linux-kernel - Re: [PATCH 4/4] ath10k: snoc: fix unbalanced clock error handling

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Message-ID: <CAD=FV=XFUeyYZ-LQwYHeQH=b0kBf_wM5ZywpQDS74+_zqeDhEw@mail.gmail.com>
Date:   Tue, 16 Oct 2018 16:53:52 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     kvalo@....qualcomm.com, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org,
        Govind Singh <govinds@...eaurora.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] ath10k: snoc: fix unbalanced clock error handling

Hi,
On Fri, Oct 12, 2018 at 5:55 PM Brian Norris <briannorris@...omium.org> wrote:
>
> Similar to regulator error handling, we should only start tearing down
> the 'i - 1' clock when clock 'i' fails to enable. Otherwise, we might
> end up with an unbalanced clock, where we never successfully enabled the
> clock, but we try to disable it anyway.
>
> Signed-off-by: Brian Norris <briannorris@...omium.org>

Presumably you could have a Fixes tag just to help folks, like:

Fixes: a6a793f98786 ("ath10k: vote for hardware resources for WCN3990")

> ---
>  drivers/net/wireless/ath/ath10k/snoc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/snoc.c b/drivers/net/wireless/ath/ath10k/snoc.c
> index 5a8e87339df2..a835599a8d55 100644
> --- a/drivers/net/wireless/ath/ath10k/snoc.c
> +++ b/drivers/net/wireless/ath/ath10k/snoc.c
> @@ -1470,7 +1470,7 @@ static int ath10k_snoc_clk_init(struct ath10k *ar)
>         return 0;
>
>  err_clock_config:
> -       for (; i >= 0; i--) {
> +       for (i = i - 1; i >= 0; i--) {

I see no problem with this and it's a good / easy to backport fix.

Reviewed-by: Douglas Anderson <dianders@...omium.org>

For extra credit, though, you could change this to not duplicate the
"clk_bulk" APIs and just use 'em.  I already mentioned to someone else
that maybe the clk_bulk APIs could probably be improved to handle
optional clocks, but I don't think anyone has posted a patch for it.
Bonus points if you remember that "NULL" is a valid clock so you
really only need special case code in clk_bulk_get().  :-P


-Doug