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Subject: Re: [PATCH v6 7/7] sdhci: tegra: Add missing TMCLK for data timeout
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        <adrian.hunter@intel.com>, <ulf.hansson@linaro.org>,
        <thierry.reding@gmail.com>, <robh+dt@kernel.org>
CC:     <linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-mmc@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <stable@vger.kernel.org>
References: <1598500201-5987-1-git-send-email-skomatineni@nvidia.com>
 <1598500201-5987-8-git-send-email-skomatineni@nvidia.com>
From:   Jon Hunter <jonathanh@nvidia.com>
Message-ID: <93d0188b-c833-33b4-211e-b9293c4f3a1c@nvidia.com>
Date:   Thu, 27 Aug 2020 09:40:06 +0100
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On 27/08/2020 04:50, Sowjanya Komatineni 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 adds quirk NVQUIRK_HAS_TMCLK for SoC having separate
> timeout clock and keeps TMCLK enabled all the time.
> 
> Fixes: b5a84ecf025a ("mmc: tegra: Add Tegra210 support")
> Cc: stable <stable@vger.kernel.org> # 5.4
> Tested-by: Jon Hunter <jonathanh@nvidia.com>
> Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
> Acked-by: Adrian Hunter <adrian.hunter@intel.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 90 ++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 82 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 31ed321..f69ca8d 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -13,6 +13,7 @@
>  #include <linux/clk.h>
>  #include <linux/io.h>
>  #include <linux/of.h>
> +#include <linux/of_clk.h>
>  #include <linux/of_device.h>
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/regulator/consumer.h>
> @@ -110,6 +111,12 @@
>  #define NVQUIRK_DIS_CARD_CLK_CONFIG_TAP			BIT(8)
>  #define NVQUIRK_CQHCI_DCMD_R1B_CMD_TIMING		BIT(9)
>  
> +/*
> + * NVQUIRK_HAS_TMCLK is for SoC's having separate timeout clock for Tegra
> + * SDMMC hardware data timeout.
> + */
> +#define NVQUIRK_HAS_TMCLK				BIT(10)
> +
>  /* SDMMC CQE Base Address for Tegra Host Ver 4.1 and Higher */
>  #define SDHCI_TEGRA_CQE_BASE_ADDR			0xF000
>  
> @@ -140,6 +147,7 @@ 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;
> @@ -1433,7 +1441,8 @@ static const struct sdhci_tegra_soc_data soc_data_tegra210 = {
>  		    NVQUIRK_HAS_PADCALIB |
>  		    NVQUIRK_DIS_CARD_CLK_CONFIG_TAP |
>  		    NVQUIRK_ENABLE_SDR50 |
> -		    NVQUIRK_ENABLE_SDR104,
> +		    NVQUIRK_ENABLE_SDR104 |
> +		    NVQUIRK_HAS_TMCLK,
>  	.min_tap_delay = 106,
>  	.max_tap_delay = 185,
>  };
> @@ -1471,6 +1480,7 @@ static const struct sdhci_tegra_soc_data soc_data_tegra186 = {
>  		    NVQUIRK_DIS_CARD_CLK_CONFIG_TAP |
>  		    NVQUIRK_ENABLE_SDR50 |
>  		    NVQUIRK_ENABLE_SDR104 |
> +		    NVQUIRK_HAS_TMCLK |
>  		    NVQUIRK_CQHCI_DCMD_R1B_CMD_TIMING,
>  	.min_tap_delay = 84,
>  	.max_tap_delay = 136,
> @@ -1483,7 +1493,8 @@ static const struct sdhci_tegra_soc_data soc_data_tegra194 = {
>  		    NVQUIRK_HAS_PADCALIB |
>  		    NVQUIRK_DIS_CARD_CLK_CONFIG_TAP |
>  		    NVQUIRK_ENABLE_SDR50 |
> -		    NVQUIRK_ENABLE_SDR104,
> +		    NVQUIRK_ENABLE_SDR104 |
> +		    NVQUIRK_HAS_TMCLK,
>  	.min_tap_delay = 96,
>  	.max_tap_delay = 139,
>  };
> @@ -1611,15 +1622,76 @@ static int sdhci_tegra_probe(struct platform_device *pdev)
>  		goto err_power_req;
>  	}
>  
> -	clk = devm_clk_get(mmc_dev(host->mmc), NULL);
> -	if (IS_ERR(clk)) {
> -		rc = PTR_ERR(clk);
> +	/*
> +	 * Tegra210 and later has separate SDMMC_LEGACY_TM clock used for
> +	 * hardware data 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 separate TMCLK.
> +	 *
> +	 * Old device tree has single sdhci clock. So with addition of TMCLK,
> +	 * retrieving sdhci clock by "sdhci" clock name based on number of
> +	 * clocks in sdhci device node.
> +	 */
> +
> +	if (of_clk_get_parent_count(pdev->dev.of_node) == 1) {
> +		if (soc_data->nvquirks & NVQUIRK_HAS_TMCLK)
> +			dev_warn(&pdev->dev,
> +				 "missing tmclk in the device tree\n");
> +
> +		clk = devm_clk_get(&pdev->dev, NULL);
> +		if (IS_ERR(clk)) {
> +			rc = PTR_ERR(clk);
>  
> -		if (rc != -EPROBE_DEFER)
> -			dev_err(&pdev->dev, "failed to get clock: %d\n", rc);
> +			if (rc != -EPROBE_DEFER)
> +				dev_err(&pdev->dev,
> +					"failed to get sdhci clock: %d\n", rc);
>  
> -		goto err_clk_get;
> +			goto err_power_req;
> +		}
> +	} else {
> +		if (soc_data->nvquirks & NVQUIRK_HAS_TMCLK) {


I think that I would do the inverse of this ...

   } else {
        if (!(soc_data->nvquirks & NVQUIRK_HAS_TMCLK)) {
                dev_err(&pdev->dev, "Device has unexpected clocks!\n");
                rc = -EINVAL;
                goto_power_req;
        }

        clk = devm_clk_get(&pdev->dev, "tmclk");
        ...

If the device does not have a single clock, then we expect it to support
the tmclk. If this is not the case, then this is a bug.

Cheers
Jon

-- 
nvpublic