linux-kernel - Re: [PATCH 1/2] drm/rockchip: dsi: hold pm-runtime across bind/unbind

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Date:   Mon, 27 Sep 2021 10:40:26 -0300
From:   Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Heiko Stübner <heiko@...ech.de>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Sandy Huang <hjc@...k-chips.com>,
        linux-rockchip@...ts.infradead.org,
        Thomas Hebb <tommyhebb@...il.com>,
        aleksandr.o.makarov@...il.com, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] drm/rockchip: dsi: hold pm-runtime across bind/unbind

On Fri, Sep 24, 2021 at 04:23:45PM -0700, Brian Norris wrote:
> In commit 59eb7193bef2, we moved most HW configuration to bind(), but we
> didn't move the runtime PM management. Therefore, depending on initial
> boot state, runtime-PM workqueue delays, and other timing factors, we
> may disable our power domain in between the hardware configuration
> (bind()) and when we enable the display. This can cause us to lose
> hardware state and fail to configure our display. For example:
> 
>   dw-mipi-dsi-rockchip ff968000.mipi: failed to write command FIFO
>   panel-innolux-p079zca ff960000.mipi.0: failed to write command 0
> 
> or:
> 
>   dw-mipi-dsi-rockchip ff968000.mipi: failed to write command FIFO
>   panel-kingdisplay-kd097d04 ff960000.mipi.0: failed write init cmds: -110
> 
> We should match the runtime PM to the lifetime of the bind()/unbind()
> cycle.
> 
> Tested on Acer Chrometab 10 (RK3399 Gru-Scarlet), with panel drivers
> built either as modules or built-in.
> 
> Side notes: it seems one is more likely to see this problem when the
> panel driver is built into the kernel. I've also seen this problem
> bisect down to commits that simply changed Kconfig dependencies, because
> it changed the order in which driver init functions were compiled into
> the kernel, and therefore the ordering and timing of built-in device
> probe.
> 
> Fixes: 59eb7193bef2 ("drm/rockchip: dsi: move all lane config except LCDC mux to bind()")
> Link: https://lore.kernel.org/linux-rockchip/9aedfb528600ecf871885f7293ca4207c84d16c1.camel@gmail.com/
> Reported-by: <aleksandr.o.makarov@...il.com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Brian Norris <briannorris@...omium.org>
> ---

This fixes the display enablement issue in Acer Chrometab 10 (RK3399
Gru-Scarlet) indeed.

Tested-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

Thanks,
Nícolas