Re: [PATCH v4 5/8] scsi: ufs: core: Enable multi-level gear scaling

["Peter Wang (王信友)" <peter.wang@mediatek.com>]

On Mon, 2025-02-10 at 18:02 +0800, Ziqi Chen wrote:
> 
> External email : Please do not click links or open attachments until
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> 
> 
> From: Can Guo <quic_cang@quicinc.com>
> 
> With OPP V2 enabled, devfreq can scale clocks amongst multiple
> frequency
> plans. However, the gear speed is only toggled between min and max
> during
> clock scaling. Enable multi-level gear scaling by mapping clock
> frequencies
> to gear speeds, so that when devfreq scales clock frequencies we can
> put
> the UFS link at the appropriate gear speeds accordingly.
> 
> Signed-off-by: Can Guo <quic_cang@quicinc.com>
> Co-developed-by: Ziqi Chen <quic_ziqichen@quicinc.com>
> Signed-off-by: Ziqi Chen <quic_ziqichen@quicinc.com>
> Reviewed-by: Bean Huo <beanhuo@micron.com>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
> ---
> 
> v1 -> v2:
> Rename the lable "do_pmc" to "config_pwr_mode".
> 
> v2 -> v3:
> Use assignment instead memcpy() in function ufshcd_scale_gear().
> 
> v3 -> v4:
> Typo fixed for commit message.
> ---
>  drivers/ufs/core/ufshcd.c | 51 +++++++++++++++++++++++++++++++------
> --
>  1 file changed, 41 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 8d295cc827cc..ebab897080a6 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1308,16 +1308,26 @@ static int
> ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
>  /**
>   * ufshcd_scale_gear - scale up/down UFS gear
>   * @hba: per adapter instance
> + * @target_gear: target gear to scale to
>   * @scale_up: True for scaling up gear and false for scaling down
>   *
>   * Return: 0 for success; -EBUSY if scaling can't happen at this
> time;
>   * non-zero for any other errors.
>   */
> -static int ufshcd_scale_gear(struct ufs_hba *hba, bool scale_up)
> +static int ufshcd_scale_gear(struct ufs_hba *hba, u32 target_gear,
> bool scale_up)
>  {
>         int ret = 0;
>         struct ufs_pa_layer_attr new_pwr_info;
> 
> +       if (target_gear) {
> +               new_pwr_info = hba->pwr_info;
> +               new_pwr_info.gear_tx = target_gear;
> +               new_pwr_info.gear_rx = target_gear;
> +
> +               goto config_pwr_mode;
> +       }
> +
> +       /* Legacy gear scaling, in case vops_freq_to_gear_speed() is
> not implemented */
>         if (scale_up) {
>                 memcpy(&new_pwr_info, &hba-
> >clk_scaling.saved_pwr_info,
>                        sizeof(struct ufs_pa_layer_attr));
> @@ -1338,6 +1348,7 @@ static int ufshcd_scale_gear(struct ufs_hba
> *hba, bool scale_up)
>                 }
>         }
> 
> +config_pwr_mode:
>         /* check if the power mode needs to be changed or not? */
>         ret = ufshcd_config_pwr_mode(hba, &new_pwr_info);
>         if (ret)
> @@ -1408,15 +1419,26 @@ static void
> ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, int err, bool sc
>  static int ufshcd_devfreq_scale(struct ufs_hba *hba, unsigned long
> freq,
>                                 bool scale_up)
>  {
> +       u32 old_gear = hba->pwr_info.gear_rx;
> +       int new_gear = 0;
>         int ret = 0;
> 
> +       new_gear = ufshcd_vops_freq_to_gear_speed(hba, freq);
> +       if (new_gear < 0)
> +               /*
> +                * return negative value means that the
> vops_freq_to_gear_speed() is not
> +                * implemented or didn't find matched gear speed,
> assign '0' to new_gear
> +                * to switch to legacy gear scaling sequence in
> ufshcd_scale_gear().
> +                */
> +               new_gear = 0;
> +
> 

Hi Ziqi,

I think remove help function is better. 
No need change new_gear type when use.
The readability is higher, and no need add that large amount comments.

       u32_new_gear = 0;
       if (hba->vops && hba->vops->freq_to_gear_speed)
               new_gear = hba->vops->freq_to_gear_speed(hba, freq);


Thanks.
Peter



>         ret = ufshcd_clock_scaling_prepare(hba, 1 * USEC_PER_SEC);
>         if (ret)
>                 return ret;
> 
>         /* scale down the gear before scaling down clocks */
>         if (!scale_up) {
> -               ret = ufshcd_scale_gear(hba, false);
> +               ret = ufshcd_scale_gear(hba, (u32)new_gear, false);
>                 if (ret)
>                         goto out_unprepare;
>         }
> @@ -1424,13 +1446,13 @@ static int ufshcd_devfreq_scale(struct
> ufs_hba *hba, unsigned long freq,
>         ret = ufshcd_scale_clks(hba, freq, scale_up);
>         if (ret) {
>                 if (!scale_up)
> -                       ufshcd_scale_gear(hba, true);
> +                       ufshcd_scale_gear(hba, old_gear, true);
>                 goto out_unprepare;
>         }
> 
>         /* scale up the gear after scaling up clocks */
>         if (scale_up) {
> -               ret = ufshcd_scale_gear(hba, true);
> +               ret = ufshcd_scale_gear(hba, (u32)new_gear, true);
>                 if (ret) {
>                         ufshcd_scale_clks(hba, hba->devfreq-
> >previous_freq,
>                                           false);
> @@ -1723,6 +1745,8 @@ static ssize_t
> ufshcd_clkscale_enable_store(struct device *dev,
>                 struct device_attribute *attr, const char *buf,
> size_t count)
>  {
>         struct ufs_hba *hba = dev_get_drvdata(dev);
> +       struct ufs_clk_info *clki;
> +       unsigned long freq;
>         u32 value;
>         int err = 0;
> 
> @@ -1746,14 +1770,21 @@ static ssize_t
> ufshcd_clkscale_enable_store(struct device *dev,
> 
>         if (value) {
>                 ufshcd_resume_clkscaling(hba);
> -       } else {
> -               ufshcd_suspend_clkscaling(hba);
> -               err = ufshcd_devfreq_scale(hba, ULONG_MAX, true);
> -               if (err)
> -                       dev_err(hba->dev, "%s: failed to scale clocks
> up %d\n",
> -                                       __func__, err);
> +               goto out_rel;
>         }
> 
> +       clki = list_first_entry(&hba->clk_list_head, struct
> ufs_clk_info, list);
> +       freq = clki->max_freq;
> +
> +       ufshcd_suspend_clkscaling(hba);
> +       err = ufshcd_devfreq_scale(hba, freq, true);
> +       if (err)
> +               dev_err(hba->dev, "%s: failed to scale clocks up
> %d\n",
> +                               __func__, err);
> +       else
> +               hba->clk_scaling.target_freq = freq;
> +
> +out_rel:
>         ufshcd_release(hba);
>         ufshcd_rpm_put_sync(hba);
>  out:
> --
> 2.34.1
>