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

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On 21/09/2021 23:52, abhinavk@xxxxxxxxxxxxxx wrote:
> 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.

I've checked. The power_on is called from dsi_mgr_bridge_pre_enable() 
when both DSI hosts should be bound.

> > > >       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)


--
With best wishes
Dmitry