[Bug 101205] [i915][BYT] Blank screen on MIPI panel

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101205

--- Comment #5 from Innocent Bystander <dimitry at cos.flag.org> ---
Sprinkling a few printks in the kernel I've discovered that in the file
`intel_bios.c` inside the function `parse_mipi_sequence()` a call to
`find_panel_sequence_block()` here:

https://cgit.freedesktop.org/drm/drm-tip/tree/drivers/gpu/drm/i915/intel_bios.c#n984

returns 2-byte long sequence block with the the first seq_id set to 0
(MIPI_SEQ_END).

This causes `intel_dsi_vbt_exec_sequence()` in `intel_dsi_vbt.c` to simply
return here:

https://cgit.freedesktop.org/drm/drm-tip/tree/drivers/gpu/drm/i915/intel_dsi_vbt.c#n429

I am really just shooting in the dark here, as I've no clue what all of this
means. My guess is these are some sort of initialization sequences for the MIPI
panel.

On the other hand, on the working unit the size of the sequence block is 1350
and it contains seq_ids: 1, 5, 2, 3 and 4, which would be
MIPI_SEQ_{DEASSERT_RESET,ASSERT_RESET,INIT_OTP,DISPLAY_ON,DISPLAY_OFF}.

If somebody could point me in the right direction, I would very much appreciate
that.

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