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Date:   Tue, 21 Aug 2018 15:08:54 +0530
From:   Sayali Lokhande <sayalil@...eaurora.org>
To:     Evan Green <evgreen@...omium.org>
Cc:     subhashj@...eaurora.org, cang@...eaurora.org,
        vivek.gautam@...eaurora.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Vinayak Holikatti <vinholikatti@...il.com>,
        jejb@...ux.vnet.ibm.com, martin.petersen@...cle.com,
        asutoshd@...eaurora.org, riteshh@...eaurora.org,
        adrian.hunter@...el.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 1/2] scsi: ufs: set the device reference clock setting

Hi Evan,

On 8/17/2018 10:57 PM, Evan Green wrote:
> On Thu, Aug 9, 2018 at 2:10 AM Sayali Lokhande <sayalil@...eaurora.org> wrote:
>> From: Subhash Jadavani <subhashj@...eaurora.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@...eaurora.org>
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> Signed-off-by: Sayali Lokhande <sayalil@...eaurora.org>
>> ---
>>   drivers/scsi/ufs/ufs.h           | 21 ++++++++++
>>   drivers/scsi/ufs/ufshcd-pltfrm.c |  2 +
>>   drivers/scsi/ufs/ufshcd.c        | 89 ++++++++++++++++++++++++++++++++++++++++
>>   drivers/scsi/ufs/ufshcd.h        |  2 +
>>   4 files changed, 114 insertions(+)
>>
>> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h
>> index 14e5bf7..c555ac0 100644
>> --- a/drivers/scsi/ufs/ufs.h
>> +++ b/drivers/scsi/ufs/ufs.h
>> @@ -378,6 +378,27 @@ enum query_opcode {
>>          UPIU_QUERY_OPCODE_TOGGLE_FLAG   = 0x8,
>>   };
>>
>> +/* bRefClkFreq attribute values */
>> +enum ref_clk_freq_hz {
>> +       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,
>> +};
>> +
>> +enum bref_clk_freq {
>> +       bREF_CLK_FREQ_0, /* 19.2 MHz */
>> +       bREF_CLK_FREQ_1, /* 26 MHz */
>> +       bREF_CLK_FREQ_2, /* 38.4 MHz */
>> +       bREF_CLK_FREQ_3, /* 52 MHz */
>> +       bREF_CLK_FREQ_INVAL,
>> +};
> These enums are not helpful, roughly the equivalent of VALUE_1000 =
> 1000. Replace both with a single one, something like:
>
> enum ufs_ref_clk_freq {
>          UFS_REF_CLK_19P2MHZ = 0,
>          UFS_REF_CLK_26MHZ = 1,
>          UFS_REF_CLK_38P4MHZ = 2,
>          UFS_REF_CLK_52MHZ = 3,
>          UFS_REF_CLK_INVAL = -1
> };
Agreed. Will update.
>> +
>> +struct ufs_ref_clk {
>> +       enum ref_clk_freq_hz freq_hz;
> Just make this an unsigned, no need for an enum of identity values.
Done.
>> +       enum bref_clk_freq val;
>> +};
>> +
>>   /* 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..0cbdde7 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -6296,6 +6296,89 @@ static void ufshcd_def_desc_sizes(struct ufs_hba *hba)
>>          hba->desc_size.hlth_desc = QUERY_DESC_HEALTH_DEF_SIZE;
>>   }
>>
>> +static struct ufs_ref_clk ufs_ref_clk_freqs[] = {
>> +       {REF_CLK_FREQ_19_2_MHZ, bREF_CLK_FREQ_0},
> Then these should just be something like:
>          {19200000, UFS_REF_CLK_19P2MHZ},
>          ...
>          {0, UFS_REF_CLK_INVAL},
Done.
>> +       {REF_CLK_FREQ_26_MHZ, bREF_CLK_FREQ_1},
>> +       {REF_CLK_FREQ_38_4_MHZ, bREF_CLK_FREQ_2},
>> +       {REF_CLK_FREQ_52_MHZ, bREF_CLK_FREQ_3},
>> +};
>> +
>> +static inline enum bref_clk_freq
>> +ufs_get_bref_clk_for_ref_clk_freq_hz(u32 freq)
>> +{
>> +       enum bref_clk_freq val;
>> +
>> +       for (val = bREF_CLK_FREQ_0; val <= bREF_CLK_FREQ_3; val++)
> In my suggestion above, I terminated the table with {0,
> UFS_REF_CLK_INVAL}. Then you could change this to a while loop that
> stops when you see that sentinel node. I don't like the way it is now
> because 1) You're making assumptions about the enum values being equal
> to array indices, which may not line up if the next UFS spec adds
> values that aren't contiguous (and defeats the whole point of the
> table), and 2) Using <= LAST_VALID_VALUE makes this susceptible to
