Re: [PATCH V2 2/2] mmc: sdhci-msm: Re-initialize DLL if MCLK is gated dynamically

Veerabhadrarao Badiganti
2018-10-23T12:13:34Z

On 10/17/2018 3:58 AM, Evan Green wrote:
> On Mon, Oct 8, 2018 at 6:26 AM Veerabhadrarao Badiganti
> <vbadigan@codeaurora.org> wrote:
>> On few SDHCI-MSM controllers, the host controller's clock tuning
>> circuit may go out of sync if controller clocks are gated which
>> eventually will result in data CRC, command CRC/timeout errors.
>> To overcome this h/w limitation, the DLL needs to be re-initialized
>> and restored with its old settings once clocks are ungated.
>>
>> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
>> ---
>> drivers/mmc/host/sdhci-msm.c | 67 ++++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 65 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
>> index 6918e70..1eb70c0 100644
>> --- a/drivers/mmc/host/sdhci-msm.c
>> +++ b/drivers/mmc/host/sdhci-msm.c
>> @@ -234,6 +234,7 @@ struct sdhci_msm_variant_ops {
>> */
>> struct sdhci_msm_variant_info {
>> bool mci_removed;
>> + bool uses_sdcdc10;
> What does that flag mean? Couldn't this just be called something like
> restore_dll_config?

'sdcdc10' is the DLL code-name that is being used in SDHC controller on
SDM845.
I should have named it as uses_sdcdc10_dll.
I will update the name to be more meaningful.

>
>> const struct sdhci_msm_variant_ops *var_ops;
>> const struct sdhci_msm_offset *offset;
>> };
>> @@ -264,6 +265,8 @@ struct sdhci_msm_host {
>> u32 vmmc_level[2];
>> bool vqmmc_load;
>> u32 vqmmc_level[2];
>> + bool uses_sdcdc10_dll;
>> + bool restore_sdr_dll_cfg;
> restore_sdr_dll_cfg appears to not be used.

Yes, this needs to be removed, will remove it. Thanks for pointing.

>> };
>>
>> static const struct sdhci_msm_offset *sdhci_priv_msm_offset(struct sdhci_host *host)
>> @@ -1031,6 +1034,36 @@ static int sdhci_msm_hs400_dll_calibration(struct sdhci_host *host)
>> return ret;
>> }
>>
>> +static int sdhci_msm_restore_sdr_dll_config(struct sdhci_host *host)
>> +{
>> + struct mmc_ios ios = host->mmc->ios;
>> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> + struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>> + int ret;
>> +
>> + /*
>> + * SDR DLL comes into picure only if clock frequency is greater than
>> + * 100MHz. And its needed only for SDR104, HS200 and HS400 cards.
>> + * Its not needed for HS400es cards.
>> + */
>> + if (host->clock <= CORE_FREQ_100MHZ ||
>> + !(ios.timing == MMC_TIMING_MMC_HS400 ||
>> + ios.timing == MMC_TIMING_MMC_HS200 ||
>> + ios.timing == MMC_TIMING_UHS_SDR104) ||
>> + ios.enhanced_strobe)
>> + return 0;
>> +
>> + /* Reset the tuning block */
>> + ret = msm_init_cm_dll(host);
> Is this reinit required? It's kind of meaty.

DLL re-initialization is very-much needed.
Its as per DLL h/w team instructions to support sdcdc10 DLL (10nm DLL)

