linux-kernel - Re: [PATCH v3 6/6] sdhci: tegra: Add missing TMCLK for data timeout

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Date:   Mon, 24 Aug 2020 09:58:25 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jon Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "# 4.0+" <stable@...r.kernel.org>
Subject: Re: [PATCH v3 6/6] sdhci: tegra: Add missing TMCLK for data timeout

On Thu, 6 Aug 2020 at 02:32, Sowjanya Komatineni <skomatineni@...dia.com> wrote:
>
> commit b5a84ecf025a ("mmc: tegra: Add Tegra210 support")
>
> Tegra210 and later has a separate sdmmc_legacy_tm (TMCLK) used by Tegra
> SDMMC hawdware for data timeout to achive better timeout than using
> SDCLK and using TMCLK is recommended.
>
> USE_TMCLK_FOR_DATA_TIMEOUT bit in Tegra SDMMC register
> SDHCI_TEGRA_VENDOR_SYS_SW_CTRL can be used to choose either TMCLK or
> SDCLK for data timeout.
>
> Default USE_TMCLK_FOR_DATA_TIMEOUT bit is set to 1 and TMCLK is used
> for data timeout by Tegra SDMMC hardware and having TMCLK not enabled
> is not recommended.
>
> So, this patch fixes it.

Just realized that there should be an updated DT binding accordingly,
stating that the "tmclk" is recommended but optional for some
variants. Please re-spin.

Kind regards
Uffe

>
> Fixes: b5a84ecf025a ("mmc: tegra: Add Tegra210 support")
> Cc: stable <stable@...r.kernel.org> # 5.4
> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 31ed321..c0b9405 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -140,6 +140,7 @@ struct sdhci_tegra_autocal_offsets {
>  struct sdhci_tegra {
>         const struct sdhci_tegra_soc_data *soc_data;
>         struct gpio_desc *power_gpio;
> +       struct clk *tmclk;
>         bool ddr_signaling;
>         bool pad_calib_required;
>         bool pad_control_available;
> @@ -1611,6 +1612,44 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
>                 goto err_power_req;
>         }
>
> +       /*
> +        * Tegra210 has a separate SDMMC_LEGACY_TM clock used for host
> +        * timeout clock and SW can choose TMCLK or SDCLK for hardware
> +        * data timeout through the bit USE_TMCLK_FOR_DATA_TIMEOUT of
> +        * the register SDHCI_TEGRA_VENDOR_SYS_SW_CTRL.
> +        *
> +        * USE_TMCLK_FOR_DATA_TIMEOUT bit default is set to 1 and SDMMC uses
> +        * 12Mhz TMCLK which is advertised in host capability register.
> +        * With TMCLK of 12Mhz provides maximum data timeout period that can
> +        * be achieved is 11s better than using SDCLK for data timeout.
> +        *
> +        * So, TMCLK is set to 12Mhz and kept enabled all the time on SoC's
> +        * supporting SDR104 mode and when not using SDCLK for data timeout.
> +        */
> +
> +       if ((soc_data->nvquirks & NVQUIRK_ENABLE_SDR104) &&
> +           !(soc_data->pdata->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)) {
> +               clk = devm_clk_get(&pdev->dev, "tmclk");
> +               if (IS_ERR(clk)) {
> +                       rc = PTR_ERR(clk);
> +                       if (rc == -EPROBE_DEFER)
> +                               goto err_power_req;
> +
> +                       dev_warn(&pdev->dev, "failed to get tmclk: %d\n", rc);
> +                       clk = NULL;
> +               }
> +
> +               clk_set_rate(clk, 12000000);
> +               rc = clk_prepare_enable(clk);
> +               if (rc) {
> +                       dev_err(&pdev->dev,
> +                               "failed to enable tmclk: %d\n", rc);
> +                       goto err_power_req;
> +               }
> +
> +               tegra_host->tmclk = clk;
> +       }
> +
>         clk = devm_clk_get(mmc_dev(host->mmc), NULL);
>         if (IS_ERR(clk)) {
>                 rc = PTR_ERR(clk);
> @@ -1654,6 +1693,7 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
>  err_rst_get:
>         clk_disable_unprepare(pltfm_host->clk);
>  err_clk_get:
> +       clk_disable_unprepare(tegra_host->tmclk);
>  err_power_req:
>  err_parse_dt:
>         sdhci_pltfm_free(pdev);
> @@ -1671,6 +1711,7 @@ static int sdhci_tegra_remove(struct platform_device *pdev)
>         reset_control_assert(tegra_host->rst);
>         usleep_range(2000, 4000);
>         clk_disable_unprepare(pltfm_host->clk);
> +       clk_disable_unprepare(tegra_host->tmclk);
>
>         sdhci_pltfm_free(pdev);
>
> --
> 2.7.4
>