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

[Manivannan Sadhasivam <mani@kernel.org>]

On Thu, Jan 16, 2025 at 05:11:46PM +0800, Ziqi Chen wrote:
> 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 appropraite gear speeds accordingly.
> 
> Co-developed-by: Ziqi Chen <quic_ziqichen@quicinc.com>
> Signed-off-by: Ziqi Chen <quic_ziqichen@quicinc.com>
> Signed-off-by: Can Guo <quic_cang@quicinc.com>
> ---
>  drivers/ufs/core/ufshcd.c | 46 ++++++++++++++++++++++++++++++---------
>  1 file changed, 36 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 8d295cc827cc..839bc23aeda0 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1308,16 +1308,28 @@ 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) {
> +		memcpy(&new_pwr_info, &hba->pwr_info,
> +		       sizeof(struct ufs_pa_layer_attr));
> +
> +		new_pwr_info.gear_tx = target_gear;
> +		new_pwr_info.gear_rx = target_gear;
> +
> +		goto do_pmc;

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 +1350,7 @@ static int ufshcd_scale_gear(struct ufs_hba *hba, bool scale_up)
>  		}
>  	}
>  
> +do_pmc:
>  	/* check if the power mode needs to be changed or not? */
>  	ret = ufshcd_config_pwr_mode(hba, &new_pwr_info);
>  	if (ret)
> @@ -1408,15 +1421,19 @@ 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;
> +	u32 new_gear = 0;
>  	int ret = 0;
>  
> +	ufshcd_vops_freq_to_gear_speed(hba, freq, &new_gear);
> +
>  	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, new_gear, false);
>  		if (ret)
>  			goto out_unprepare;
>  	}
> @@ -1424,13 +1441,13 @@ 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, new_gear, true);
>  		if (ret) {
>  			ufshcd_scale_clks(hba, hba->devfreq->previous_freq,
>  					  false);
> @@ -1723,6 +1740,8 @@ 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 +1765,21 @@ 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;
> +

Just noticed that the 'clkscale_enable', 'clkgate_{delay_ms}/enable' sysfs
attributes have no ABI documentation. Please add them also in a separate patch.

- Mani

-- 
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