Re: [PATCH v5 6/8] scsi: ufs: Add dev ref clock gating wait time support

Stanley Chu
2020-02-05T02:50:49Z

Hi Can,

On Mon, 2020-02-03 at 01:17 -0800, Can Guo wrote:
> In UFS version 3.0, a newly added attribute bRefClkGatingWaitTime defines
> the minimum time for which the reference clock is required by device during
> transition to LS-MODE or HIBERN8 state. Make this change to reflect the new
> requirement by adding delays before turning off the clock.
>
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
> ---
> drivers/scsi/ufs/ufs.h | 3 +++
> drivers/scsi/ufs/ufshcd.c | 40 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 43 insertions(+)
>
> diff --git a/drivers/scsi/ufs/ufs.h b/drivers/scsi/ufs/ufs.h
> index cfe3803..304076e 100644
> --- a/drivers/scsi/ufs/ufs.h
> +++ b/drivers/scsi/ufs/ufs.h
> @@ -167,6 +167,7 @@ enum attr_idn {
> QUERY_ATTR_IDN_FFU_STATUS = 0x14,
> QUERY_ATTR_IDN_PSA_STATE = 0x15,
> QUERY_ATTR_IDN_PSA_DATA_SIZE = 0x16,
> + QUERY_ATTR_IDN_REF_CLK_GATING_WAIT_TIME = 0x17,
> };
>
> /* Descriptor idn for Query requests */
> @@ -534,6 +535,8 @@ struct ufs_dev_info {
> u16 wmanufacturerid;
> /*UFS device Product Name */
> u8 *model;
> + u16 spec_version;
> + u32 clk_gating_wait_us;
> };
>
> /**
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index e8f7f9d..d5c547b 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -91,6 +91,9 @@
> /* default delay of autosuspend: 2000 ms */
> #define RPM_AUTOSUSPEND_DELAY_MS 2000
>
> +/* Default value of wait time before gating device ref clock */
> +#define UFSHCD_REF_CLK_GATING_WAIT_US 0xFF /* microsecs */
> +
> #define ufshcd_toggle_vreg(_dev, _vreg, _on) \
> ({ \
> int _ret; \
> @@ -3281,6 +3284,37 @@ static inline int ufshcd_read_unit_desc_param(struct ufs_hba *hba,
> param_offset, param_read_buf, param_size);
> }
>
> +static int ufshcd_get_ref_clk_gating_wait(struct ufs_hba *hba)
> +{
> + int err = 0;
> + u32 gating_wait = UFSHCD_REF_CLK_GATING_WAIT_US;
> +
> + if (hba->dev_info.spec_version >= 0x300) {
> + err = ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_READ_ATTR,
> + QUERY_ATTR_IDN_REF_CLK_GATING_WAIT_TIME, 0, 0,
> + &gating_wait);
> + if (err)
> + dev_err(hba->dev, "Failed reading bRefClkGatingWait. err = %d, use default %uus\n",
> + err, gating_wait);
> +
> + if (gating_wait == 0) {
> + gating_wait = UFSHCD_REF_CLK_GATING_WAIT_US;
> + dev_err(hba->dev, "Undefined ref clk gating wait time, use default %uus\n",
> + gating_wait);
> + }
> +
> + /*
> + * bRefClkGatingWaitTime defines the minimum time for which the
> + * reference clock is required by device during transition from
> + * HS-MODE to LS-MODE or HIBERN8 state. Give it more time to be
> + * on the safe side.
> + */
> + hba->dev_info.clk_gating_wait_us = gating_wait + 50;

Not sure if the additional 50us wait time here is too large.

Is there any special reason to fix it as "50"?

Thanks,
Stanley

> &dev_info->model, SD_ASCII_STD);
> @@ -7003,6 +7041,8 @@ static int ufshcd_device_params_init(struct ufs_hba *hba)
> goto out;
> }
>
> + ufshcd_get_ref_clk_gating_wait(hba);
> +
> ufs_fixup_device_setup(hba);
>
> if (!ufshcd_query_flag_retry(hba, UPIU_QUERY_OPCODE_READ_FLAG,