linux-kernel - Re: [PATCH 0/3] drm/panel: jh057n00900: Move dsi init sequence to prepare

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Date:   Fri, 26 Jul 2019 15:16:11 +0200
From:   Guido Günther <guido.gunther@...i.sm>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Purism Kernel Team <kernel@...i.sm>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] drm/panel: jh057n00900: Move dsi init sequence to
 prepare

Hi Sam,
On Fri, Jul 26, 2019 at 12:25:29PM +0200, Sam Ravnborg wrote:
> Hi Guido.
> 
> On Fri, Jul 26, 2019 at 11:21:40AM +0200, Guido Günther wrote:
> > If the panel is wrapped in a panel_bridge it gets prepar()ed before the
> > upstream DSI bridge which can cause hangs (e.g. with imx-nwl since clocks
> > are not enabled yet). To avoid this move the panel's first DSI access to
> > enable() so the upstream bridge can prepare the DSI host controller in
> > it's pre_enable().
> > 
> > The second patch makes the disable() call symmetric to the above and the third
> > one just eases debugging.
> > 
> > Guido Günther (3):
> >   drm/panel: jh057n00900: Move panel DSI init to enable()
> >   drm/panel: jh057n00900: Move mipi_dsi_dcs_set_display_off to disable()
> >   drm/panel: jh057n00900: Print error code on all DRM_DEV_ERROR()s
> 
> Patch 1 + 3 are both:
> Reviewed-by: Sam Ravnborg <sam@...nborg.org>
> 
> See comment on patch 2.

Fixed in v2.

> 
> While you are touching this driver can you make an extra patch?
> 
> Today the driver calls the internal prepare,enable,disable,unprepare
> functions.
> The right way to do it is to use the
> drm_panel_(prepare,enable,disable,unprepare) variants.

I hope I got this right in v2 but...

> 
> The benefit is that we can move a little logic to these functions
> and the drivers will then benefit from this.
> 
> Two things I have in my local queue:
> - Move bool for prepared/enabled
>   (to protect that we do not prepare/enable twice)
> - backlight support

...i hope so since what you have planned here would eliminate lots of
code duplication in the panel drivers.
Cheers and thanks for having a look!
 -- Guido

> 
> This driver will benefit form both and this little modification will
> make it simpler to introduce.
> I can also prepare the patch if you prefer.
> 
> 	Sam
>