Re: [PATCH v1] of: platform: Batch fwnode parsing in the init_machine() path

[Saravana Kannan]

On Fri, Oct 2, 2020 at 11:35 AM 'Grygorii Strashko' via kernel-team
<kernel-team@xxxxxxxxxxx> wrote:
>
> hi Saravana,
>
> On 02/10/2020 21:27, Laurent Pinchart wrote:
> > Hi Saravana,
> >
> > On Fri, Oct 02, 2020 at 10:58:55AM -0700, Saravana Kannan wrote:
> >> On Fri, Oct 2, 2020 at 10:55 AM Laurent Pinchart wrote:
> >>> On Fri, Oct 02, 2020 at 10:51:51AM -0700, Saravana Kannan wrote:
> >>>> On Fri, Oct 2, 2020 at 7:08 AM Rob Herring <robh+dt@xxxxxxxxxx> wrote:
> >>>>> On Thu, Oct 1, 2020 at 5:59 PM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
> >>>>>>
> >>>>>> When commit 93d2e4322aa7 ("of: platform: Batch fwnode parsing when
> >>>>>> adding all top level devices") optimized the fwnode parsing when all top
> >>>>>> level devices are added, it missed out optimizing this for platform
> >>>>>> where the top level devices are added through the init_machine() path.
> >>>>>>
> >>>>>> This commit does the optimization for all paths by simply moving the
> >>>>>> fw_devlink_pause/resume() inside of_platform_default_populate().
> >>>>>>
> >>>>>> Reported-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
> >>>>>> Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
> >>>>>> ---
> >>>>>>   drivers/of/platform.c | 19 +++++++++++++++----
> >>>>>>   1 file changed, 15 insertions(+), 4 deletions(-)
> >>>>>>
> >>>>>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> >>>>>> index 071f04da32c8..79972e49b539 100644
> >>>>>> --- a/drivers/of/platform.c
> >>>>>> +++ b/drivers/of/platform.c
> >>>>>> @@ -501,8 +501,21 @@ int of_platform_default_populate(struct device_node *root,
> >>>>>>                                   const struct of_dev_auxdata *lookup,
> >>>>>>                                   struct device *parent)
> >>>>>>   {
> >>>>>> -       return of_platform_populate(root, of_default_bus_match_table, lookup,
> >>>>>> -                                   parent);
> >>>>>> +       int ret;
> >>>>>> +
> >>>>>> +       /*
> >>>>>> +        * fw_devlink_pause/resume() are only safe to be called around top
> >>>>>> +        * level device addition due to locking constraints.
> >>>>>> +        */
> >>>>>> +       if (!root)
> >>>>>> +               fw_devlink_pause();
> >>>>>> +
> >>>>>> +       ret = of_platform_populate(root, of_default_bus_match_table, lookup,
> >>>>>> +                                  parent);
> >>>>>
> >>>>> of_platform_default_populate() vs. of_platform_populate() is just a
> >>>>> different match table. I don't think the behavior should otherwise be
> >>>>> different.
> >>>>>
> >>>>> There's also of_platform_probe() which has slightly different matching
> >>>>> behavior. It should not behave differently either with respect to
> >>>>> devlinks.
> >>>>
> >>>> So I'm trying to do this only when the top level devices are added for
> >>>> the first time. of_platform_default_populate() seems to be the most
> >>>> common path. For other cases, I think we just need to call
> >>>> fw_devlink_pause/resume() wherever the top level devices are added for
> >>>> the first time. As I said in the other email, we can't add
> >>>> fw_devlink_pause/resume() by default to of_platform_populate().
> >>>>
> >>>> Do you have other ideas for achieving "call fw_devlink_pause/resume()
> >>>> only when top level devices are added for the first time"?
> >>>
> >>> I'm not an expert in this domain, but before investigating it, would you
> >>> be able to share a hack patch that implements this (in the most simple
> >>> way) to check if it actually fixes the delays I experience on my system
> >>> ?
> >>
> >> So I take it the patch I sent out didn't work for you? Can you tell me
> >> what machine/DT you are using?
> >
> > I've replied to the patch:
> >
> > Based on v5.9-rc5, before the patch:
> >
> > [    0.652887] cpuidle: using governor menu
> > [   12.349476] No ATAGs?
> >
> > After the patch:
> >
> > [    0.650460] cpuidle: using governor menu
> > [   12.262101] No ATAGs?
> >
> > I'm using an AM57xx EVM, whose DT is not upstream, but it's essentially
> > a am57xx-beagle-x15-revb1.dts (it includes that DTS) with a few
> > additional nodes for GPIO keys, LCD panel, backlight and touchscreen.
> >
>
> hope you are receiving my mails as I've provided you with all required information already [1]

Laurent/Grygorii,

Looks like I'm definitely missing emails. Sorry about the confusion.

I have some other urgent things on my plate right now. Is it okay if I
get to this in a day or two? In the end, we'll find a solution that
addresses most/all of the delay.

Thanks,
Saravana