[Bug 108826] [GLK DSI] Black screen after grub - Ubuntu 18.04 - kernel latest tip 21.11.2018

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108826

--- Comment #119 from Stanislav Lisovskiy <stanislav.lisovskiy at intel.com> ---
(In reply to Mark Wynn Garcia from comment #118)
> Hello Stanislav. It's very good to know you're considering looking into the
> Windows driver sources. This will definitely speed things up. :D
> 
> Could you please share with us a patch of your hack? I want to try it on my
> device (D330), and looking into the VBT it seems it does touch GPIO index 3
> on MIPI_SEQ_POWER_ON, though there's no sequence with GPIO index 6.

GPIO index 6 is the reset:

BDB block 53 - MIPI sequence block:
        Sequence block version v3
        Sequence 1 - MIPI_SEQ_ASSERT_RESET
                GPIO index 6, number 135, set 1 (0x01)
                Delay: 12000 us
                GPIO index 6, number 135, set 0 (0x00)
                Delay: 5000 us
                GPIO index 6, number 135, set 1 (0x01)
        Sequence 3 - MIPI_SEQ_DISPLAY_ON
                Send DCS: Port A, VC 0, LP, Type 05, Length 1, Data 11
                Send DCS: Port A, VC 0, LP, Type 15, Length 2, Data b0 5a
                Send DCS: Port A, VC 0, LP, Type 15, Length 2, Data b1 02
                Send DCS: Port A, VC 0, LP, Type 15, Length 2, Data 39 49
                Send DCS: Port A, VC 0, LP, Type 05, Length 1, Data 29
        Sequence 4 - MIPI_SEQ_DISPLAY_OFF
                Send DCS: Port A, VC 0, LP, Type 05, Length 1, Data 28
                Delay: 120000 us
                Send DCS: Port A, VC 0, LP, Type 05, Length 1, Data 10
                Delay: 34000 us
        Sequence 5 - MIPI_SEQ_DEASSERT_RESET
                Delay: 10000 us
                GPIO index 6, number 135, set 0 (0x00)
        Sequence 6 - MIPI_SEQ_BACKLIGHT_ON
                GPIO index 4, number 145, set 1 (0x01)
                Delay: 2000 us
        Sequence 7 - MIPI_SEQ_BACKLIGHT_OFF
                GPIO index 4, number 145, set 0 (0x00)
                Delay: 1000 us
        Sequence 10 - MIPI_SEQ_POWER_ON
                GPIO index 3, number 144, set 1 (0x01)
                Delay: 5000 us
        Sequence 11 - MIPI_SEQ_POWER_OFF
                GPIO index 3, number 144, set 0 (0x00)

The hack is as simple as doing something like this:

git diff intel_dsi_vbt.c 
diff --git a/drivers/gpu/drm/i915/intel_dsi_vbt.c
b/drivers/gpu/drm/i915/intel_dsi_vbt.c
index fbed9064ac7e..f9a2e351184f 100644
--- a/drivers/gpu/drm/i915/intel_dsi_vbt.c
+++ b/drivers/gpu/drm/i915/intel_dsi_vbt.c
@@ -324,6 +324,9 @@ static void bxt_exec_gpio(struct drm_i915_private
*dev_priv,
        struct gpio_desc *gpio_desc = bxt_gpio_table[gpio_index];

        if (!gpio_desc) {
+               if (gpio_index == 3 || gpio_index == 6) {
+                       return;
+               }
                gpio_desc = devm_gpiod_get_index(dev_priv->drm.dev,
                                                 NULL, gpio_index,
                                                 value ? GPIOD_OUT_LOW :

Which is of course quite symptomatic treatment and suspend fails to recover
still..

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