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

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On 10/17/2018 3:58 AM, Evan Green wrote:
On Mon, Oct 8, 2018 at 6:26 AM Veerabhadrarao Badiganti
<vbadigan@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
---
  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.





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