Message-ID: <CAMuHMdUoDhZSmD5rxhZ7t_DydsZ13UX3eHD3i-OaxDs9P6awAg@mail.gmail.com>
Date: Fri, 12 Jan 2024 13:29:07 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: wsa+renesas@...g-engineering.com, ulf.hansson@...aro.org, 
	yoshihiro.shimoda.uh@...esas.com, takeshi.saito.xv@...esas.com, 
	masaharu.hayakawa.ry@...esas.com, linux-mmc@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH] mmc: renesas_sdhi: Fix change point of data handling

Hi Claudiu,

On Fri, Jan 12, 2024 at 12:42 PM Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> On latest kernel revisions it has been noticed (on a RZ/G3S system) that
> when booting Linux and root file system is on eMMC, at some point in
> the booting process, when the systemd applications are started, the
> "mmc0: tuning execution failed: -5" message is displayed on console.
> On kernel v6.7-rc5 this is reproducible in 90% of the boots. This was
> missing on the same system with kernel v6.5.0-rc1. It was also noticed on
> kernel revisions v6.6-rcX on a RZ/G2UL based system but not on the kernel
> this fix is based on (v6.7-rc5).
>
> Investigating it on RZ/G3S lead to the conclusion that every time the issue
> is reproduced all the probed TAPs are OK. According to datasheet, when this
> happens the change point of data need to be considered for tuning.
>
> Previous code considered the change point of data happens when the content
> of the SMPCMP register is zero. According to RZ/V2M hardware manual,
> chapter "Change Point of the Input Data" (as this is the most clear
> description that I've found about change point of the input data and all
> RZ hardware manual are similar on this chapter), at the time of tuning,
> data is captured by the previous and next TAPs and the result is stored in
> the SMPCMP register (previous TAP in bits 22..16, next TAP in bits 7..0).
> If there is a mismatch b/w the previous and the next TAPs, it indicates
> that there is a change point of the input data.
>
> To comply with this, the code checks if this mismatch is present and
> updates the priv->smpcmp mask.
>
> This change has been checked on the devices with the following DTSes by
> doing 50 consecutive reboots and checking for the tuning failure message:
> - r9a08g045s33-smarc.dts
> - r8a7742-iwg21d-q7.dts
> - r8a7743-iwg20d-q7.dts
> - r8a7744-iwg20d-q7.dts
> - r8a7745-iwg22d-sodimm.dts
> - r8a77470-iwg23s-sbc.dts
> - r8a774a1-hihope-rzg2m-ex.dts
> - r8a774b1-hihope-rzg2n-ex.dts
> - r8a774c0-ek874.dts
> - r8a774e1-hihope-rzg2h-ex.dts
> - r9a07g043u11-smarc-rzg2ul.dts
> - r9a07g044c2-smarc-rzg2lc.dts
> - r9a07g044l2-smarc-rzg2l.dts
> - r9a07g054l2-smarc-rzv2l.dts
>
> On r8a774a1-hihope-rzg2m-ex, even though the hardware manual doesn't say
> anything special about it in the "Change Point of the Input Data" chapter
> or SMPCMP register description, it has been noticed that although all TAPs
> probed in the tuning process are OK the SMPCMP is zero. For this updated
> the renesas_sdhi_select_tuning() function to use priv->taps in case all
> TAPs are OK.
>
> Fixes: 5fb6bf51f6d1 ("mmc: renesas_sdhi: improve TAP selection if all TAPs are good")
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

Thanks for your patch!

> --- a/drivers/mmc/host/renesas_sdhi_core.c
> +++ b/drivers/mmc/host/renesas_sdhi_core.c
> @@ -641,7 +645,14 @@ static int renesas_sdhi_select_tuning(struct tmio_mmc_host *host)
>          * identifying the change point of data.
>          */
>         if (bitmap_full(priv->taps, taps_size)) {
> -               bitmap = priv->smpcmp;
> +               /*
> +                * On some setups it happens that all TAPS are OK but
> +                * no change point of data. Any tap should be OK for this.
> +                */
> +               if (bitmap_empty(priv->smpcmp, taps_size))
> +                       bitmap = priv->taps;
> +               else
> +                       bitmap = priv->smpcmp;
>                 min_tap_row = 1;

I know nothing about tuning, but should min_tap_row still be 1?
Or can you fall back to the else case if priv->smpcmp is empty?
I.e. can this be simplified to:

    if (!bitmap_empty(priv->smpcmp, taps_size) &&
        bitmap_full(priv->taps, taps_size)) {
            ...
    } else {
            ...
    }

>         } else {
>                 bitmap = priv->taps;
> @@ -706,7 +718,10 @@ static int renesas_sdhi_execute_tuning(struct mmc_host *mmc, u32 opcode)
>                 if (mmc_send_tuning(mmc, opcode, &cmd_error) == 0)
>                         set_bit(i, priv->taps);
>
> -               if (sd_scc_read32(host, priv, SH_MOBILE_SDHI_SCC_SMPCMP) == 0)
> +               val = sd_scc_read32(host, priv, SH_MOBILE_SDHI_SCC_SMPCMP);

The SH_MOBILE_SDHI_SCC_SMPCMP register is read even if its value is
not used below.

> +               cmpngu_data = FIELD_GET(SH_MOBILE_SDHI_SCC_SMPCMP_CMPNGU_DATA, val);
> +               cmpngd_data = FIELD_GET(SH_MOBILE_SDHI_SCC_SMPCMP_CMPNGD_DATA, val);
> +               if (!cmd_error && cmpngu_data != cmpngd_data)
>                         set_bit(i, priv->smpcmp);

So better move the SH_MOBILE_SDHI_SCC_SMPCMP register access
inside the if (), and change the below to else.

>
>                 if (cmd_error)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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