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Subject: Re: [PATCH V7 1/2] scsi: ufs: set the device reference clock setting
To:     Evan Green <evgreen@chromium.org>
Cc:     subhashj@codeaurora.org, cang@codeaurora.org,
        vivek.gautam@codeaurora.org,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Vinayak Holikatti <vinholikatti@gmail.com>,
        jejb@linux.vnet.ibm.com, martin.petersen@oracle.com,
        asutoshd@codeaurora.org, riteshh@codeaurora.org,
        adrian.hunter@intel.com, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1533113338-31750-1-git-send-email-sayalil@codeaurora.org>
 <1533113338-31750-2-git-send-email-sayalil@codeaurora.org>
 <CAE=gft6H2iYx59fXc2SHP+Rr9M07Vjk99-Rgk1Kx-GnVJT86DQ@mail.gmail.com>
From:   Sayali Lokhande <sayalil@codeaurora.org>
Message-ID: <fa0578ee-57ac-923c-8c20-8b2b5fa13829@codeaurora.org>
Date:   Thu, 9 Aug 2018 14:20:25 +0530
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Hi Evan,

On 8/6/2018 10:56 PM, Evan Green wrote:
> Hi Sayali,
>
> On Wed, Aug 1, 2018 at 1:49 AM Sayali Lokhande <sayalil@codeaurora.org> wrote:
>> From: Subhash Jadavani <subhashj@codeaurora.org>
>>
>> UFS host supplies the reference clock to UFS device and UFS device
>> specification allows host to provide one of the 4 frequencies (19.2 MHz,
>> 26 MHz, 38.4 MHz, 52 MHz) for reference clock. Host should set the
>> device reference clock frequency setting in the device based on what
>> frequency it is supplying to UFS device.
>>
>> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
>> ---
>>   drivers/scsi/ufs/ufs.h           |  8 ++++
>>   drivers/scsi/ufs/ufshcd-pltfrm.c |  2 +
>>   drivers/scsi/ufs/ufshcd.c        | 84 ++++++++++++++++++++++++++++++++++++++++
>>   drivers/scsi/ufs/ufshcd.h        |  2 +
>>   4 files changed, 96 insertions(+)
>>
>> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h
>> index 14e5bf7..89e0a33 100644
>> --- a/drivers/scsi/ufs/ufs.h
>> +++ b/drivers/scsi/ufs/ufs.h
>> @@ -378,6 +378,14 @@ enum query_opcode {
>>          UPIU_QUERY_OPCODE_TOGGLE_FLAG   = 0x8,
>>   };
>>
>> +/* bRefClkFreq attribute values */
>> +enum ref_clk_freq {
>> +       REF_CLK_FREQ_19_2_MHZ   = 19200000,
>> +       REF_CLK_FREQ_26_MHZ     = 26000000,
>> +       REF_CLK_FREQ_38_4_MHZ   = 38400000,
>> +       REF_CLK_FREQ_52_MHZ     = 52000000,
>> +};
>> +
>>   /* Query response result code */
>>   enum {
>>          QUERY_RESULT_SUCCESS                    = 0x00,
>> diff --git a/drivers/scsi/ufs/ufshcd-pltfrm.c b/drivers/scsi/ufs/ufshcd-pltfrm.c
>> index e82bde0..0953563 100644
>> --- a/drivers/scsi/ufs/ufshcd-pltfrm.c
>> +++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
>> @@ -343,6 +343,8 @@ int ufshcd_pltfrm_init(struct platform_device *pdev,
>>          pm_runtime_set_active(&pdev->dev);
>>          pm_runtime_enable(&pdev->dev);
>>
>> +       ufshcd_parse_dev_ref_clk_freq(hba);
>> +
>>          ufshcd_init_lanes_per_dir(hba);
>>
>>          err = ufshcd_init(hba, mmio_base, irq);
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index c5b1bf1..619313b 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -6296,6 +6296,84 @@ static void ufshcd_def_desc_sizes(struct ufs_hba *hba)
>>          hba->desc_size.hlth_desc = QUERY_DESC_HEALTH_DEF_SIZE;
>>   }
>>
>> +void ufshcd_parse_dev_ref_clk_freq(struct ufs_hba *hba)
>> +{
>> +       struct device *dev = hba->dev;
>> +       struct device_node *np = dev->of_node;
>> +       struct clk *refclk = NULL;
>> +
>> +       if (!np)
>> +               return;
>> +
>> +       refclk = of_clk_get_by_name(np, "ref_clk");
>> +       if (refclk)
>> +               hba->dev_ref_clk_freq  = clk_get_rate(refclk);
>> +       else if (!refclk ||
>> +               (hba->dev_ref_clk_freq > REF_CLK_FREQ_52_MHZ)) {
> What is this logic? The !refclk condition will always be true since
> you're in the else case of if (refclk). Also, even if the second part
> were executed somehow, you haven't assigned dev_ref_clk_freq yet, so
> how can its value be anything other than 0? Maybe that whole
> conditional was just not supposed to be an "else" at all, but a
> standalone if?
Agree. Will update.
>> +               dev_err(hba->dev,
>> +               "%s: invalid ref_clk setting = %u\n",
>> +               __func__, hba->dev_ref_clk_freq);
> There's probably no need to complain if the clock simply couldn't be
> found, only if an unexpected value was found.
