[PATCH v2] phy: renesas: rcar-gen3-usb2: Fix an error handling path in rcar_gen3_phy_usb2_probe()

[Biju Das]

Hi Christophe JAILLET,

Thanks for the patch.

> -----Original Message-----
> From: Christophe JAILLET <christophe.jaillet at wanadoo.fr>
> Sent: Saturday, September 7, 2024 2:59 PM
> Subject: [PATCH v2] phy: renesas: rcar-gen3-usb2: Fix an error handling path in
> rcar_gen3_phy_usb2_probe()
> 
> If an error occurs after the rcar_gen3_phy_usb2_init_bus(),
> reset_control_assert() must be called, as already done in the remove function.
> 
> This is fine to re-use the existing error handling path, because even if "channel->rstc" is still NULL
> at this point, it is safe to call reset_control_assert(NULL).
> 
> Fixes: 4eae16375357 ("phy: renesas: rcar-gen3-usb2: Add support to initialize the bus")
> Signed-off-by: Christophe JAILLET <christophe.jaillet at wanadoo.fr>
> ---
> Changes in v2:
>   - Re-use 'error' to simplify the patch   [claudiu beznea]
>   - Update the commit description to explain why it is safe.
> 
> v1:
> https://lore.kernel.org/all/fc9f7b444f0ca645411868992bbe16514aeccfed.1725652654.git.christophe.jaillet
> @wanadoo.fr/
> ---
>  drivers/phy/renesas/phy-rcar-gen3-usb2.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/phy/renesas/phy-rcar-gen3-usb2.c b/drivers/phy/renesas/phy-rcar-gen3-usb2.c
> index 58e123305152..ccb0b54b70f7 100644
> --- a/drivers/phy/renesas/phy-rcar-gen3-usb2.c
> +++ b/drivers/phy/renesas/phy-rcar-gen3-usb2.c
> @@ -803,6 +803,7 @@ static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
>  	return 0;
> 
>  error:
> +	reset_control_assert(channel->rstc);

This will result in either kernel crash [1] or reset usage count imbalance in case
of error [2] and [3] in rcar_gen3_phy_usb2_init_bus() see [4]. Also reset control API is not
respected for SoCs other than RZ/G3S. For those SoC's reset assert is
called without calling a get(). Maybe add a check (phy_data->init_bus) for
assert api's, that guarantees assert is called after calling a get() as it
valid only for RZ/G3S??

[1]
channel->rstc = devm_reset_control_array_get_shared(dev);
	if (IS_ERR(channel->rstc))
		return PTR_ERR(channel->rstc);

[2] 
ret = pm_runtime_resume_and_get(dev);
	if (ret)
		return ret;
[3]
ret = reset_control_deassert(channel->rstc);
	if (ret)
		goto rpm_put;

[4] https://elixir.bootlin.com/linux/v6.11-rc6/source/drivers/reset/core.c#L483

Cheers,
Biju

>  	pm_runtime_disable(dev);
> 
>  	return ret;
> --
> 2.46.0
>