Re: [PATCH 04/33] drm/panel-ilitek-ili9322: Fix dotclocks

Linus Walleij
2020-03-07T14:39:05Z

Hi Ville!

On Mon, Mar 2, 2020 at 9:35 PM Ville Syrjala
<ville.syrjala@linux.intel.com> wrote:

> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The currently listed dotclocks disagree with the currently
> listed vrefresh rates. Change the dotclocks to match the vrefresh.
>
> Someone tell me which (if either) of the dotclock or vreresh is
> correct?
>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Thierry Reding <treding@nvidia.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

This display is particularly peculiar since it uses
the ITU-T packed streams and like DSI those have
a different clocking than whatever is clocked out to the
actual display by the pixel clock.

Datasheet is here:
https://dflund.se/~triad/krad/dlink-dir-685/ILI9322DS_V1.12.pdf

I see I have consistently set the clocks two orders of
magnitude wrong in this driver, mea culpa :P
But I checked them all and what I think you should
do is just divide them all by 100 and leave as-is.

> /* Serial RGB modes */
> static const struct drm_display_mode srgb_320x240_mode = {
> - .clock = 2453500,
> + .clock = 14478,

Please set to 24535.

> static const struct drm_display_mode srgb_360x240_mode = {
> - .clock = 2700000,
> + .clock = 10014,

Please set to 27000.

> /* This is the only mode listed for parallel RGB in the datasheet */
> static const struct drm_display_mode prgb_320x240_mode = {
> - .clock = 6400000,
> + .clock = 6429,

Please set to 64000.

> static const struct drm_display_mode yuv_640x320_mode = {
> - .clock = 2454000,
> + .clock = 18954,

Please set to 24540.

> static const struct drm_display_mode yuv_720x360_mode = {
> - .clock = 2700000,
> + .clock = 22911,

Please set to 27000.

> /* BT.656 VGA mode, 640x480 */
> static const struct drm_display_mode itu_r_bt_656_640_mode = {
> - .clock = 2454000,
> + .clock = 27480,

Please set to 24540.

> /* BT.656 D1 mode 720x480 */
> static const struct drm_display_mode itu_r_bt_656_720_mode = {
> - .clock = 2700000,
> + .clock = 29880,

Please set to 27000.

Yours,
Linus Walleij