>> + if (ret)
>> + return ret;
>> +
>> + /* Restore the tuning block */
>> + ret = msm_config_cm_dll_phase(host, msm_host->saved_tuning_phase);
>> +
>> + return ret;
>> +}
>> +
>> static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
>> {
>> struct sdhci_host *host = mmc_priv(mmc);
>> @@ -1075,7 +1108,6 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
>> if (rc)
>> return rc;
>>
>> - msm_host->saved_tuning_phase = phase;
>> rc = mmc_send_tuning(mmc, opcode, NULL);
>> if (!rc) {
>> /* Tuning is successful at this tuning point */
>> @@ -1100,6 +1132,7 @@ static int sdhci_msm_execute_tuning(struct mmc_host *mmc, u32 opcode)
>> rc = msm_config_cm_dll_phase(host, phase);
>> if (rc)
>> return rc;
>> + msm_host->saved_tuning_phase = phase;
>> dev_dbg(mmc_dev(mmc), "%s: Setting the tuning phase to %d\n",
>> mmc_hostname(mmc), phase);
>> } else {
>> @@ -1807,19 +1840,39 @@ static int sdhci_msm_start_signal_voltage_switch(struct mmc_host *mmc,
>>
>> static const struct sdhci_msm_variant_info sdhci_msm_mci_var = {
>> .mci_removed = false,
>> + .uses_sdcdc10 = false,
>> + .var_ops = &mci_var_ops,
>> + .offset = &sdhci_msm_mci_offset,
>> +};
>> +
>> +static const struct sdhci_msm_variant_info sdhci_msm_mci_sdcdc10_var = {
>> + .mci_removed = false,
>> + .uses_sdcdc10 = true,
>> .var_ops = &mci_var_ops,
>> .offset = &sdhci_msm_mci_offset,
>> };
>>
>> static const struct sdhci_msm_variant_info sdhci_msm_v5_var = {
>> .mci_removed = true,
>> + .uses_sdcdc10 = false,
>> + .var_ops = &v5_var_ops,
>> + .offset = &sdhci_msm_v5_offset,
>> +};
>> +
>> +static const struct sdhci_msm_variant_info sdhci_msm_v5_sdcdc10_var = {
>> + .mci_removed = true,
>> + .uses_sdcdc10 = true,
>> .var_ops = &v5_var_ops,
>> .offset = &sdhci_msm_v5_offset,
>> };
>>
>> static const struct of_device_id sdhci_msm_dt_match[] = {
>> {.compatible = "qcom,sdhci-msm-v4", .data = &sdhci_msm_mci_var},
>> + {.compatible = "qcom,sdhci-msm-v4-sdcdc10",
>> + .data = &sdhci_msm_mci_sdcdc10_var},
>> {.compatible = "qcom,sdhci-msm-v5", .data = &sdhci_msm_v5_var},
>> + {.compatible = "qcom,sdhci-msm-v5-sdcdc10",
>> + .data = &sdhci_msm_v5_sdcdc10_var},
>> {},
>> };
>>
>> @@ -1880,6 +1933,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>> var_info = of_device_get_match_data(&pdev->dev);
>>
>> msm_host->mci_removed = var_info->mci_removed;
>> + msm_host->uses_sdcdc10_dll = var_info->uses_sdcdc10;
>> msm_host->var_ops = var_info->var_ops;
>> msm_host->offset = var_info->offset;
>>
>> @@ -2124,9 +2178,18 @@ static int sdhci_msm_runtime_resume(struct device *dev)
>> struct sdhci_host *host = dev_get_drvdata(dev);
>> struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>> + int ret;
>>
>> - return clk_bulk_prepare_enable(ARRAY_SIZE(msm_host->bulk_clks),
>> + ret = clk_bulk_prepare_enable(ARRAY_SIZE(msm_host->bulk_clks),
>> msm_host->bulk_clks);
> It might be nicer to just put an if (ret) return ret; here, instead of
> rolling it into the next conditional.

Sure. Will update it.

>
>> + /*
>> + * Whenever core-clock is gated dynamically, it's needed to
>> + * restore the SDR DLL settings when the clock is ungated.
>> + */
>> + if (!ret && msm_host->uses_sdcdc10_dll && msm_host->clk_rate)
>> + ret = sdhci_msm_restore_sdr_dll_config(host);
>> +
>> + return ret;
>> }
>> #endif
>>
>> --
>> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
>>