Re: [PATCH] drm/i915/dsi: Use owned panel/backlight GPIOs in VLV MIPI sequences

[Bartosz Golaszewski]

On Mon, 19 Oct 2026 13:18:50 +0200, Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> said:
> +Cc: Bart (as GPIOLIB maintainer and author of the reset-gpio rework).
>
> On Mon, Oct 19, 2026 at 07:03:57AM -0400, Michael Anderson wrote:
>> Thanks for looking at this. I'd like to make sure I understand before
>> doing a v2.
>>
>> Here both users of pin 10 are i915 itself: intel_dsi_vbt_gpio_init()
>> takes it as the "backlight" enable GPIO (soc_panel_gpio_table,
>> PPS_BLC_SOC), and the VBT MIPI sequences on this tablet then toggle the
>> same pin as the panel reset (low in ASSERT_RESET, high-low-high in
>> DEASSERT_RESET). Do you mean describing pin 10 with a software-node
>> "reset-gpios" reference and having both paths go through
>> reset_control_*(), or something else?
>>
>> One concern: the VBT drives explicit pulses on the pin, and shared reset
>> controls are refcounted, so a pulse from one path wouldn't reach the line
>> while the other holds it deasserted. Would an exclusive reset obtained
>> once by i915 and used by both paths work instead, or am I missing how
>> reset-gpio handles this?
>
> But then it sounds like the request-by-demand?
> Bart, any ideas how to address this case?
>

Yeah. If you need a more complex sequence than what refcounted reset-gpio or
gpio-shared-proxy can provide (for instance a timed pulse) then you probably
need to look at implementing a power sequencer using drivers/power/sequencing/.

Bart