linux-kernel - Re: [PATCH v3 3/4] drm/msm: add a kernel param to select between MDP5 and DPU drivers

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Message-ID: <CAA8EJpoF3uKobGzjHbLMKYvcQbdqYzur7Mn1cNDPyc+wiiZ+SQ@mail.gmail.com>
Date: Sat, 6 Jan 2024 02:38:57 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Carl Vanderlip <quic_carlv@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH v3 3/4] drm/msm: add a kernel param to select between MDP5
 and DPU drivers

On Sat, 6 Jan 2024 at 02:04, Carl Vanderlip <quic_carlv@...cinc.com> wrote:
>
>
> On 1/5/2024 3:34 PM, Dmitry Baryshkov wrote:
> > For some of the platforms (e.g. SDM660, SDM630, MSM8996, etc.) it is
> > possible to support this platform via the DPU driver (e.g. to provide
> > support for DP, multirect, etc). Add a modparam to be able to switch
> > between these two drivers.
> >
> > All platforms supported by both drivers are by default handled by the
> > MDP5 driver. To let them be handled by the DPU driver pass the
> > `msm.prefer_mdp5=false` kernel param.
> >
> > Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c  |  3 +++
> >   drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c |  3 +++
> >   drivers/gpu/drm/msm/msm_drv.c            | 31 +++++++++++++++++++++++++++++++
> >   drivers/gpu/drm/msm/msm_drv.h            |  1 +
> >   4 files changed, 38 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > index aa9e0ad33ebb..8f11a98491a1 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > @@ -1276,6 +1276,9 @@ static int dpu_dev_probe(struct platform_device *pdev)
> >       int irq;
> >       int ret = 0;
> >
> > +     if (!msm_disp_drv_should_bind(&pdev->dev, true))
> > +             return -ENODEV;
> > +
> >       dpu_kms = devm_kzalloc(dev, sizeof(*dpu_kms), GFP_KERNEL);
> >       if (!dpu_kms)
> >               return -ENOMEM;
> > diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> > index 0827634664ae..43d05851c54d 100644
> > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> > @@ -866,6 +866,9 @@ static int mdp5_dev_probe(struct platform_device *pdev)
> >
> >       DBG("");
> >
> > +     if (!msm_disp_drv_should_bind(&pdev->dev, false))
> > +             return -ENODEV;
> > +
> >       mdp5_kms = devm_kzalloc(&pdev->dev, sizeof(*mdp5_kms), GFP_KERNEL);
> >       if (!mdp5_kms)
> >               return -ENOMEM;
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> > index 50b65ffc24b1..ef57586fbeca 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > @@ -969,6 +969,37 @@ static int add_components_mdp(struct device *master_dev,
> >       return 0;
> >   }
> >
> > +#if !IS_REACHABLE(CONFIG_DRM_MSM_MDP5) || !IS_REACHABLE(CONFIG_DRM_MSM_DPU)
> > +bool msm_disp_drv_should_bind(struct device *dev, bool mdp5_driver)
>
> s/mdp5_driver/dpu_driver/

Well, ignored_driver, but your suggestion is better.

>
> > +{
> > +     /* If just a single driver is enabled, use it no matter what */
> > +     return true;
> > +}
>
> This will cause both MDP/DPU probes to return -ENODEV, rather than
> select the enabled one.

No. The code (e.g. for DPU) is:

       if (!msm_disp_drv_should_bind(&pdev->dev, true))
                return -ENODEV;

So the driver returns -ENODEV if msm_disp_drv_should_bind() returns
false. Which is logical from the function name point of view.

>
> > +#else
> > +
> > +static bool prefer_mdp5 = true;
> > +MODULE_PARM_DESC(prefer_mdp5, "Select whether MDP5 or DPU driver should be preferred");
> > +module_param(prefer_mdp5, bool, 0444);
> > +
> > +/* list all platforms supported by both mdp5 and dpu drivers */
> > +static const char *const msm_mdp5_dpu_migration[] = {
> > +     NULL,
> > +};
> > +
> > +bool msm_disp_drv_should_bind(struct device *dev, bool dpu_driver)
> > +{
> > +     /* If it is not an MDP5 device, do not try MDP5 driver */
> > +     if (!of_device_is_compatible(dev->of_node, "qcom,mdp5"))
> > +             return dpu_driver;
> > +
> > +     /* If it is not in the migration list, use MDP5 */
> > +     if (!of_device_compatible_match(dev->of_node, msm_mdp5_dpu_migration))
> > +             return !dpu_driver;
> > +
> > +     return prefer_mdp5 ? !dpu_driver : dpu_driver;
> > +}
> > +#endif
> > +
> >   /*
> >    * We don't know what's the best binding to link the gpu with the drm device.
> >    * Fow now, we just hunt for all the possible gpus that we support, and add them
> > diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> > index 01e783130054..762e13e2df74 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.h
> > +++ b/drivers/gpu/drm/msm/msm_drv.h
> > @@ -563,5 +563,6 @@ int msm_drv_probe(struct device *dev,
> >       struct msm_kms *kms);
> >   void msm_kms_shutdown(struct platform_device *pdev);
> >
> > +bool msm_disp_drv_should_bind(struct device *dev, bool dpu_driver);
> >
> >   #endif /* __MSM_DRV_H__ */
> >



-- 
With best wishes
Dmitry