On Thu, Oct 10, 2019 at 12:49 PM Sean Paul <sean@xxxxxxxxxx> wrote: > > On Thu, Oct 10, 2019 at 2:45 PM Sean Paul <sean@xxxxxxxxxx> wrote: > > > > On Wed, Oct 09, 2019 at 02:34:54PM -0700, Jeffrey Hugo wrote: > > > On msm8998, vblank timeouts are observed because the DSI controller is not > > > reset properly, which ends up stalling the MDP. This is because the reset > > > logic is not correct per the hardware documentation. > > > > > > The documentation states that after asserting reset, software should wait > > > some time (no indication of how long), or poll the status register until it > > > returns 0 before deasserting reset. > > > > > > wmb() is insufficient for this purpose since it just ensures ordering, not > > > timing between writes. Since asserting and deasserting reset occurs on the > > > same register, ordering is already guaranteed by the architecture, making > > > the wmb extraneous. > > > > > > Since we would define a timeout for polling the status register to avoid a > > > possible infinite loop, lets just use a static delay of 20 ms, since 16.666 > > > ms is the time available to process one frame at 60 fps. > > > > > > Fixes: a689554ba6ed (drm/msm: Initial add DSI connector support) > > > Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@xxxxxxxxx> > > > --- > > > > > > Rob et al, is it possible for this to go into a 5.4-rc? > > Sorry, I missed this on the first go-around, I'm Ok with this getting > into 5.4. Rob, if you're Ok with this, I can send it through -misc > unless you're planning an msm-fixes PR. > > > > > > > drivers/gpu/drm/msm/dsi/dsi_host.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c > > > index 663ff9f4fac9..68ded9b4735d 100644 > > > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c > > > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c > > > @@ -986,7 +986,7 @@ static void dsi_sw_reset(struct msm_dsi_host *msm_host) > > > wmb(); /* clocks need to be enabled before reset */ > > > > > > dsi_write(msm_host, REG_DSI_RESET, 1); > > > - wmb(); /* make sure reset happen */ > > > + msleep(20); /* make sure reset happen */ > > > > Could you please pull this out into a #define used for both in case we decide to > > tweak it? I don't want these 2 values to drift. > > Oh, yeah. That's a really good point. Will fix. > > oh yeah, and with that fixed, > > Reviewed-by: Sean Paul <sean@xxxxxxxxxx> Thanks. > > > Thanks, > > Sean > > > > > dsi_write(msm_host, REG_DSI_RESET, 0); > > > } > > > > > > @@ -1396,7 +1396,7 @@ static void dsi_sw_reset_restore(struct msm_dsi_host *msm_host) > > > > > > /* dsi controller can only be reset while clocks are running */ > > > dsi_write(msm_host, REG_DSI_RESET, 1); > > > - wmb(); /* make sure reset happen */ > > > + msleep(20); /* make sure reset happen */ > > > dsi_write(msm_host, REG_DSI_RESET, 0); > > > wmb(); /* controller out of reset */ > > > dsi_write(msm_host, REG_DSI_CTRL, data0); > > > -- > > > 2.17.1 > > > > > > > -- > > Sean Paul, Software Engineer, Google / Chromium OS
