Re: [PATCH v1 1/3] scsi: ufshcd: Update the set frequency to devfreq

From: Asutosh Das (asd)
Date: Wed Mar 25 2020 - 12:32:32 EST


On 3/25/2020 6:11 AM, Avri Altman wrote:

Currently, the frequency that devfreq provides the
driver to set always leads the clocks to be scaled up.
Hence, round the clock-rate to the nearest frequency
before deciding to scale.

Also update the devfreq statistics of current frequency.

Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
---
drivers/scsi/ufs/ufshcd.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 2a2a63b..4607bc6 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1187,6 +1187,9 @@ static int ufshcd_devfreq_target(struct device
*dev,
if (!ufshcd_is_clkscaling_supported(hba))
return -EINVAL;

+ clki = list_first_entry(&hba->clk_list_head, struct ufs_clk_info, list);
+ /* Override with the closest supported frequency */
+ *freq = (unsigned long) clk_round_rate(clki->clk, *freq);
spin_lock_irqsave(hba->host->host_lock, irq_flags);
Please remind me what the spin lock is protecting here?

Hmmm ... Nothing comes to my mind. I blamed it but it's a part of a bigger change.


if (ufshcd_eh_in_progress(hba)) {
spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
@@ -1201,8 +1204,13 @@ static int ufshcd_devfreq_target(struct device
*dev,
goto out;
}

- clki = list_first_entry(&hba->clk_list_head, struct ufs_clk_info, list);
+ /* Decide based on the rounded-off frequency and update */
scale_up = (*freq == clki->max_freq) ? true : false;
+ if (scale_up)
+ *freq = clki->max_freq;
This was already established 2 lines above ?
Good point - I'll change it.


+ else
+ *freq = clki->min_freq;
+ /* Update the frequency */
if (!ufshcd_is_devfreq_scaling_required(hba, scale_up)) {
spin_unlock_irqrestore(hba->host->host_lock, irq_flags);
ret = 0;
@@ -1250,6 +1258,8 @@ static int ufshcd_devfreq_get_dev_status(struct
device *dev,
struct ufs_hba *hba = dev_get_drvdata(dev);
struct ufs_clk_scaling *scaling = &hba->clk_scaling;
unsigned long flags;
+ struct list_head *clk_list = &hba->clk_list_head;
+ struct ufs_clk_info *clki;

if (!ufshcd_is_clkscaling_supported(hba))
return -EINVAL;
@@ -1260,6 +1270,8 @@ static int ufshcd_devfreq_get_dev_status(struct
device *dev,
if (!scaling->window_start_t)
goto start_window;

+ clki = list_first_entry(clk_list, struct ufs_clk_info, list);
+ stat->current_frequency = clki->curr_freq;
Is this a bug fix? > devfreq_simple_ondemand_func is trying to establish the busy period,
but also uses the frequency in its calculation - which I wasn't able to understand how.
Can you add a short comment why updating current_frequency is needed?

Sure - I'll add a comment. If stat->current_frequency is not updated, the governor would always ask to set the max freq because the initial frequency was unknown to it. Reference - devfreq_simple_ondemand_func(...)


Thanks,
Avri


Thanks,
-asd

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