linux-kernel - Re: [PATCH v2 6/6] sdhci: tegra: Add missing TMCLK for data timeout

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Date:   Wed, 5 Aug 2020 11:06:30 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        ulf.hansson@...aro.org, thierry.reding@...il.com,
        jonathanh@...dia.com, robh+dt@...nel.org
Cc:     devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Subject: Re: [PATCH v2 6/6] sdhci: tegra: Add missing TMCLK for data timeout

On 4/08/20 7:29 am, Sowjanya Komatineni wrote:
> commit b5a84ecf025a ("mmc: tegra: Add Tegra210 support")

So that could be a Fixes tag also?

> 
> 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.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>

Acked-by: Adrian Hunter <adrian.hunter@...el.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);
>  
>