linux-kernel - Re: [RFC PATCH v1 0/2]

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Date:	Wed, 1 Jun 2016 10:54:09 +0800
From:	Yakir Yang <ykk@...k-chips.com>
To:	daniel.vetter@...el.com
Cc:	Mark Yao <yzq@...k-chips.com>, Inki Dae <inki.dae@...sung.com>,
	Heiko Stuebner <heiko@...ech.de>, tfiga@...omium.org,
	Jingoo Han <jingoohan1@...il.com>,
	David Airlie <airlied@...ux.ie>,
	Thierry Reding <treding@...dia.com>, dianders@...omium.org,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	emil.l.velikov@...il.com, Dan Carpenter <dan.carpenter@...cle.com>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-samsung-soc@...r.kernel.org,
	linux-rockchip@...ts.infradead.org
Subject: Re: [RFC PATCH v1 0/2]

Hi Daniel,

On 05/31/2016 10:38 PM, Daniel Vetter wrote:
> On Tue, May 31, 2016 at 09:37:36PM +0800, Yakir Yang wrote:
>> The full name of PSR is Panel Self Refresh, panel device could refresh
>> itself with the hardware framebuffer in panel, this would make a lots
>> of sense to save the power consumption.
>>
>> For example, when desktop haven't change the context for a long time,
>> then we could refresh the data to the hardware framebuffer of panel,
>> and then let panel enter into PSR mode. After that system could poweroff
>> the LCDC controller and eDP controller, just let panel refresh the screen
>> by itself.
>>
>> It's hard to decide when panel should enter into PSR or exit from PSR, in
>> this time I chose to let the drm_vblank enable/disable event driver the PSR.
>>
>> This thread is based on Mark's RK3399 VOP thread[0] and my RK3399 eDP
>> thread[1].
>>
>> [0]: https://patchwork.kernel.org/patch/8886041/
>> [1]: https://patchwork.kernel.org/patch/9132713/
> Looks like you didn't wire up the drm_framebuffer->funcs->dirty callback
> for manual upload of simple clients like bootsplash or fbdev. I think
> that's needed. At least it's needed for every other manual upload dsi and
> edp psr implementation.
> -Daniel
That's great, thanks for your remind. Seems like userspace which does
frontbuffer rendering must call this ioctl to flush out the changes on
manual-update display outputs. It's helpful to hook this callback to
notify eDP refresh the eDP RFB(remote frame buffer).

But I think this is hard to used on Rockchip eDP controller, Rockchip eDP
driver just used two modes, Sink Device PSR_S0 (PSR inactive), and Sink
Device PSR_S2 (PSR active, display from RFB).

I think the "dirty" callback is only used when Sink device enter into PSR_S3
mode (PSR active, capture and display), need to update the remote frame
buffer. But on Rockchip platform the panel would be very easy to lose frame
in this PSR mode. I'm confused in this case, so I didn't enable that.

If we didn't enable the PSR_S3 mode, then we don't need to update the panel
remote frame buffer, so this "->dirty" callback would be unused in this 
case.

Thanks,
- Yakir
>> - Yakir
>> Thanks,
>>
>>
>> Yakir Yang (2):
>>    drm/rockchip: add a notify event about vblank enable/disable
>>    drm/rockchip: analogix: add eDP PSR function
>>
>>   drivers/gpu/drm/bridge/analogix/analogix_dp_core.c |  69 ++++++++++++++
>>   drivers/gpu/drm/bridge/analogix/analogix_dp_core.h |   5 +
>>   drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c  |  54 +++++++++++
>>   drivers/gpu/drm/bridge/analogix/analogix_dp_reg.h  |  28 ++++++
>>   drivers/gpu/drm/rockchip/Makefile                  |   2 +-
>>   drivers/gpu/drm/rockchip/analogix_dp-rockchip.c    |  65 +++++++++++++
>>   drivers/gpu/drm/rockchip/rockchip_drm_notify.c     | 105 +++++++++++++++++++++
>>   drivers/gpu/drm/rockchip/rockchip_drm_notify.h     |  33 +++++++
>>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c        |  96 +++++++++++++++++++
>>   drivers/gpu/drm/rockchip/rockchip_drm_vop.h        |   3 +
>>   drivers/gpu/drm/rockchip/rockchip_vop_reg.c        |   2 +
>>   include/drm/bridge/analogix_dp.h                   |   3 +
>>   12 files changed, 464 insertions(+), 1 deletion(-)
>>   create mode 100644 drivers/gpu/drm/rockchip/rockchip_drm_notify.c
>>   create mode 100644 drivers/gpu/drm/rockchip/rockchip_drm_notify.h
>>
>> -- 
>> 1.9.1
>>
>>