> bugs when more valid values are added but someone forgets to go find
> this loop and update it.
Agreed. Will update.
>> +               if (ufs_ref_clk_freqs[val].freq_hz == freq)
>> +                       return val;
>> +
>> +       /* if no match found, return invalid*/
>> +       return bREF_CLK_FREQ_INVAL;
>> +}
>> +
>> +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;
>> +       u32 freq = 0;
>> +
>> +       if (!np)
>> +               return;
>> +
>> +       hba->dev_ref_clk_freq = bREF_CLK_FREQ_INVAL;
>> +
>> +       refclk = of_clk_get_by_name(np, "ref_clk");
>> +       if (!refclk)
>> +               return;
>> +
>> +       freq = clk_get_rate(refclk);
>> +       if (freq > REF_CLK_FREQ_52_MHZ) {
>> +               dev_err(hba->dev,
>> +               "%s: invalid ref_clk setting = %d\n",
>> +               __func__, freq);
>> +               return;
>> +       }
>> +
>> +       hba->dev_ref_clk_freq =
>> +               ufs_get_bref_clk_for_ref_clk_freq_hz(freq);
>> +}
>> +
>> +static int ufshcd_set_dev_ref_clk(struct ufs_hba *hba)
>> +{
>> +       int err = 0;
>> +       int ref_clk = -1;
>> +
>> +       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;
>> +       }
>> +
>> +       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);
> This is probably a nit, but I think the compiler is allowed to choose
> any type for your enum that fits all of its values. This may not be a
> u32, so you should probably create a u32 local, and assign into it
> before passing a pointer into this function.
>
> Ah wait, I see that you made the member a u32. It might be nicer to
> type the member as the enum, and then do this local conversion as I've
> mentioned. That will allow the compiler to help check more.
Agree. Will update.
>> +
>> +       if (err)
>> +               dev_err(hba->dev, "%s: bRefClkFreq setting to %d Hz failed\n",
>> +               __func__, ufs_ref_clk_freqs[hba->dev_ref_clk_freq].freq_hz);
>> +       /*
>> +        * 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 %d Hz succeeded\n",
>> +               __func__, ufs_ref_clk_freqs[hba->dev_ref_clk_freq].freq_hz);
>> +
>> +out:
>> +       return err;
>> +}
>> +
>>   /**
>>    * ufshcd_probe_hba - probe hba to detect device and initialize
>>    * @hba: per-adapter instance
>> @@ -6361,6 +6444,12 @@ 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 < bREF_CLK_FREQ_INVAL)
>> +                       ufshcd_set_dev_ref_clk(hba);
> As mentioned by other reviewers, you're calling this function, but you
> haven't called ufshcd_parse_dev_ref_clk_freq in all cases that lead to
> this. So this function is now setting 19.2MHz into a whole set of
> devices who haven't specified it. Perhaps the initialization of the
> member needs to go in ufshcd_alloc_host. (Look for callers of that to
> find other paths that circumvent your parse function). I'm not sure
> how to advise on enabling this functionality for non-DT machines.
Agreed. Will add the parse function in ufshcd_alloc_host() itself (so 
that it can be called/initialised always).
For non-DT users, even I am unsure.  In current implementation, this 
will just set ref_clk as invalid and bail out(no update) for non-DT users.
>>                  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;
> As I mentioned above, this might be better as the enum type.
Done.
>>          /* 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);
> I wonder if this should fail if you end up finding a DT property, but
> it's a crazy invalid value. What do you think?
For any weird/invalid value ia parsed (from DT), we wont actually update 
the ref_clk in device and just bail out based on REF_CLK_INVAL check.
>>   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
>>

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