From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Manasi Navare <manasi.d.navare@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Poll for DDI Idle status to be 0 after enabling DDI Buf
Date: Tue, 16 Jun 2020 22:54:22 +0300 [thread overview]
Message-ID: <20200616195422.GK6112@intel.com> (raw)
In-Reply-To: <20200616194244.GJ6112@intel.com>
On Tue, Jun 16, 2020 at 10:42:44PM +0300, Ville Syrjälä wrote:
> On Tue, Jun 16, 2020 at 12:30:56PM -0700, Manasi Navare wrote:
> > The Bspec sequence expects us to poll for DDI Idle status
> > to be 0 (not idle) with a timeout of 600usecs after enabling the
> > DDI BUF CTL.
>
> It only says that for newer platforms. We need to either keep
> the fixed delay before starting to poll, or someone needs confirm
> how the idle bit really behaves on the older platforms.
In fact it says not to use this bit at all on BXT. So even our disable
sequence is potentially borked on BXT. Unfortunately the spec doesn't
say which way the bit is broken, so not clear if that's the case or
not.
>
> > But currently in the driver we just wait for 600usecs
> > without polling so add that.
> >
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Imre Deak <imre.deak@intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> > drivers/gpu/drm/i915/display/intel_ddi.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index ca7bb2294d2b..de7e15de0bc5 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -4023,7 +4023,11 @@ static void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp)
> > intel_de_write(dev_priv, DDI_BUF_CTL(port), intel_dp->DP);
> > intel_de_posting_read(dev_priv, DDI_BUF_CTL(port));
> >
> > - udelay(600);
> > + if (wait_for_us(!(intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
> > + DDI_BUF_IS_IDLE),
> > + 600))
> > + drm_err(&dev_priv->drm, "DDI port:%c buffer idle\n",
> > + port_name(port));
> > }
> >
> > static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
> > --
> > 2.19.1
>
> --
> Ville Syrjälä
> Intel
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2020-06-16 19:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 19:30 [Intel-gfx] [PATCH] drm/i915/dp: Poll for DDI Idle status to be 0 after enabling DDI Buf Manasi Navare
2020-06-16 19:42 ` Ville Syrjälä
2020-06-16 19:54 ` Ville Syrjälä [this message]
2020-06-16 20:07 ` Manasi Navare
2020-06-16 20:22 ` Ville Syrjälä
2020-06-16 21:55 ` Manasi Navare
2020-06-16 23:11 ` [Intel-gfx] ✓ Fi.CI.BAT: success for " Patchwork
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200616195422.GK6112@intel.com \
--to=ville.syrjala@linux.intel.com \
--cc=intel-gfx@lists.freedesktop.org \
--cc=manasi.d.navare@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox