linux-kernel - Re: [PATCH v3 9/9] drm/panel: innolux-p079zca: Don't use a table for initting panels

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Date: Fri, 3 May 2024 09:32:48 -0700
From: Doug Anderson <dianders@...omium.org>
To: dri-devel@...ts.freedesktop.org
Cc: Linus Walleij <linus.walleij@...aro.org>, Jani Nikula <jani.nikula@...ux.intel.com>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
	Cong Yang <yangcong5@...qin.corp-partner.google.com>, Hsin-Yi Wang <hsinyi@...gle.com>, 
	Brian Norris <briannorris@...omium.org>, Sam Ravnborg <sam@...nborg.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Javier Martinez Canillas <javierm@...hat.com>, 
	Joel Selvaraj <jo@...amily.in>, lvzhaoxiong@...qin.corp-partner.google.com, 
	Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>, 
	Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 9/9] drm/panel: innolux-p079zca: Don't use a table for
 initting panels

Hi,

On Wed, May 1, 2024 at 8:43 AM Douglas Anderson <dianders@...omium.org> wrote:
>
> @@ -132,33 +125,9 @@ static int innolux_panel_prepare(struct drm_panel *panel)
>         /* p079zca: t4, p097pfg: t5 */
>         usleep_range(20000, 21000);
>
> -       if (innolux->desc->init_cmds) {
> -               const struct panel_init_cmd *cmds =
> -                                       innolux->desc->init_cmds;
> -               unsigned int i;
> -
> -               for (i = 0; cmds[i].len != 0; i++) {
> -                       const struct panel_init_cmd *cmd = &cmds[i];
> -
> -                       err = mipi_dsi_generic_write(innolux->link, cmd->data,
> -                                                    cmd->len);
> -                       if (err < 0) {
> -                               dev_err(panel->dev, "failed to write command %u\n", i);
> -                               goto poweroff;
> -                       }
> -
> -                       /*
> -                        * Included by random guessing, because without this
> -                        * (or at least, some delay), the panel sometimes
> -                        * didn't appear to pick up the command sequence.
> -                        */
> -                       err = mipi_dsi_dcs_nop(innolux->link);
> -                       if (err < 0) {
> -                               dev_err(panel->dev, "failed to send DCS nop: %d\n", err);
> -                               goto poweroff;
> -                       }
> -               }
> -       }
> +       err = innolux->desc->init(innolux);
> +       if (err < 0)
> +               goto poweroff;

FWIW, I happened to notice a bug in the above by code inspection. The
old code checked "if (innolux->desc->init_cmds)" and thus handled
init_cmds being NULL. The new code doesn't handle the init function
being NULL. One of the two panels in this file (which seems to have no
users in mainline) doesn't specify an init sequence.

I'll spin this next week with the extra "if" test.

-Doug