linux-kernel - Re: [PATCH v1] of: platform: Batch fwnode parsing in the init

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Date:   Fri, 2 Oct 2020 18:03:48 +0300
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Saravana Kannan <saravanak@...gle.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        <geert+renesas@...der.be>, <gregkh@...uxfoundation.org>,
        <linux-omap@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <peter.ujfalusi@...com>, <rjw@...ysocki.net>,
        <tomi.valkeinen@...com>, <tony@...mide.com>,
        <ulf.hansson@...aro.org>, <kernel-team@...roid.com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] of: platform: Batch fwnode parsing in the
 init_machine() path



On 02/10/2020 14:40, Grygorii Strashko wrote:
> 
> 
> On 02/10/2020 02:19, Laurent Pinchart wrote:
>> Hi Saravana,
>>
>> Thank you for the patch.
>>
>> On Thu, Oct 01, 2020 at 03:59:51PM -0700, Saravana Kannan 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().
>>
>> 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?
>>
>> :-(
> 
> This is kinda expected :( because omap2 arch doesn't call of_platform_default_populate()
> 
> Call path:
> board-generic.c
>   DT_MACHINE_START()
>     .init_machine    = omap_generic_init,
> 
>   omap_generic_init()
>     pdata_quirks_init(omap_dt_match_table);
>          of_platform_populate(NULL, omap_dt_match_table,
>                   omap_auxdata_lookup, NULL);
> 
> Other affected platforms
> arm: mach-ux500
> some mips
> some powerpc
> 
> there are also case when a lot of devices placed under bus node, in such case
>   of_platform_populate() calls from bus drivers will also suffer from this issue.
> 
> I think one option could be to add some parameter to _populate() or introduce new api.
> 
> By the way, is there option to disable this feature at all?
> Is there Kconfig option?
> Is there any reasons why such complex and time consuming code added to the kernel and not implemented on DTC level?
> 
> 
> Also, I've came with another diff, pls check.
> 
> [    0.000000] Booting Linux on physical CPU 0x0
> [    0.000000] Linux version 5.9.0-rc6-01791-g9acba6b38757-dirty (grygorii@...gorii-XPS-13-9370) (arm-linux-gnueabihf-gcc (GNU Toolcha0
> [    0.000000] CPU: ARMv7 Processor [412fc0f2] revision 2 (ARMv7), cr=10c5387d
> [    0.000000] CPU: div instructions available: patching division code
> [    0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
> [    0.000000] OF: fdt: Machine model: TI AM5718 IDK
> ...
> [    0.053443] cpuidle: using governor ladder
> [    0.053470] cpuidle: using governor menu
> [    0.089304] No ATAGs?
> ...
> [    3.092291] devtmpfs: mounted
> [    3.095804] Freeing unused kernel memory: 1024K
> [    3.100483] Run /sbin/init as init process
> 
> 
> 
> ------ >< ---
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 071f04da32c8..4521b26e7745 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -514,6 +514,12 @@ static const struct of_device_id reserved_mem_matches[] = {
>          {}
>   };
> 
> +static int __init of_platform_fw_devlink_pause(void)
> +{
> +       fw_devlink_pause();
> +}
> +core_initcall(of_platform_fw_devlink_pause);
> +
>   static int __init of_platform_default_populate_init(void)
>   {
>          struct device_node *node;
> @@ -538,9 +544,7 @@ static int __init of_platform_default_populate_init(void)
>          }
> 
>          /* Populate everything else. */
> -       fw_devlink_pause();
>          of_platform_default_populate(NULL, NULL, NULL);
> -       fw_devlink_resume();
> 
>          return 0;
>   }
> @@ -548,6 +552,7 @@ arch_initcall_sync(of_platform_default_populate_init);
> 
>   static int __init of_platform_sync_state_init(void)
>   {
> +       fw_devlink_resume();

^ it seems has to be done earlier, like
+static int __init of_platform_fw_devlink_resume(void)
+{
+       fw_devlink_resume();
+       return 0;
+}
+device_initcall_sync(of_platform_fw_devlink_resume);


>          device_links_supplier_sync_state_resume();
>          return 0;
>   }
> 
> 
> 

-- 
Best regards,
grygorii