linux-kernel - Re: [PATCH v1] reset: Make optional stuff optional for all users

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Date:   Mon, 03 Apr 2017 16:27:51 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Ramiro Oliveira <Ramiro.Oliveira@...opsys.com>
Subject: Re: [PATCH v1] reset: Make optional stuff optional for all users

Hi Andy,

thank you for the patch.

On Mon, 2017-04-03 at 15:26 +0300, Andy Shevchenko wrote:
> There is Device Tree oriented check for optional resource. Of course
> it will fail on non-DT platforms.
> 
> Remove this check to make things optional for all users.
> 
> Fixes: bb475230b8e5 ("reset: make optional functions really optional")
> Cc: Ramiro Oliveira <Ramiro.Oliveira@...opsys.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
> 
>  The reset framework is too Device Tree oriented, and who knows what
>  the logic was behind the commit which introduced devm_reset_*()
>  functions without thinking out of the DT box.

At the time, there was nothing outside of the box to describe reset
lines, and as far as I am aware there still isn't, so the devm_reset_*
should behave as if the reset line is not specified in the non-DT case.
Returning -EINVAL was reasonable in that case, before the API was
changed to describe unavailable, optional reset controls as rstc = NULL.

>  This commit fixes almost all Intel newest boards that have no legacy
>  UART since UART driver started using this DT-centric framework.

Is this is about 8250_dw.c? Unfortunately it sometimes takes a little
while for me to get updated on the big picture, as I only get the actual
reset driver and framework patches in my inbox. Usually I only see the
reset consumer changes when I actively look for them.

But the fault in this case was is with me not considering all possible
code paths influenced by commit bb475230b8e5, in the configurations that
I can't test myself.

>  drivers/reset/core.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
> index f1e5e65388bb..62314e663f29 100644
> --- a/drivers/reset/core.c
> +++ b/drivers/reset/core.c
> @@ -331,9 +331,6 @@ struct reset_control *__of_reset_control_get(struct device_node *node,

Ideally, __of_reset_control_get would not be called at all in the non-DT
case. I'll change that in the next round, but for now I'd prefer a small
fix in place.

>  	int rstc_id;
>  	int ret;
>  
> -	if (!node)
> -		return ERR_PTR(-EINVAL);
> -

This should be

	if (!node)
		return optional ? NULL : ERR_PTR(-EINVAL);

instead. Can you confirm this works for Intel boards with DW UART? I can
fix it up when applying if you agree.

>  	if (id) {
>  		index = of_property_match_string(node,
>  						 "reset-names", id);

regards
Philipp