linux-kernel - Re: [PATCH] drm/exynos: don't use HW trigger for Exynos5420/5422/5800

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Date:	Fri, 10 Jun 2016 07:35:30 +0900
From:	Inki Dae <inki.dae@...sung.com>
To:	Javier Martinez Canillas <javier@....samsung.com>,
	linux-kernel@...r.kernel.org
Cc:	Marc Zyngier <marc.zyngier@....com>, Kukjin Kim <kgene@...nel.org>,
	Seung-Woo Kim <sw0312.kim@...sung.com>,
	dri-devel@...ts.freedesktop.org, linux-samsung-soc@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	David Airlie <airlied@...ux.ie>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] drm/exynos: don't use HW trigger for Exynos5420/5422/5800

Hi Javier,

2016년 06월 09일 09:17에 Javier Martinez Canillas 이(가) 쓴 글:
> Hello Inki,
> 
> Thanks for your feedback.
> 
> On 06/08/2016 07:09 PM, Inki Dae wrote:
>> Hi Javier,
>>
>> 2016년 06월 02일 23:20에 Javier Martinez Canillas 이(가) 쓴 글:
>>> Commit a6f75aa161c5 ("drm/exynos: fimd: add HW trigger support") added
>>> hardware trigger support to the FIMD controller driver. But this broke
>>> the display in at least the Exynos5800 Peach Pi Chromebook.
>>>
>>> So until the issue is fixed, avoid using HW trigger for the Exynos5420
>>> based boards and use SW trigger as it was before the mentioned commit.
>>>
>>> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
>>>
>>> ---
>>>
>>> Hello Inki,
>>>
>>> Since commit a6f75aa161c5 landed in v4.7-rc1, I think $SUBJECT should be
>>> picked to make sure that v4.7 is released with the display working for
>>> the Exynos5420 based Chromebooks.
>>>
>>> We can then figure out what's wrong with the HW trigger support and fix
>>> it for v4.8.
>>
>> Agree. And below is a trivial comment.
>>
> 
> I'm glad that you agree.
> 
>>>
>>> Best regards,
>>> Javier
>>>
>>>  drivers/gpu/drm/exynos/exynos_drm_fimd.c | 3 ---
>>>  1 file changed, 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
>>> index 1c23a8ff5e83..f10030ff00e6 100644
>>> --- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
>>> +++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
>>> @@ -170,14 +170,11 @@ static struct fimd_driver_data exynos5420_fimd_driver_data = {
>>>  	.lcdblk_vt_shift = 24,
>>>  	.lcdblk_bypass_shift = 15,
>>>  	.lcdblk_mic_bypass_shift = 11,
>>> -	.trg_type = I80_HW_TRG,
>>>  	.has_shadowcon = 1,
>>>  	.has_vidoutcon = 1,
>>>  	.has_vtsel = 1,
>>>  	.has_mic_bypass = 1,
>>>  	.has_dp_clk = 1,
>>> -	.has_hw_trigger = 1,
>>> -	.has_trigger_per_te = 1,
>>
>> We don't need to remove above two lines. It would be enough to remove 'trg_type = I80_HW_TRG', which makes FIMD to be worked with SW trigger in default.
>>
> 
> I know that removing .trg_type is enough but I also removed those lines
> because the fields are not used if .trg_type != I80_HW_TRG. So there is
> no point to leave a set for unused fields.
> 
> We can latter add those one HW trigger support is fixed for Exynos5420.
> 

As of now, I can merge it but I think it would be not reasonable solution because potential problem still exists even we use SW trigger mode in default - ie., in case of using HW trigger mode at bootloader, same problem would happen as long as we don't support PSR mode support.

Thanks,
Inki Dae

>> Thanks,
>> Inki Dae
>>
>>>  };
>>>  
>>>  struct fimd_context {
>>>
>> --
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>>
> 
> Best regards,
>