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

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Date:   Wed, 5 Aug 2020 17:07:10 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Adrian Hunter <adrian.hunter@...el.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 8/5/20 1:06 AM, Adrian Hunter wrote:
> 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?

Thanks Adrian. Will resend with fixes tag.

Sowjanya

>
>> 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);
>>   
>>