[Intel-gfx] [PATCH 1/2] drm/i915/dsi: Fix swapping of MIPI_SEQ_DEASSERT_RESET / MIPI_SEQ_ASSERT_RESET

[Hans de Goede]

Hi,

On 29-11-16 14:06, Hans de Goede wrote:

<Snip>

> p.s.
>
> I'm also trying to come up with some patches which properly
> integrate pwm-lpss with the i915 driver instead of it
> throwing a "Failed to own the pwm chip" error. But as soon
> as I hook up things so that pwm_get() returns the pwm-lpss
> pwm0 I hit:
>
> https://bugs.freedesktop.org/show_bug.cgi?id=97330
>
> I get the same pipe-a stuck (or not seeing vblank irqs?)
> problems sometimes without the pwm-lpss driver in the loop
> but then only sometimes and with pwm-lpss I get this
> problem when loading the i915 driver most of the time
> (but not all the time).
>
> I've been debugging this a couple of evenings in a row
> now, but no luck sofar.

Ok, a couple of more evenings of debugging + working on
this today has finally resulted in me finding a fix :)

The problem is that on driver load we call
chv_pipe_power_well_ops.enable() which calls
vlv_init_display_clock_gating() which clears
the DPOUNIT_CLOCK_GATE_DISABLE bit in DSPCLK_GATE_D
while the DSI panel is being driven by PIPE-A, as
already documented in intel_dsi_pre_enable()
allowing the DPOUNIT to get gated while DSI
active will result in a stuck PIPE-A.

I've written a patch for this, I'll send this
right after this mail, and attach it to bug:
https://bugs.freedesktop.org/show_bug.cgi?id=97330

Which I believe is the same issue.

Regards,

Hans