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

From: Inki Dae <inki.dae@samsung.com>
To: Andrzej Hajda <a.hajda@samsung.com>
Cc: linux-samsung-soc@vger.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	dri-devel@lists.freedesktop.org,
	Daniel Drake <drake@endlessm.com>,
	Tobias Jakobi <tjakobi@math.uni-bielefeld.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH v2 09/11] drm/exynos/hdmi: quirk for support mode timings conversion
Date: Wed, 18 Oct 2017 11:31:55 +0900	[thread overview]
Message-ID: <59E6BD1B.6030201@samsung.com> (raw)
In-Reply-To: <8201fc31-1070-1971-558b-dce0c952e142@samsung.com>

2017년 10월 17일 17:04에 Andrzej Hajda 이(가) 쓴 글:
> 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@endlessm.com>
>>> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
>>> Reviewed-by: Tobias Jakobi <tjakobi@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.

We aren't sure 100% but above comment would be helpful to other developers. So could you leave the comment?

Thanks,
Inki Dae

> 
> 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);
>>>
>>
> 
> 
> 
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