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Date: Thu, 31 Mar 2022 14:06:54 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Sankeerth Billakanti <sbillaka@....qualcomm.com>
Cc: "Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
"freedreno@...ts.freedesktop.org" <freedreno@...ts.freedesktop.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"robdclark@...il.com" <robdclark@...il.com>,
"seanpaul@...omium.org" <seanpaul@...omium.org>,
"swboyd@...omium.org" <swboyd@...omium.org>,
quic_kalyant <quic_kalyant@...cinc.com>,
"Abhinav Kumar (QUIC)" <quic_abhinavk@...cinc.com>,
"dianders@...omium.org" <dianders@...omium.org>,
"Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
"bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
"sean@...rly.run" <sean@...rly.run>,
"airlied@...ux.ie" <airlied@...ux.ie>,
"daniel@...ll.ch" <daniel@...ll.ch>,
quic_vproddut <quic_vproddut@...cinc.com>,
"Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>
Subject: Re: [PATCH v6 4/8] drm/msm/dp: avoid handling masked interrupts
On Thu, 31 Mar 2022 at 14:05, Sankeerth Billakanti
<sbillaka@....qualcomm.com> 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@...cinc.com> 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@...cinc.com>
> > >>> ---
> > >>> 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);
> >
>
> 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
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