RE: [PATCH v6 4/8] drm/msm/dp: avoid handling masked interrupts

[Sankeerth Billakanti (QUIC)]

> On Thu, 31 Mar 2022 at 14:05, Sankeerth Billakanti
> <sbillaka@xxxxxxxxxxxxxxxx> wrote:
> >
> > Hi Dmitry,
> >
> > > On 31/03/2022 08:53, Sankeerth Billakanti (QUIC) wrote:
> > > > Hi Dmitry,
> > > >
> > > >> On Wed, 30 Mar 2022 at 19:03, Sankeerth Billakanti
> > > >> <quic_sbillaka@xxxxxxxxxxx> wrote:
> > > >>>
> > > >>> The interrupt register will still reflect the connect and
> > > >>> disconnect interrupt status without generating an actual HW
> interrupt.
> > > >>> The controller driver should not handle those masked interrupts.
> > > >>>
> > > >>> Signed-off-by: Sankeerth Billakanti <quic_sbillaka@xxxxxxxxxxx>
> > > >>> ---
> > > >>>   drivers/gpu/drm/msm/dp/dp_catalog.c | 5 +++--
> > > >>>   1 file changed, 3 insertions(+), 2 deletions(-)
> > > >>>
> > > >>> diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.c
> > > >>> b/drivers/gpu/drm/msm/dp/dp_catalog.c
> > > >>> index 3c16f95..1809ce2 100644
> > > >>> --- a/drivers/gpu/drm/msm/dp/dp_catalog.c
> > > >>> +++ b/drivers/gpu/drm/msm/dp/dp_catalog.c
> > > >>> @@ -608,13 +608,14 @@ u32 dp_catalog_hpd_get_intr_status(struct
> > > >>> dp_catalog *dp_catalog)  {
> > > >>>          struct dp_catalog_private *catalog = container_of(dp_catalog,
> > > >>>                                  struct dp_catalog_private, dp_catalog);
> > > >>> -       int isr = 0;
> > > >>> +       int isr, mask;
> > > >>>
> > > >>>          isr = dp_read_aux(catalog, REG_DP_DP_HPD_INT_STATUS);
> > > >>>          dp_write_aux(catalog, REG_DP_DP_HPD_INT_ACK,
> > > >>>                                   (isr & DP_DP_HPD_INT_MASK));
> > > >>> +       mask = dp_read_aux(catalog, REG_DP_DP_HPD_INT_MASK);
> > > >>>
> > > >>> -       return isr;
> > > >>> +       return isr & (DP_DP_HPD_STATE_STATUS_MASK | mask);
> > > >>
> > > >> I suspect that the logic is inverted here. Shouldn't it be:
> > > >>
> > > >> return isr & DP_DP_HPD_STATE_STATUS_MASK & mask;
> > > >>
> > > >> ?
> > > >>
> > > >
> > > > The value of DP_DP_HPD_STATE_STATUS_MASK is 0xE0000000 and the
> > > value
> > > > of the read interrupt mask variable could be is 0xF.
> > > >
> > > > The mask value is indicated via the register,
> > > > REG_DP_DP_HPD_INT_MASK,
> > > bits 3:0.
> > > > The HPD status is indicated via a different read-only register
> > > REG_DP_DP_HPD_INT_STATUS, bits 31:29.
> > >
> > > I see. Maybe the following expression would be better?
> > >
> > > return isr & (mask & ~DP_DP_HPD_INT_MASK);
> 
> Ugh, excuse me please. I meant:
> 
> return isr & (mask | ~DP_DP_HPD_INT_MASK);
> 

Okay. I will change it.

> > >
> >
> > I believe the confusion occurred because the
> > DP_DP_HPD_STATE_STATUS_CONNECTED and others were defined under
> the same register definition as REG_DP_DP_HPD_INT_MASK I will rearrange
> the definitions below.
> >
> > #define REG_DP_DP_HPD_INT_MASK          (0x0000000C)
> > #define DP_DP_HPD_PLUG_INT_MASK         (0x00000001)
> > #define DP_DP_IRQ_HPD_INT_MASK          (0x00000002)
> > #define DP_DP_HPD_REPLUG_INT_MASK       (0x00000004)
> > #define DP_DP_HPD_UNPLUG_INT_MASK       (0x00000008)
> > #define DP_DP_HPD_INT_MASK              (DP_DP_HPD_PLUG_INT_MASK | \
> >                                                 DP_DP_IRQ_HPD_INT_MASK | \
> >                                                 DP_DP_HPD_REPLUG_INT_MASK | \
> >
> > DP_DP_HPD_UNPLUG_INT_MASK)
> >
> > Below are status bits from register REG_DP_DP_HPD_INT_STATUS
> >
> > #define DP_DP_HPD_STATE_STATUS_CONNECTED        (0x40000000)
> > #define DP_DP_HPD_STATE_STATUS_PENDING          (0x20000000)
> > #define DP_DP_HPD_STATE_STATUS_DISCONNECTED     (0x00000000)
> > #define DP_DP_HPD_STATE_STATUS_MASK             (0xE0000000)
> >
> > DP_DP_HPD_INT_MASK is 0xF and scope of mask variable is also 0xF (bits
> 3:0), mask & ~DP_DP_HPD_INT_MASK is 0 always.
> >
> > For DP, we want to enable all interrupts.
> > So the programmed mask value is 0xF. We want to return 0x40000001 for
> > connect and 8 for disconnect
> >
> > For eDP, we want to disable the connect and disconnect interrupts. So,
> > the mask will be 0x6 (i.e. DP_DP_IRQ_HPD_INT_MASK |
> DP_DP_HPD_REPLUG_INT_MASK) We want to return 0x40000000 (or
> 0x20000000 based on hpd line status) and 0 for eDP connect and disconnect
> respectively.
> >
> > > >
> > > > isr & DP_DP_HPD_STATE_STATUS_MASK & mask, will return 0 always.
> > > >
> > > >>>   }
> > > >>>
> > > >>>   int dp_catalog_ctrl_get_interrupt(struct dp_catalog
> > > >>> *dp_catalog)
> > > >>> --
> > > >>> 2.7.4
> > > >>>
> > > >>
> > > >>
> > > >> --
> > > >> With best wishes
> > > >> Dmitry
> > > >
> > > > Thank you,
> > > > Sankeerth
> > >
> > >
> > > --
> > > With best wishes
> > > Dmitry
> >
> > Thank you,
> > Sankeerth
> 
> 
> 
> --
> With best wishes
> Dmitry