linux-kernel - Re: [PATCH v2 0/5] drm: rockchip: various ports for older VOPs

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Date:   Sat, 25 Jul 2020 15:52:34 +0200
From:   Alex Bee <knaerzche@...il.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/5] drm: rockchip: various ports for older VOPs


Am 22.07.20 um 23:43 schrieb Daniel Vetter:
> On Wed, Jul 22, 2020 at 8:13 PM Alex Bee <knaerzche@...il.com> wrote:
>> Hi,
>>
>> this series mainly ports existining functionality to older SoCs - most
>> importantly enables alpha blending for RK3036, RK3066, RK3126 and
>> RK3188.
>> Besides that, it also changes the window type from DRM_PLANE_TYPE_CURSOR
>> to DRM_PLANE_TYPE_OVERLAY for VOPs that have only one (1) overlay window.
> This doesn't make much sense, the cursor overlay is really just a hint
> for legacy ioctls that this is the overlay that should be used for
> cursors. Compositors should try to use such planes as full overlays
> (if they don't want to use them as a cursor). So sounds like a case of
> "fix your compositor".
I agree here - but: If HWC windows would have been implemented in this 
particular driver, their max size would be 128x128 on some SoCs - so 
they woudn't be really suitable to create an OSD overlay at 4K, for 
example. I don't know, but I guess other vendors implement their HWC 
windows on this reduced HW resources as well. I guess that is one of the 
reasons, why userspace, which aims to be cross-plattfrom, avoids 
DRM_PLANE_TYPE_CURSOR when its looking for an usable overlay plane. (a 
heuristic, indeed)
> For atomic there's 0 difference between a overlay or a cursor (primary
> plane is still treated somewhat special in the RMFB ioctl, but again
> that's for backwards compat reasons with existing uapi, not because
> the primary plane is different).
>
> What does happen though is that this breaks cursor for legacy
> userspace, which is probably not really what you want.

Indeed not.

Beforhand I was submiiting this, I looked arround and couldn't find 
anything which relies or even depends of a cursor window to be 
available. Even if: as per spec only one DRM_PLANE_TYPE_PRIMARY is 
mandatory, everything else is optional.

> -Daniel
>
>
>> Regards,
>> Alex
>>
>> Changes in v2:
>> - drop not yet upstreamed dsp_data_swap from RK3188 regs
>> - rephrase most commit messages
>>
>> Alex Bee (5):
>>    drm: rockchip: add scaling for RK3036 win1
>>    drm: rockchip: add missing registers for RK3188
>>    drm: rockchip: add alpha support for RK3036, RK3066, RK3126 and RK3188
>>    drm: rockchip: set alpha_en to 0 if it is not used
>>    drm: rockchip: use overlay windows as such
>>
>>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c |  1 +
>>   drivers/gpu/drm/rockchip/rockchip_vop_reg.c | 42 ++++++++++++++++++---
>>   drivers/gpu/drm/rockchip/rockchip_vop_reg.h |  1 +
>>   3 files changed, 38 insertions(+), 6 deletions(-)
>>
>> --
>> 2.17.1
>>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

Best Regards