_DEFAULT,
>> so we need not to set SDHCI_CDNS_PHY_DLY_EMMC_LEGACY.
>>
>> So, I have no problem with patch.
>>
>> Reviewed-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>>
>>
>>
>>
>> From here, just my minor comments.
>> The binding should not be too Linux-oriented.
>> Device Tree is hardware description language, and project-neutral from
>> its concept.
>> I wonder if there is a project that handles SD-Legacy and MMC-Legacy separately.
>> I am not sure about this, and I do not have a strong opinion, either.
>>
>> I leave this to you  (and other developers).
>>
>
> Thanks for your comments.
>
> Because patch adding HS400 enhanced strobe support was applied
> for next branch I needed to create v5. BTW I added one extra patch modifing
> probe function as you suggested.
> I also modify binding to be consistent with linux MMC timing names.
> The driver does not use MMC legacy at all so I think there is no need
> to distinguish between SD Legacy and MMC Legacy. So there are no contraindications
> for being consistent with Linux.


OK.  Make sense.



-- 
Best Regards
Masahiro Yamada