Re: [PATCH v2] drm/msm/dpu: Correct dpu destroy and disable order

[Rajendra Nayak <rnayak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

On 11/2/2018 6:19 PM, Jayant Shekhar wrote:
> In case of msm drm bind failure, dpu_mdss_destroy is triggered.
> In this function, resources are freed and pm runtime disable is
> called, which triggers dpu_mdss_disable. Now in dpu_mdss_disable,
> driver tries to access a memory which is already freed. This
> results in kernel panic. Fix this by ensuring proper sequence
> of dpu destroy and disable calls.
> 
> Changes in v2:
>     - Removed double spacings [Jeykumar]
> 
> Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>

I was testing this patch out and in my setup I see that with this
change, during a dsi probe defer case, a dpu_mdss_enable() is called
followed by a dpu_mdss_destroy() but dpu_mdss_disable() is never called.

This results in a mismatch in clock usecount causing the mdp clocks to
stay enabled even with display turned off.

localhost ~ # cat /sys/kernel/debug/clk/clk_summary | grep mdss
  disp_cc_mdss_rscc_ahb_clk            0        0        0           0          0     0  50000
  disp_cc_mdss_axi_clk                 0        0        0           0          0     0  50000
  disp_cc_mdss_ahb_clk                 0        0        0           0          0     0  50000
        disp_cc_mdss_mdp_clk_src       1        1        0    19200000          0     0  50000
           disp_cc_mdss_mdp_lut_clk       0        0        0    19200000          0     0  50000
           disp_cc_mdss_mdp_clk        1        1        0    19200000          0     0  50000
        disp_cc_mdss_vsync_clk_src       0        0        0    19200000          0     0  50000

Also to note, on an older 4.14 kernel, I do not see any issue in the order in which
these functions are called in the dsi probe defer case, i.e its an enable followed by
a disable and then a destroy (and that's without this patch)

> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> index fd9c893..902bb4c 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> @@ -156,18 +156,15 @@ static void dpu_mdss_destroy(struct drm_device *dev)
>   	struct dpu_mdss *dpu_mdss = to_dpu_mdss(priv->mdss);
>   	struct dss_module_power *mp = &dpu_mdss->mp;
>   
> +	pm_runtime_disable(dev->dev);
>   	_dpu_mdss_irq_domain_fini(dpu_mdss);
> -
>   	free_irq(platform_get_irq(pdev, 0), dpu_mdss);
> -
>   	msm_dss_put_clk(mp->clk_config, mp->num_clk);
>   	devm_kfree(&pdev->dev, mp->clk_config);
>   
>   	if (dpu_mdss->mmio)
>   		devm_iounmap(&pdev->dev, dpu_mdss->mmio);
>   	dpu_mdss->mmio = NULL;
> -
> -	pm_runtime_disable(dev->dev);
>   	priv->mdss = NULL;
>   }
>   
> 
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