linux-kernel - Re: [PATCH V2 3/8] drm/msm: Unconditionally call dev_pm_opp_of_remove

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Date:   Tue, 1 Sep 2020 13:01:47 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
        Douglas Anderson <dianders@...omium.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 3/8] drm/msm: Unconditionally call
 dev_pm_opp_of_remove_table()


On 8/28/2020 11:37 AM, Viresh Kumar wrote:
> dev_pm_opp_of_remove_table() doesn't report any errors when it fails to
> find the OPP table with error -ENODEV (i.e. OPP table not present for
> the device). And we can call dev_pm_opp_of_remove_table()
> unconditionally here.

Its a little tricky to call things unconditionally for this driver, more below.

> 
> While at it, also create a label to put clkname.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> 
> ---
> V2:
> - Compare with -ENODEV only for failures.
> - Create new label to put clkname.
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 14 +++++---------
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h |  1 -
>   drivers/gpu/drm/msm/dsi/dsi_host.c      |  8 ++------
>   3 files changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index c0a4d4e16d82..c8287191951f 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -1010,12 +1010,9 @@ static int dpu_bind(struct device *dev, struct device *master, void *data)
>   		return PTR_ERR(dpu_kms->opp_table);
>   	/* OPP table is optional */
>   	ret = dev_pm_opp_of_add_table(dev);
> -	if (!ret) {
> -		dpu_kms->has_opp_table = true;
> -	} else if (ret != -ENODEV) {
> +	if (ret && ret != -ENODEV) {
>   		dev_err(dev, "invalid OPP table in device tree\n");
> -		dev_pm_opp_put_clkname(dpu_kms->opp_table);
> -		return ret;
> +		goto put_clkname;

So FWIU, dpu_unbind() gets called even when dpu_bind() fails for some reason.
I tried to address that earlier [1] which I realized did not land. But with these changes
it will be even more broken unless we identify if we failed dpu_bind() before
adding the OPP table, while adding it, or all went well with opps and handle things
accordingly in dpu_unbind.

[1] https://lore.kernel.org/patchwork/patch/1275632/

>   	}
>   
>   	mp = &dpu_kms->mp;
> @@ -1037,8 +1034,8 @@ static int dpu_bind(struct device *dev, struct device *master, void *data)
>   	priv->kms = &dpu_kms->base;
>   	return ret;
>   err:
> -	if (dpu_kms->has_opp_table)
> -		dev_pm_opp_of_remove_table(dev);
> +	dev_pm_opp_of_remove_table(dev);
> +put_clkname:
>   	dev_pm_opp_put_clkname(dpu_kms->opp_table);
>   	return ret;
>   }
> @@ -1056,8 +1053,7 @@ static void dpu_unbind(struct device *dev, struct device *master, void *data)
>   	if (dpu_kms->rpm_enabled)
>   		pm_runtime_disable(&pdev->dev);
>   
> -	if (dpu_kms->has_opp_table)
> -		dev_pm_opp_of_remove_table(dev);
> +	dev_pm_opp_of_remove_table(dev);
>   	dev_pm_opp_put_clkname(dpu_kms->opp_table);
>   }
>   
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> index e140cd633071..8295979a7165 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> @@ -129,7 +129,6 @@ struct dpu_kms {
>   	bool rpm_enabled;
>   
>   	struct opp_table *opp_table;
> -	bool has_opp_table;
>   
>   	struct dss_module_power mp;
>   
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index b17ac6c27554..4335fe33250c 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -113,7 +113,6 @@ struct msm_dsi_host {
>   	struct clk *byte_intf_clk;
>   
>   	struct opp_table *opp_table;
> -	bool has_opp_table;
>   
>   	u32 byte_clk_rate;
>   	u32 pixel_clk_rate;
> @@ -1891,9 +1890,7 @@ int msm_dsi_host_init(struct msm_dsi *msm_dsi)
>   		return PTR_ERR(msm_host->opp_table);
>   	/* OPP table is optional */
>   	ret = dev_pm_opp_of_add_table(&pdev->dev);
> -	if (!ret) {
> -		msm_host->has_opp_table = true;
> -	} else if (ret != -ENODEV) {
> +	if (ret && ret != -ENODEV) {
>   		dev_err(&pdev->dev, "invalid OPP table in device tree\n");
>   		dev_pm_opp_put_clkname(msm_host->opp_table);
>   		return ret;
> @@ -1934,8 +1931,7 @@ void msm_dsi_host_destroy(struct mipi_dsi_host *host)
>   	mutex_destroy(&msm_host->cmd_mutex);
>   	mutex_destroy(&msm_host->dev_mutex);
>   
> -	if (msm_host->has_opp_table)
> -		dev_pm_opp_of_remove_table(&msm_host->pdev->dev);
> +	dev_pm_opp_of_remove_table(&msm_host->pdev->dev);
>   	dev_pm_opp_put_clkname(msm_host->opp_table);
>   	pm_runtime_disable(&msm_host->pdev->dev);
>   }
> 

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