linux-kernel - Re: [PATCH v3 1/3] phy: amlogic: phy-meson-gxl-usb2: fix shared reset controller use

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Message-ID: <44f6cc1f52e75cbbb8aebb0d4648c94ae479ef43.camel@pengutronix.de>
Date:   Mon, 22 Nov 2021 10:03:16 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Amjad Ouled-Ameur <aouledameur@...libre.com>, khilman@...libre.com
Cc:     balbi@...nel.org, jbrunet@...libre.com,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v3 1/3] phy: amlogic: phy-meson-gxl-usb2: fix shared
 reset controller use

Hi Amjad,

On Fri, 2021-11-12 at 17:28 +0100, Amjad Ouled-Ameur wrote:
> Use reset_control_rearm() call if an error occurs in case
> phy_meson_gxl_usb2_init() fails after reset() has been called ; or in case
> phy_meson_gxl_usb2_exit() is called i.e the resource is no longer used
> and the reset line may be triggered again by other devices.
> 
> reset_control_rearm() keeps use of triggered_count sane in the reset
> framework. Therefore, use of reset_control_reset() on shared reset line
> should be balanced with reset_control_rearm().
> 
> Signed-off-by: Amjad Ouled-Ameur <aouledameur@...libre.com>
> Reported-by: Jerome Brunet <jbrunet@...libre.com>
> ---
>  drivers/phy/amlogic/phy-meson-gxl-usb2.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/phy/amlogic/phy-meson-gxl-usb2.c b/drivers/phy/amlogic/phy-meson-gxl-usb2.c
> index 2b3c0d730f20..9a9c769ecabc 100644
> --- a/drivers/phy/amlogic/phy-meson-gxl-usb2.c
> +++ b/drivers/phy/amlogic/phy-meson-gxl-usb2.c
> @@ -110,8 +110,10 @@ static int phy_meson_gxl_usb2_init(struct phy *phy)
>  	int ret;
>
>  	ret = reset_control_reset(priv->reset);
> -	if (ret)
> +	if (ret) {
> +		reset_control_rearm(priv->reset);

I don't understand this. If reset_control_reset() returns an error for a
shared reset, it should have either
- returned before incrementing triggered_count, or
- incremented triggered_count, got a failed reset op, decremented
  triggered_count again

In both cases there should be no need to rearm.


regards
Philipp