Hi Can,

On Wed, 2020-02-19 at 18:33 +0800, Can Guo wrote:

Hi Stanley,

On 2020-02-19 17:11, Stanley Chu wrote:

quoted

Hi Can,

On Wed, 2020-02-19 at 10:35 +0800, Can Guo wrote:

quoted

Since we all need this delay here, how about put the delay in the
entrence of ufshcd_setup_clocks(), before vops_setup_clocks()?
If so, we can remove all the delays we added in our vops since the
delay anyways delays everything inside ufshcd_setup_clocks().

Always putting the delay in the entrance of ufshcd_setup_clocks() may
add unwanted delay for vendors, just like your current implementation,
or some other vendors who do not want to disable the reference clock.

I think current patch is more reasonable because the delay is applied 
to
clock only named as "ref_clk" specifically.

If you needs to keep "ref_clk" in DT, would you consider to remove the
delay in your ufs_qcom_dev_ref_clk_ctrl() and let the delay happens via
common ufshcd_setup_clocks() only? However you may still need delay if
call path comes from ufs_qcom_pwr_change_notify().

What do you think?

I agree current change is more reasonable from what it looks, but the 
fact
is that I canont remove the delay in ufs_qcom_dev_ref_clk_ctrl() even 
with
this change. On our platforms, ref_clk in DT serves multipule purposes,
the ref_clk provided to UFS device is actually controlled in
ufs_qcom_dev_ref_clk_ctrl(), which comes before where this change kicks 
start,
so if I remove the delay in ufs_qcom_dev_ref_clk_ctrl(), this change 
cannot
provide us the correct delay before gate the ref_clk provided to UFS 
device.

quoted

Always putting the delay in the entrance of ufshcd_setup_clocks() may
add unwanted delay for vendors, just like your current implementation,
or some other vendors who do not want to disable the reference clock.

I meant if we put the delay in the entrance, I will be able to remove
the delay in ufs_qcom_dev_ref_clk_ctrl(). Meanwhile, we can add proper
checks before the delay to make sure it is initiated only if ref_clk 
needs
to be disabled, i.e:

if(!on && !skip_ref_clk && hba->dev_info.clk_gating_wait_us)
     usleep_range();

Does this look better to you?

Firstly thanks so much for above details.

Again this statement may also add unwanted delay if some other vendors
does not have "ref_clk" in DT or they don't/can't disable the reference
clock provided to UFS device.

Anyways, we will see regressions with this change on our platforms, can 
we
have more discussions before get it merged? It should be OK if you go 
with
patch #2 alone first, right? Thanks.

Now the fact is that this change will impact your flow and it seems no
solid conclusion yet. Sure I could drop patch #1 and submit patch #2
only first : )

Thanks,
Stanley Chu



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