linux-kernel - Re: [PATCH 08/10] ufs-qcom: phy/hcd: Refactoring phy clock handling

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Message-ID: <CAFp+6iE1X=-B=MhGBwcQHYnvn1ojZzSTqAFdJc+iFSOKbnYEuQ@mail.gmail.com>
Date:   Thu, 20 Oct 2016 09:14:51 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Subhash Jadavani <subhashj@...eaurora.org>
Cc:     kishon <kishon@...com>, jejb@...ux.vnet.ibm.com,
        Vinayak Holikatti <vinholikatti@...il.com>,
        martin.petersen@...cle.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-scsi@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 08/10] ufs-qcom: phy/hcd: Refactoring phy clock handling

On Thu, Oct 20, 2016 at 12:48 AM, Subhash Jadavani
<subhashj@...eaurora.org> wrote:
> On 2016-10-19 10:45, Vivek Gautam wrote:
>>
>> Hi,
>>
>>
>> On Wed, Oct 19, 2016 at 1:43 AM, Subhash Jadavani
>> <subhashj@...eaurora.org> wrote:
>>>
>>> On 2016-10-18 07:28, Vivek Gautam wrote:
>>>>
>>>>
>>>> Add phy clock enable code to phy_power_on/off callbacks, and
>>>> remove explicit calls to enable these phy clocks from the
>>>> ufs-qcom hcd driver.
>>>>
>>>> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
>>>> ---
>>>>
>>>> Changes since v1:
>>>>  - staticized ufs_qcom_phy_enable(/disable)_ref_clk(),
>>>>  - staticized ufs_qcom_phy_enable(/disable)_iface_clk()
>>>>  - removed function declaration and export symbol for these APIs.
>>
>>
>> [snip]
>>
>>>> --- a/drivers/scsi/ufs/ufs-qcom.c
>>>> +++ b/drivers/scsi/ufs/ufs-qcom.c
>>>> @@ -1112,17 +1112,6 @@ static int ufs_qcom_setup_clocks(struct ufs_hba
>>>> *hba, bool on)
>>>>                 return 0;
>>>>
>>>>         if (on) {
>>>> -               err = ufs_qcom_phy_enable_iface_clk(host->generic_phy);
>>>> -               if (err)
>>>> -                       goto out;
>>>> -
>>>> -               err = ufs_qcom_phy_enable_ref_clk(host->generic_phy);
>>>> -               if (err) {
>>>> -                       dev_err(hba->dev, "%s enable phy ref clock
>>>> failed,
>>>> err=%d\n",
>>>> -                               __func__, err);
>>>> -
>>>> ufs_qcom_phy_disable_iface_clk(host->generic_phy);
>>>> -                       goto out;
>>>> -               }
>>>
>>>
>>>
>>> Now that you are moving these ref clk enable/disable to phy_power_on/off
>>> and
>>> these phy_power_on/off are called only in runtime suspend/resume (3
>>> seconds
>>> after last UFS access).
>>> Goal is to disable the phy reference clock during aggressive gating (10ms
>>> from last UFS access) so shouldn't we call the phy_power_on/off from
>>> these
>>> setup_clocks() function as well?
>>>
>>
>> So setup_clocks() is called for aggressive clock gating as well ?
>> If that's the case then yes, we may need to call. But we should try to
>> understand here. The phy_power_off turns off all the clocks - reflclk,
>> and other interface clocks. Do we want all of them to be turned off ?
>
>
> Yes, we want to turn off the ref clock (& other clocks) during aggressive
> gating.

Ok.

>
>>
>> phy_power_off will also turn off the PHY. Do we want all this for
>> aggressive
>> clock gating ?
>
>
> Yes, PHY rails can be powered off both during the aggressive clk gating and
> runtime suspend. But as the regulator on/off latencies could be higher
> (especially for the shared rail), we were turning them off doing it in
> runtime suspend only (via phy_power_off()).
> Now that phy_power_on/off is managing both clocks and regulators, and we
> will really want to turn off the ref clocks during clock gating, there is no
> option but to call phy_power_on/off during aggressive gating.

Alright then, i will update the change to add phy_power_off/on()
during aggressive clock gating.


Thanks
Vivek

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