[PATCH v2 09/11] drm/exynos/hdmi: quirk for support mode timings conversion

[Andrzej Hajda]

On 17.10.2017 09:38, Inki Dae wrote:
>
> 2017년 09월 29일 19:05에 Andrzej Hajda 이(가) 쓴 글:
>> MIXER in SoCs prior to Exynos5420 supports only 4 video modes:
>> 720x480, 720x576, 1280x720, 1920x1080. Support for other modes
>> can be enabled by manipulating timings of HDMI. To do it
>> adjusted_mode should contain actual mode set on crtc.
>> With this patch it is possible to enable 1024x768 and 1280x1024
>> modes in MIXER.
>>
>> Suggested-by: Daniel Drake <drake at endlessm.com>
>> Signed-off-by: Andrzej Hajda <a.hajda at samsung.com>
>> Reviewed-by: Tobias Jakobi <tjakobi at math.uni-bielefeld.de>
>> ---
>>  drivers/gpu/drm/exynos/exynos_hdmi.c | 15 +++++++++++++--
>>  1 file changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/exynos/exynos_hdmi.c b/drivers/gpu/drm/exynos/exynos_hdmi.c
>> index 7225b6521148..4b081f6cfdcb 100644
>> --- a/drivers/gpu/drm/exynos/exynos_hdmi.c
>> +++ b/drivers/gpu/drm/exynos/exynos_hdmi.c
>> @@ -1239,6 +1239,17 @@ static void hdmi_v13_mode_apply(struct hdmi_context *hdata)
>>  static void hdmi_v14_mode_apply(struct hdmi_context *hdata)
>>  {
>>  	struct drm_display_mode *m = &hdata->encoder.crtc->state->mode;
>> +	struct drm_display_mode *am = &hdata->encoder.crtc->state->adjusted_mode;
>> +	int hquirk = 0;
>> +
>> +	/*
>> +	 * In case video mode coming from CRTC differs from requested one HDMI
>> +	 * sometimes is able to almost properly perform conversion - only
>> +	 * first line is distorted.
>> +	 */
>> +	if ((m->vdisplay != am->vdisplay) &&
>> +	    (m->hdisplay == 1280 || m->hdisplay == 1024))
>> +		hquirk = 258;
> Andrzej,
>
> The distorted value couldn't be described logically? Just I wonder why the difference happens.

Without low level documentation of the IP one could only guess what
happens there.
In case of 1024x768 one can reason as follows:
- mixer sends image in format 1280x720, so it sends 1280 - 1024 = 256
pixels too much, so if we trim it in HDMI by 256 it should display it
correctly,
- but another quirk few lines later suppress 2 pixels from
hsync_(start,end), so to balance it we should add these pixels here, so
finally we have 256 + 2 = 258.

This explanation seems quite reasonable, except it does not work for
1280x1024 mode.

Regards
Andrzej

>
> Thanks,
> Inki Dae
>
>>  
>>  	hdmi_reg_writev(hdata, HDMI_H_BLANK_0, 2, m->htotal - m->hdisplay);
>>  	hdmi_reg_writev(hdata, HDMI_V_LINE_0, 2, m->vtotal);
>> @@ -1332,8 +1343,8 @@ static void hdmi_v14_mode_apply(struct hdmi_context *hdata)
>>  	hdmi_reg_writev(hdata, HDMI_V_SYNC_LINE_AFT_PXL_6_0, 2, 0xffff);
>>  
>>  	hdmi_reg_writev(hdata, HDMI_TG_H_FSZ_L, 2, m->htotal);
>> -	hdmi_reg_writev(hdata, HDMI_TG_HACT_ST_L, 2, m->htotal - m->hdisplay);
>> -	hdmi_reg_writev(hdata, HDMI_TG_HACT_SZ_L, 2, m->hdisplay);
>> +	hdmi_reg_writev(hdata, HDMI_TG_HACT_ST_L, 2, m->htotal - m->hdisplay - hquirk);
>> +	hdmi_reg_writev(hdata, HDMI_TG_HACT_SZ_L, 2, m->hdisplay + hquirk);
>>  	hdmi_reg_writev(hdata, HDMI_TG_V_FSZ_L, 2, m->vtotal);
>>  	if (hdata->drv_data == &exynos5433_hdmi_driver_data)
>>  		hdmi_reg_writeb(hdata, HDMI_TG_DECON_EN, 1);
>>
>