Re: [Freedreno] [PATCH] drm/msm/dsi: do not install irq handler before power up the host

[abhinavk@xxxxxxxxxxxxxx]

On 2021-09-21 10:47, Dmitry Baryshkov wrote:
> Hi,
>
> On Tue, 21 Sept 2021 at 20:01, <abhinavk@xxxxxxxxxxxxxx> wrote:
> > On 2021-09-21 09:22, Dmitry Baryshkov wrote:
> > > The DSI host might be left in some state by the bootloader. If this
> > > state generates an IRQ, it might hang the system by holding the
> > > interrupt line before the driver sets up the DSI host to the known
> > > state.
> > >
> > > Move the request/free_irq calls into msm_dsi_host_power_on/_off calls,
> > > so that we can be sure that the interrupt is delivered when the host is
> > > in the known state.
> > >
> > > Fixes: a689554ba6ed ("drm/msm: Initial add DSI connector support")
> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> >
> > This is a valid change and we have seen interrupt storms in downstream
> > happening
> > when like you said the bootloader leaves the DSI host in unknown 
> > state.
> > Just one question below.
> >
> > > ---
> > >  drivers/gpu/drm/msm/dsi/dsi_host.c | 21 ++++++++++++---------
> > >  1 file changed, 12 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > index e269df285136..cd842347a6b1 100644
> > > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > > @@ -1951,15 +1951,6 @@ int msm_dsi_host_modeset_init(struct
> > > mipi_dsi_host *host,
> > >               return ret;
> > >       }
> > >
> > > -     ret = devm_request_irq(&pdev->dev, msm_host->irq,
> > > -                     dsi_host_irq, IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
> > > -                     "dsi_isr", msm_host);
> > > -     if (ret < 0) {
> > > -             DRM_DEV_ERROR(&pdev->dev, "failed to request IRQ%u: %d\n",
> > > -                             msm_host->irq, ret);
> > > -             return ret;
> > > -     }
> > > -
> > >       msm_host->dev = dev;
> > >       ret = cfg_hnd->ops->tx_buf_alloc(msm_host, SZ_4K);
> > >       if (ret) {
> > > @@ -2413,6 +2404,16 @@ int msm_dsi_host_power_on(struct mipi_dsi_host
> > > *host,
> > >       if (msm_host->disp_en_gpio)
> > >               gpiod_set_value(msm_host->disp_en_gpio, 1);
> > >
> > > +     ret = devm_request_irq(&msm_host->pdev->dev, msm_host->irq,
> > > +                     dsi_host_irq, IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
> > > +                     "dsi_isr", msm_host);
> > > +     if (ret < 0) {
> > > +             DRM_DEV_ERROR(&msm_host->pdev->dev, "failed to request IRQ%u: %d\n",
> > > +                             msm_host->irq, ret);
> > > +             return ret;
> > > +     }
> > > +
> > > +
> >
> > Do you want to move this to msm_dsi_host_enable()?
> > So without the controller being enabled it is still in unknown state?
>
> msm_dsi_host_power_on() reconfigures the host registers, so the state
> is known at the end of the power_on().
>
> > Also do you want to do this after dsi0 and dsi1 are initialized to
> > account for
> > dual dsi cases?
>
> I don't think this should matter. The host won't generate 'extra'
> interrupts in such case, will it?
We have seen cases where misconfiguration has caused interrupts to storm 
only
on one DSI in some cases. So yes, I would prefer this is done after both 
are
configured.

> > >       msm_host->power_on = true;
> > >       mutex_unlock(&msm_host->dev_mutex);
> > >
> > > @@ -2439,6 +2440,8 @@ int msm_dsi_host_power_off(struct mipi_dsi_host
> > > *host)
> > >               goto unlock_ret;
> > >       }
> > >
> > > +     devm_free_irq(&msm_host->pdev->dev, msm_host->irq, msm_host);
> > > +
> > >       dsi_ctrl_config(msm_host, false, NULL, NULL);
> > >
> > >       if (msm_host->disp_en_gpio)