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Subject: Re: [PATCH v1] of: platform: Batch fwnode parsing in the
 init_machine() path
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Saravana Kannan <saravanak@google.com>
CC:     Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-omap <linux-omap@vger.kernel.org>,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        Peter Ujfalusi <peter.ujfalusi@ti.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Tony Lindgren <tony@atomide.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Android Kernel Team <kernel-team@android.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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From:   Grygorii Strashko <grygorii.strashko@ti.com>
Message-ID: <11018e7e-a6a1-2df6-5639-821a7c0cb68b@ti.com>
Date:   Fri, 2 Oct 2020 21:35:49 +0300
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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@kernel.org> wrote:
>>>>> On Thu, Oct 1, 2020 at 5:59 PM Saravana Kannan <saravanak@google.com> 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@ti.com>
>>>>>> Signed-off-by: Saravana Kannan <saravanak@google.com>
>>>>>> ---
>>>>>>   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]

with below diff:
[    4.177231] Freeing unused kernel memory: 1024K
[    4.181892] Run /sbin/init as init process

The best time with [2] is
[    3.100483] Run /sbin/init as init process

Still 1 sec lose.

Pls understand an issue - requirements here are like 500ms boot with can, Ethernet, camera and display on ;(

[1] https://lore.kernel.org/patchwork/patch/1316134/#1511276
[2] https://lore.kernel.org/patchwork/patch/1316134/#1511435

diff --git a/arch/arm/mach-omap2/pdata-quirks.c b/arch/arm/mach-omap2/pdata-quirks.c
index 2a4fe3e68b82..ac1ab8928190 100644
--- a/arch/arm/mach-omap2/pdata-quirks.c
+++ b/arch/arm/mach-omap2/pdata-quirks.c
@@ -591,7 +591,9 @@ void __init pdata_quirks_init(const struct of_device_id *omap_dt_match_table)
         if (of_machine_is_compatible("ti,omap3"))
                 omap3_mcbsp_init();
         pdata_quirks_check(auxdata_quirks);
+       fw_devlink_pause();
         of_platform_populate(NULL, omap_dt_match_table,
                              omap_auxdata_lookup, NULL);
+       fw_devlink_resume();
         pdata_quirks_check(pdata_quirks);
  }


-- 
Best regards,
grygorii