linux-kernel - RE: [PATCH v2] mmc: sdhci-tegra: Fix switch to HS400ES mode

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Date:   Mon, 6 Dec 2021 14:06:33 +0000
From:   Prathamesh Shete <pshete@...dia.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Aniruddha Tvs Rao <anrao@...dia.com>,
        Suresh Mangipudi <smangipudi@...dia.com>
Subject: RE: [PATCH v2] mmc: sdhci-tegra: Fix switch to HS400ES mode

Thanks for review!
Updated the programming sequence and Pushed version v3.

Thanks
Prathamesh.

> -----Original Message-----
> From: Adrian Hunter <adrian.hunter@...el.com>
> Sent: Thursday, December 2, 2021 8:05 PM
> To: Prathamesh Shete <pshete@...dia.com>; ulf.hansson@...aro.org;
> thierry.reding@...il.com; Jonathan Hunter <jonathanh@...dia.com>;
> p.zabel@...gutronix.de; linux-mmc@...r.kernel.org; linux-
> tegra@...r.kernel.org; linux-kernel@...r.kernel.org
> Cc: Aniruddha Tvs Rao <anrao@...dia.com>; Suresh Mangipudi
> <smangipudi@...dia.com>
> Subject: Re: [PATCH v2] mmc: sdhci-tegra: Fix switch to HS400ES mode
> 
> External email: Use caution opening links or attachments
> 
> 
> On 02/12/2021 15:49, Prathamesh Shete wrote:
> > When CMD13 is sent after switching to HS400ES mode, the bus is
> > operating at either MMC_HIGH_26_MAX_DTR or MMC_HIGH_52_MAX_DTR.
> > To meet Tegra SDHCI requirement at HS400ES mode, force SDHCI interface
> > clock to MMC_HS200_MAX_DTR (200 MHz) so that host controller CAR clock
> > and the interface clock are rate matched.
> >
> > Signed-off-by: Prathamesh Shete <pshete@...dia.com>
> > ---
> >  drivers/mmc/host/sdhci-tegra.c | 43
> > ++++++++++++++++++++--------------
> >  1 file changed, 26 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-tegra.c
> > b/drivers/mmc/host/sdhci-tegra.c index 387ce9cdbd7c..ca261cce9b37
> > 100644
> > --- a/drivers/mmc/host/sdhci-tegra.c
> > +++ b/drivers/mmc/host/sdhci-tegra.c
> > @@ -354,23 +354,6 @@ static void tegra_sdhci_set_tap(struct sdhci_host
> *host, unsigned int tap)
> >       }
> >  }
> >
> > -static void tegra_sdhci_hs400_enhanced_strobe(struct mmc_host *mmc,
> > -                                           struct mmc_ios *ios)
> > -{
> > -     struct sdhci_host *host = mmc_priv(mmc);
> > -     u32 val;
> > -
> > -     val = sdhci_readl(host, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
> > -
> > -     if (ios->enhanced_strobe)
> > -             val |= SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
> > -     else
> > -             val &= ~SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
> > -
> > -     sdhci_writel(host, val, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
> > -
> > -}
> > -
> >  static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)  {
> >       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host); @@
> > -791,6 +774,32 @@ static void tegra_sdhci_set_clock(struct sdhci_host *host,
> unsigned int clock)
> >       }
> >  }
> >
> > +static void tegra_sdhci_hs400_enhanced_strobe(struct mmc_host *mmc,
> > +                                           struct mmc_ios *ios) {
> > +     struct sdhci_host *host = mmc_priv(mmc);
> > +     u32 val;
> > +
> > +     val = sdhci_readl(host, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
> > +
> > +     if (ios->enhanced_strobe)
> > +             val |= SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
> > +     else
> > +             val &= ~SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
> > +
> > +     sdhci_writel(host, val, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
> > +
> > +     /*
> > +      * When CMD13 is sent from mmc_select_hs400es() after
> > +      * switching to HS400ES mode, the bus is operating at
> > +      * either MMC_HIGH_26_MAX_DTR or MMC_HIGH_52_MAX_DTR.
> > +      * To meet Tegra SDHCI requirement at HS400ES mode, force SDHCI
> > +      * interface clock to MMC_HS200_MAX_DTR (200 MHz) so that host
> > +      * controller CAR clock and the interface clock are rate matched.
> 
> Still doesn't explain why you want to set MMC_HS200_MAX_DTR when
> ios->enhanced_strobe is false e.g. mmc_set_initial_state()
That’s a good catch. Updated the code sequence and pushed v3.


> > +      */
> > +     tegra_sdhci_set_clock(host, MMC_HS200_MAX_DTR); }
> > +
> >  static unsigned int tegra_sdhci_get_max_clock(struct sdhci_host
> > *host)  {
> >       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> >