linux-kernel - Re: [PATCH v2] mmc: sdhci-acpi: Fix HS400 tuning for AMDI0040

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Date:   Fri, 21 Aug 2020 08:24:22 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Raul E Rangel <rrangel@...omium.org>
Cc:     adrian.hunter@...el.com, Akshu.Agrawal@....com, chris.wang@....com,
        Nehal-bakulchandra.Shah@....com,
        Ulf Hansson <ulf.hansson@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>, linux-mmc@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v2] mmc: sdhci-acpi: Fix HS400 tuning for AMDI0040

On Thu, Aug 20, 2020 at 3:00 AM Raul E Rangel <rrangel@...omium.org> wrote:
>
> The AMD eMMC Controller can only use the tuned clock while in HS200 and
> HS400 mode. If we switch to a different mode, we need to disable the
> tuned clock. If we have previously performed tuning and switch back to
> HS200 or HS400, we can re-enable the tuned clock.
>
> Previously the tuned clock was not getting disabled when switching to
> DDR52 which is part of the HS400 tuning sequence.
>
> Fixes: 34597a3f60b1 ("mmc: sdhci-acpi: Add support for ACPI HID of AMD Controller with HS400")
> Signed-off-by: Raul E Rangel <rrangel@...omium.org>
> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>
> Changes in v2:
> - Added static to amd_sdhci_execute_tuning
>
>  drivers/mmc/host/sdhci-acpi.c | 68 +++++++++++++++++++++++++++++------
>  1 file changed, 58 insertions(+), 10 deletions(-)
[snip]
> +               /* DLL is only required for HS400 */
> +               if (host->timing == MMC_TIMING_MMC_HS400 &&
> +                   !amd_host->dll_enabled) {
> +                       trace_printk("%s: Enabling DLL\n", __func__);

Please do not use trace_printk in production code [1,2], it is only
meant for debug use. Consider using dev_dbg.

[1] https://elixir.bootlin.com/linux/v5.8/source/kernel/trace/trace.c#L3158
[2] https://elixir.bootlin.com/linux/v5.8/source/include/linux/kernel.h#L766

> +                       sdhci_acpi_amd_hs400_dll(host);
> +                       amd_host->dll_enabled = true;
> +               }
>         }