Re: [PATCH 33/33] drm/panel-simple: Fix dotclock for LG ACX467AKM-7

Jonathan Marek
2020-03-03T08:25:05Z

On 3/2/20 10:13 PM, Brian Masney wrote:
> On Mon, Mar 02, 2020 at 03:48:22PM -0500, Jonathan Marek wrote:
>> Hi,
>>
>> This is a command mode panel and the the msm/mdp5 driver uses the vrefresh
>> field for the actual refresh rate, while the dotclock field is used for the
>> DSI clocks. The dotclock needed to be a bit higher than necessary otherwise
>> the panel would not work.
>>
>> If you want to get rid of the separate clock/vrefresh fields there would
>> need to be some changes to msm driver.
>>
>> (note I hadn't made the patch with upstreaming in mind, the 150000 value is
>> likely not optimal, just something that worked, this is something that
>> should have been checked with the downstream driver)
>
> Is this the right clock frequency in the downstream MSM 3.4 kernel that
> you're talking about?
>
> https://github.com/AICP/kernel_lge_hammerhead/blob/n7.1/arch/arm/mach-msm/clock-8974.c#L3326
>

No, I'm talking about the DSI clock (the driver for it is in
drm/msm/dsi/). For a command mode panel the front/back porches aren't
relevant, but the dsi pixel/byte clock need to be a bit higher than
1920x1080x60. Since 125498 is a little higher than 124416 that might be
enough (there is also rounding of the clock values to consider).

> I don't see any obvious clock values in the downstream command mode
> panel configuration:
>
> https://github.com/AICP/kernel_lge_hammerhead/blob/n7.1/arch/arm/boot/dts/msm8974-hammerhead/msm8974-hammerhead-panel.dtsi#L591
>
> Anyways, I tried Ville's patch with the framebuffer, kmscube, and X11
> and everything appears to be working fine. You can add my Tested-by if
> you end up applying this.
>
> Tested-by: Brian Masney <masneyb@onstation.org>
>
> Brian
>
>
>> On 3/2/20 3:34 PM, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>>
>>> The currently listed dotclock disagrees with the currently
>>> listed vrefresh rate. Change the dotclock to match the vrefresh.
>>>
>>> Someone tell me which (if either) of the dotclock or vreresh is
>>> correct?
>>>
>>> Cc: Jonathan Marek <jonathan@marek.ca>
>>> Cc: Brian Masney <masneyb@onstation.org>
>>> Cc: Linus Walleij <linus.walleij@linaro.org>
>>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> ---
>>> drivers/gpu/drm/panel/panel-simple.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
>>> index b24fdf239440..f958d8dfd760 100644
>>> --- a/drivers/gpu/drm/panel/panel-simple.c
>>> +++ b/drivers/gpu/drm/panel/panel-simple.c
>>> @@ -3996,7 +3996,7 @@ static const struct panel_desc_dsi panasonic_vvx10f004b00 = {
>>> };
>>> static const struct drm_display_mode lg_acx467akm_7_mode = {
>>> - .clock = 150000,
>>> + .clock = 125498,
>>> .hdisplay = 1080,
>>> .hsync_start = 1080 + 2,
>>> .hsync_end = 1080 + 2 + 2,
>>>