linux-kernel - Re: [PATCH] drm: sun4i_tcon: use devm_clk_get_enabled in `sun4i_tcon_init

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Message-ID: <9935262d-a68b-edbf-0329-f755cbf99c45@hust.edu.cn>
Date:   Thu, 11 May 2023 14:18:39 +0800
From:   XuDong Liu <m202071377@...t.edu.cn>
To:     XuDong Liu <m202071377@...t.edu.cn>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     hust-os-kernel-patches@...glegroups.com,
        Dongliang Mu <dzm91@...t.edu.cn>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: sun4i_tcon: use devm_clk_get_enabled in
 `sun4i_tcon_init_clocks`

On 2023/4/30 19:23, XuDong Liu wrote:
> Smatch reports:
> drivers/gpu/drm/sun4i/sun4i_tcon.c:805 sun4i_tcon_init_clocks() warn:
> 'tcon->clk' from clk_prepare_enable() not released on lines: 792,801.
> 
> In the function sun4i_tcon_init_clocks(), tcon->clk and tcon->sclk0 are
> not disabled in the error handling, which affects the release of
> these variable. Although sun4i_tcon_bind(), which calls
> sun4i_tcon_init_clocks(), use sun4i_tcon_free_clocks to disable the
> variables mentioned, but the error handling branch of
> sun4i_tcon_init_clocks() ignores the required disable process.
> 
> To fix this issue, use the devm_clk_get_enabled to automatically
> balance enable and disabled calls. As original implementation use
> sun4i_tcon_free_clocks() to disable clk explicitly, we delete the
> related calls and error handling that are no longer needed.
> 
> Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support")
> Fixes: b14e945bda8a ("drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init")
> Fixes: 8e9240472522 ("drm/sun4i: support TCONs without channel 1")
> Fixes: 34d698f6e349 ("drm/sun4i: Add has_channel_0 TCON quirk")
> Signed-off-by: XuDong Liu <m202071377@...t.edu.cn>
> Reviewed-by: Dongliang Mu <dzm91@...t.edu.cn>
> ---
> The issue is discovered by static analysis, and the patch is not tested
> yet.
> ---
>   drivers/gpu/drm/sun4i/sun4i_tcon.c | 19 ++++---------------
>   1 file changed, 4 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index 523a6d787921..936796851ffd 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -778,21 +778,19 @@ static irqreturn_t sun4i_tcon_handler(int irq, void *private)
>   static int sun4i_tcon_init_clocks(struct device *dev,
>   				  struct sun4i_tcon *tcon)
>   {
> -	tcon->clk = devm_clk_get(dev, "ahb");
> +	tcon->clk = devm_clk_get_enabled(dev, "ahb");
>   	if (IS_ERR(tcon->clk)) {
>   		dev_err(dev, "Couldn't get the TCON bus clock\n");
>   		return PTR_ERR(tcon->clk);
>   	}
> -	clk_prepare_enable(tcon->clk);
>   
>   	if (tcon->quirks->has_channel_0) {
> -		tcon->sclk0 = devm_clk_get(dev, "tcon-ch0");
> +		tcon->sclk0 = devm_clk_get_enabled(dev, "tcon-ch0");
>   		if (IS_ERR(tcon->sclk0)) {
>   			dev_err(dev, "Couldn't get the TCON channel 0 clock\n");
>   			return PTR_ERR(tcon->sclk0);
>   		}
>   	}
> -	clk_prepare_enable(tcon->sclk0);
>   
>   	if (tcon->quirks->has_channel_1) {
>   		tcon->sclk1 = devm_clk_get(dev, "tcon-ch1");
> @@ -805,12 +803,6 @@ static int sun4i_tcon_init_clocks(struct device *dev,
>   	return 0;
>   }
>   
> -static void sun4i_tcon_free_clocks(struct sun4i_tcon *tcon)
> -{
> -	clk_disable_unprepare(tcon->sclk0);
> -	clk_disable_unprepare(tcon->clk);
> -}
> -
>   static int sun4i_tcon_init_irq(struct device *dev,
>   			       struct sun4i_tcon *tcon)
>   {
> @@ -1223,14 +1215,14 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
>   	ret = sun4i_tcon_init_regmap(dev, tcon);
>   	if (ret) {
>   		dev_err(dev, "Couldn't init our TCON regmap\n");
> -		goto err_free_clocks;
> +		goto err_assert_reset;
>   	}
>   
>   	if (tcon->quirks->has_channel_0) {
>   		ret = sun4i_dclk_create(dev, tcon);
>   		if (ret) {
>   			dev_err(dev, "Couldn't create our TCON dot clock\n");
> -			goto err_free_clocks;
> +			goto err_assert_reset;
>   		}
>   	}
>   
> @@ -1293,8 +1285,6 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
>   err_free_dotclock:
>   	if (tcon->quirks->has_channel_0)
>   		sun4i_dclk_free(tcon);
> -err_free_clocks:
> -	sun4i_tcon_free_clocks(tcon);
>   err_assert_reset:
>   	reset_control_assert(tcon->lcd_rst);
>   	return ret;
> @@ -1308,7 +1298,6 @@ static void sun4i_tcon_unbind(struct device *dev, struct device *master,
>   	list_del(&tcon->list);
>   	if (tcon->quirks->has_channel_0)
>   		sun4i_dclk_free(tcon);
> -	sun4i_tcon_free_clocks(tcon);
>   }
>   
>   static const struct component_ops sun4i_tcon_ops = {
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