linux-kernel - Re: [PATCH v1] of/platform: Unconditionally pause/resume sync state during kernel init

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Date:   Sat, 7 Dec 2019 22:53:10 -0600
From:   Frank Rowand <frowand.list@...il.com>
To:     Saravana Kannan <saravanak@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     kernel test robot <lkp@...el.com>, kernel-team@...roid.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] of/platform: Unconditionally pause/resume sync state
 during kernel init

On 12/6/19 7:03 PM, Saravana Kannan wrote:
> Commit 5e6669387e22 ("of/platform: Pause/resume sync state during init
> and of_platform_populate()") paused/resumed sync state during init only
> if Linux had parsed and populated a devicetree.
> 

I _think_ (but I have not actually checked the code) that enabling unittests
is not the only way that of_root can be changed from NULL (thus changing
the value returned by of_have_populated_dt()).  I _think_ that applying
an overlay on top of an empty devicetree will have the same result.  So
I would change the following paragraph:

> However, the check for that (of_have_populated_dt()) can change between
> initcall levels when device tree unittests are enabled. This causes an
> unmatched pause/resume of sync state. To avoid this, just
> unconditionally pause/resume sync state during init.

to something like:

However, the check for that (of_have_populated_dt()) can change
after of_platform_default_populate_init() executes.  One example
of this is when devicetree unittests are enabled.  This causes an
nmatched pause/resume of sync state. To avoid this, just
unconditionally pause/resume sync state during init.

> 
> Fixes: 5e6669387e22 ("of/platform: Pause/resume sync state during init and of_platform_populate()")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>  drivers/of/platform.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index d93891a05f60..3371e4a06248 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -518,10 +518,11 @@ static int __init of_platform_default_populate_init(void)
>  {
>  	struct device_node *node;
>  
> +	device_links_supplier_sync_state_pause();
> +
>  	if (!of_have_populated_dt())
>  		return -ENODEV;
>  
> -	device_links_supplier_sync_state_pause();
>  	/*
>  	 * Handle certain compatibles explicitly, since we don't want to create
>  	 * platform_devices for every node in /reserved-memory with a
> @@ -545,8 +546,7 @@ arch_initcall_sync(of_platform_default_populate_init);
>  
>  static int __init of_platform_sync_state_init(void)
>  {
> -	if (of_have_populated_dt())
> -		device_links_supplier_sync_state_resume();
> +	device_links_supplier_sync_state_resume();
>  	return 0;
>  }
>  late_initcall_sync(of_platform_sync_state_init);
> 

Reviewed-by: Frank Rowand <frowand.list@...il.com>