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

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Date:   Tue, 21 Mar 2017 16:32:41 +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

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).




-- 
Best Regards
Masahiro Yamada