Re: [PATCH v6 7/7] sdhci: tegra: Add missing TMCLK for data timeout

[Jon Hunter]

On 27/08/2020 16:43, Sowjanya Komatineni wrote:
> 
> On 8/27/20 8:14 AM, Jon Hunter wrote:
>> On 27/08/2020 16:03, Sowjanya Komatineni wrote:
>>> On 8/27/20 1:40 AM, Jon Hunter wrote:
>>>> 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@xxxxxxxxxxxxxxx> # 5.4
>>>>> Tested-by: Jon Hunter <jonathanh@xxxxxxxxxx>
>>>>> Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>
>>>>> Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
>>>>> ---
>>>>>    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
>>> I don't see other drivers validating for unexpected device tree entries.
>>>
>>> Also only for SoC with quirk HAS_TMCLK, we are retrieving TMCLK with
>>> clock name and enabling it.
>>>
>>> So for other SoC even if device tree has additional clock entry other
>>> than sdhci driver don't use it and also dt-binding do not have any tmclk
>>> entry for other SoC. So why would this be a bug?
>> In the device tree binding doc, we say has two clocks for Tegra210,
>> Tegra186 and Tegra194 and one clock for all other devices. So if we no
>> there is more than 1 but the device does not have this quirk, then the
>> device-tree does not reflect what is stated in the binding doc or the
>> quirk is no populated as it should be. I feel that either case is a bug.
>>
>> Now of course it could be possible for someone to add a 3rd clock for
>> Tegra210 and we would not detect this but like you said we don't check
>> all conditions. So yes we don't catch all cases, but the ones that
>> matter.
>>
>> Jon
>>
> Based on internal discussion with Thierry we don't need to handle clocks
> 
> order in driver. So will revert clock retrieval to same as in v4 and
> will send v7 series.

Yes OK fine. Maybe I am being too overly cautious as usual!

Jon

-- 
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