lkml.org 
[lkml]   [2020]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3/3] phy: sun4i-usb: Use power efficient workqueue for debounce and poll
From
Date
On 11/12/20 3:53 AM, Maxime Ripard wrote:
> On Tue, Nov 10, 2020 at 09:44:37PM -0600, Samuel Holland wrote:
>> On 11/9/20 6:12 AM, Frank Lee wrote:
>>> From: Yangtao Li <frank@allwinnertech.com>
>>>
>>> The debounce and poll time is generally quite long and the work not
>>> performance critical so allow the scheduler to run the work anywhere
>>> rather than in the normal per-CPU workqueue.
>>>
>>> Signed-off-by: Yangtao Li <frank@allwinnertech.com>
>>> ---
>>> drivers/phy/allwinner/phy-sun4i-usb.c | 14 +++++++-------
>>> 1 file changed, 7 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/phy/allwinner/phy-sun4i-usb.c b/drivers/phy/allwinner/phy-sun4i-usb.c
>>> index 651d5e2a25ce..4787ad13b255 100644
>>> --- a/drivers/phy/allwinner/phy-sun4i-usb.c
>>> +++ b/drivers/phy/allwinner/phy-sun4i-usb.c
>>> @@ -326,7 +326,7 @@ static int sun4i_usb_phy_init(struct phy *_phy)
>>> /* Force ISCR and cable state updates */
>>> data->id_det = -1;
>>> data->vbus_det = -1;
>>> - queue_delayed_work(system_wq, &data->detect, 0);
>>> + queue_delayed_work(system_power_efficient_wq, &data->detect, 0);
>>> }
>>>
>>> return 0;
>>> @@ -444,7 +444,7 @@ static int sun4i_usb_phy_power_on(struct phy *_phy)
>>>
>>> /* We must report Vbus high within OTG_TIME_A_WAIT_VRISE msec. */
>>
>> This doesn't sound like "not performance critical" to me. My understanding is
>> the debouncing has a deadline from the USB spec. Maybe this is more flexible
>> than the comment makes it sound?
>
> It's not really clear to me what the power_efficient workqueue brings to
> the table exactly from the comments on WQ_POWER_EFFICIENT (and the
> associated gmane link is long dead).
>
> It's only effect seems to be that it sets WQ_UNBOUND when the proper
> command line option is set, and WQ_UNBOUND allows for the scheduled work
> to run on any CPU instead of the local one.
>
> Given that we don't have any constraint on the CPU here, and the CPU
> locality shouldn't really make any difference, I'm not sure we should
> expect any meaningful difference.
>
> This is also what the rest of the similar drivers seem to be using:
> https://elixir.bootlin.com/linux/v5.10-rc3/source/drivers/usb/common/usb-conn-gpio.c#L119
> https://elixir.bootlin.com/linux/v5.10-rc3/source/drivers/usb/core/hub.c#L1254

Thanks for the explanation. Then the patch looks fine to me.

Reviewed-by: Samuel Holland <samuel@sholland.org>

Cheers,
Samuel

\
 
 \ /
  Last update: 2020-11-17 05:51    [W:0.068 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site