RE: [PATCH V1 1/3] scsi: ufs: set the device reference clock setting

sayali
2018-06-01T13:34:48Z

-----Original Message-----
From: Adrian Hunter [mailto:adrian.hunter@intel.com]
Sent: Friday, June 01, 2018 6:48 PM
To: sayali <sayalil@codeaurora.org>; subhashj@codeaurora.org; cang@codeaurora.org; vivek.gautam@codeaurora.org; rnayak@codeaurora.org; vinholikatti@gmail.com; jejb@linux.vnet.ibm.com; martin.petersen@oracle.com; asutoshd@codeaurora.org; evgreen@chromium.org
Cc: linux-scsi@vger.kernel.org; 'open list' <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V1 1/3] scsi: ufs: set the device reference clock setting

On 01/06/18 16:11, sayali wrote:
> Hi Adrain,
>
> Updated my comments inline. Please check.
>
> Thanks,
> Sayali
> -----Original Message-----
> From: Adrian Hunter [mailto:adrian.hunter@intel.com]
> Sent: Friday, June 01, 2018 5:59 PM
> To: Sayali Lokhande <sayalil@codeaurora.org>; subhashj@codeaurora.org;
> cang@codeaurora.org; vivek.gautam@codeaurora.org;
> rnayak@codeaurora.org; vinholikatti@gmail.com;
> jejb@linux.vnet.ibm.com; martin.petersen@oracle.com;
> asutoshd@codeaurora.org; evgreen@chromium.org
> Cc: linux-scsi@vger.kernel.org; open list
> <linux-kernel@vger.kernel.org>
> Subject: Re: [PATCH V1 1/3] scsi: ufs: set the device reference clock
> setting
>
> On 01/06/18 13:42, Sayali Lokhande 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>
>> [cang@codeaurora.org: Resolved trivial merge conflicts]
>> Signed-off-by: Can Guo <cang@codeaurora.org>
>> Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
>> ---
>> drivers/scsi/ufs/ufs.h | 9 +++++++
>> drivers/scsi/ufs/ufshcd.c | 62
>> +++++++++++++++++++++++++++++++++++++++++++++++
>> drivers/scsi/ufs/ufshcd.h | 1 +
>> 3 files changed, 72 insertions(+)
>>
>> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h index
>> 14e5bf7..e15deb0 100644
>> --- a/drivers/scsi/ufs/ufs.h
>> +++ b/drivers/scsi/ufs/ufs.h
>> @@ -378,6 +378,15 @@ enum query_opcode {
>> UPIU_QUERY_OPCODE_TOGGLE_FLAG = 0x8,
>> };
>>
>> +/* bRefClkFreq attribute values */
>> +enum ref_clk_freq {
>> + REF_CLK_FREQ_19_2_MHZ = 0x0,
>> + REF_CLK_FREQ_26_MHZ = 0x1,
>> + REF_CLK_FREQ_38_4_MHZ = 0x2,
>> + REF_CLK_FREQ_52_MHZ = 0x3,
>> + REF_CLK_FREQ_MAX = REF_CLK_FREQ_52_MHZ,
>> +};
>> +
>> /* Query response result code */
>> enum {
>> QUERY_RESULT_SUCCESS = 0x00,
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index c5b1bf1..3669bc4 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -6297,6 +6297,63 @@ static void ufshcd_def_desc_sizes(struct
>> ufs_hba *hba) }
>>
>> /**
>> + * ufshcd_set_dev_ref_clk - set the device bRefClkFreq
>> + * @hba: per-adapter instance
>> + * @ref_clk_freq: refrerence clock frequency to be set
>> + *
>> + * Read the current value of the bRefClkFreq attribute from device
>> +and update it
>> + * if host is supplying different reference clock frequency than one
>> +mentioned
>> + * in bRefClkFreq attribute.
>> + *
>> + * Returns zero on success, non-zero error value on failure.
>> + */
>> +static int ufshcd_set_dev_ref_clk(struct ufs_hba *hba, u32
>> +ref_clk_freq) {
>> + int err = 0;
>> + int ref_clk = -1;
>> + static const char * const ref_clk_freqs[] = {"19.2 MHz", "26 MHz",
>> + "38.4 MHz", "52 MHz"};
>> +
>> + hba->dev_ref_clk_freq = ref_clk_freq;
>> + 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 < 0) || (ref_clk > REF_CLK_FREQ_52_MHZ)) {
>
> If you used u32 ref_clk then you wouldn't have to check < 0, also you should use REF_CLK_FREQ_MAX not REF_CLK_FREQ_52_MHZ, but really why is this check needed anyway?
> [Sayali] Here ref_clk is defined as integer with value -1. We are then reading bRefClkFreq attribute from device into ref_clk and hence the sanity check is required before we update/write bRefClkFreq attribute.

But why sanity check a value that is going to be overwritten?
[Sayali] Agreed. I need not check the ref_clk(which is the current setting), but still I should add check for new setting " ref_clk_freq" that is passed and going to be written (like ref_clk_freq < REF_CLK_FREQ_MAX). Will update in next patchset.

>
>> + dev_err(hba->dev, "%s: invalid ref_clk setting = %d\n",
>> + __func__, ref_clk);
>> + err = -EINVAL;
>> + 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);
>> +
>> + if (err)
>> + dev_err(hba->dev, "%s: bRefClkFreq setting to %s failed\n",
>> + __func__, ref_clk_freqs[hba->dev_ref_clk_freq]);
>> + else
>> + /*
>> + * It is good to print this out here to debug any later failures
>> + * related to gear switch.
>> + */
>> + dev_info(hba->dev, "%s: bRefClkFreq setting to %s succeeded\n",
>> + __func__, ref_clk_freqs[hba->dev_ref_clk_freq]);
>
> Why not make this dev_dbg and print always even when there is no update.
> [Sayali] Agreed. Will update in next patchsets.
>
>> +
>> +out:
>> + return err;
>> +}
>> +
>> +/**
>> * ufshcd_probe_hba - probe hba to detect device and initialize
>> * @hba: per-adapter instance
>> *
>> @@ -6361,6 +6418,11 @@ 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.
>> + */
>> + ufshcd_set_dev_ref_clk(hba, REF_CLK_FREQ_19_2_MHZ);
>> 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..b026ad8 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;
>>
>> /* Interrupt aggregation support is broken */
>> #define UFSHCD_QUIRK_BROKEN_INTR_AGGR 0x1
>>
>
>
>