Agree. Will update.
>> +               hba->dev_ref_clk_freq = 0;
>> +       }
>> +}
>> +
>> +static int ufshcd_set_dev_ref_clk(struct ufs_hba *hba)
>> +{
>> +       int err = 0;
>> +       int ref_clk = -1;
>> +       static const char * const ref_clk_freqs[] = {"19.2 MHz", "26 MHz",
>> +                                                    "38.4 MHz", "52 MHz"};
>> +
>> +       err = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_READ_ATTR,
>> +                       QUERY_ATTR_IDN_REF_CLK_FREQ, 0, 0, &ref_clk);
>> +
>> +       if (err) {
>> +               dev_err(hba->dev, "%s: failed reading bRefClkFreq. err = %d\n",
>> +                        __func__, err);
>> +               goto out;
>> +       }
>> +
>> +       switch (hba->dev_ref_clk_freq) {
>> +       case REF_CLK_FREQ_19_2_MHZ:
>> +               hba->dev_ref_clk_freq = 0x0;
>> +               break;
>> +       case REF_CLK_FREQ_26_MHZ:
>> +               hba->dev_ref_clk_freq = 0x1;
>> +               break;
>> +       case REF_CLK_FREQ_38_4_MHZ:
>> +               hba->dev_ref_clk_freq = 0x2;
>> +               break;
>> +       case REF_CLK_FREQ_52_MHZ:
>> +               hba->dev_ref_clk_freq = 0x3;
>> +               break;
>> +       default:
>> +               dev_err(hba->dev,
>> +               "%s: invalid ref_clk setting = %u\n",
>> +               __func__, hba->dev_ref_clk_freq);
>> +               goto out;
>> +       }
> Please don't assign two different things (frequency in Hertz and
> bref_clk value) into the same structure member.
>
> I think rather than having this switch statement you should iterate
> through a table that contains elements of {freq_hz, bref_clk, string}.
> I think you should do this up in ufshcd_parse_dev_ref_clk_freq so that
> you don't have to redo that calculation on every rescan. Then store
> the final bRefClkFreq value (or -1 if no definitive answer could be
> reached) in your new structure member. Then all this function does is
> 1) Nothing if dev_ref_clk_freq is -1, or 2) read and maybe write the
> attribute.
Agree. Will update.
>> +
>> +       if (ref_clk == hba->dev_ref_clk_freq)
>> +               goto out; /* nothing to update */
>> +
>> +       err = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_WRITE_ATTR,
>> +                       QUERY_ATTR_IDN_REF_CLK_FREQ, 0, 0,
>> +                       &hba->dev_ref_clk_freq);
>> +
>> +       if (err)
>> +               dev_err(hba->dev, "%s: bRefClkFreq setting to %s failed\n",
>> +                       __func__, ref_clk_freqs[hba->dev_ref_clk_freq]);
>> +       /*
>> +        * It is good to print this out here to debug any later failures
>> +        * related to gear switch.
>> +        */
>> +       dev_dbg(hba->dev, "%s: bRefClkFreq setting to %s succeeded\n",
>> +                       __func__, ref_clk_freqs[hba->dev_ref_clk_freq]);
>> +
>> +out:
>> +       return err;
>> +}
>> +
>>   /**
>>    * ufshcd_probe_hba - probe hba to detect device and initialize
>>    * @hba: per-adapter instance
>> @@ -6361,6 +6439,12 @@ static int ufshcd_probe_hba(struct ufs_hba *hba)
>>                          "%s: Failed getting max supported power mode\n",
>>                          __func__);
>>          } else {
>> +               /*
>> +                * Set the right value to bRefClkFreq before attempting to
>> +                * switch to HS gears.
>> +                */
>> +               if (hba->dev_ref_clk_freq)
>> +                       ufshcd_set_dev_ref_clk(hba);
>>                  ret = ufshcd_config_pwr_mode(hba, &hba->max_pwr_info.info);
>>                  if (ret) {
>>                          dev_err(hba->dev, "%s: Failed setting power mode, err = %d\n",
>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>> index 8110dcd..101a75c 100644
>> --- a/drivers/scsi/ufs/ufshcd.h
>> +++ b/drivers/scsi/ufs/ufshcd.h
>> @@ -548,6 +548,7 @@ struct ufs_hba {
>>          void *priv;
>>          unsigned int irq;
>>          bool is_irq_enabled;
>> +       u32 dev_ref_clk_freq;
> If you followed my suggestion of this storing _only_ the bRefClkFreq
> value or -1 if unset, then this would need to be signed, and
> initialized somewhere so that 0 wasn't accidentally taken to be a
> parsed value.
Will check and update (if necessary).
>>          /* Interrupt aggregation support is broken */
>>          #define UFSHCD_QUIRK_BROKEN_INTR_AGGR                   0x1
>> @@ -746,6 +747,7 @@ static inline void ufshcd_rmwl(struct ufs_hba *hba, u32 mask, u32 val, u32 reg)
>>   int ufshcd_wait_for_register(struct ufs_hba *hba, u32 reg, u32 mask,
>>                                  u32 val, unsigned long interval_us,
>>                                  unsigned long timeout_ms, bool can_sleep);
>> +void ufshcd_parse_dev_ref_clk_freq(struct ufs_hba *hba);
>>
>>   static inline void check_upiu_size(void)
>>   {
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>