linux-kernel - Re: [PATCH] media: rkvdec: Switch to using structs instead of writel

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Message-ID: <a787e6e0-d4ce-45e3-8263-2489585d3ec0@kwiboo.se>
Date: Tue, 27 May 2025 19:51:31 +0200
From: Jonas Karlman <jonas@...boo.se>
To: Detlev Casanova <detlev.casanova@...labora.com>
Cc: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
 "linux-rockchip@...ts.infradead.org" <linux-rockchip@...ts.infradead.org>,
 "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
 "kernel@...labora.com" <kernel@...labora.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: rkvdec: Switch to using structs instead of writel

Hi Detlev,

On 2025-05-27 17:00, Detlev Casanova wrote:
> In an effort to merge the rkvdec2 driver [1] with this one, switch from
> writel() calls to using structs to represent the register mappings.

Please wait with this until HEVC support has landed, now that H264
4:2:2/Hi10 finally have been merged I was hoping to be able to send a v2
of the old HEVC series [3]. I was waiting on v6.16-rc1 before sending
the series but can send it sooner if needed, [4] has current state of v2.

H264 4:2:2/Hi10 and HEVC have been in the works for a few years now,
would be nice to have it fully land before refactoring starts ;-)

[3] https://lore.kernel.org/linux-media/20231105233630.3927502-1-jonas@kwiboo.se
[4] https://github.com/Kwiboo/linux-rockchip/commits/linuxtv-rkvdec-hevc-v2b/

> This is done in order to have all supported decoders use the same format
> in the future and ease reading of the code.

Do you have any work-in-progress patches for this?

> Using structs also improves stability as the hardware is tested and
> validated downstream using a similar method.
> It was noticed, on decoders, that:
>  - Some registers require to be writen in increasing order [2]
>  - Some registers, even if unrelated, need to be written to their reset
>    values (it was the case here for axi_ddr_[rw]data).
> 
> Using structs can also help improving performance later when, e.g.
> multicore support is added on RK3588.

Are your referring to the linked-list feature (also present in e.g.
RK3328) or just for multi-core purpose?

Regards,
Jonas

> Performance seems to be slightly improved, but at least, not made worse.
> Running fluster's JVT-AVC_V1 test suite with GStreamer on the Radxa ROCK
> PI 4 SE gives the following times:
> 
> Before this patch:
> 
> - --jobs 1: Ran 129/135 tests successfully               in 77.167 secs
> - --jobs 6: Ran 129/135 tests successfully               in 23.046 secs
> 
> With this patch:
> - --jobs 1: Ran 129/135 tests successfully               in 70.698 secs
> - --jobs 6: Ran 129/135 tests successfully               in 22.917 secs
> 
> This also shows that the fluster score hasn't changed.
> 
> [1]: https://lore.kernel.org/all/20250325213303.826925-1-detlev.casanova@collabora.com/
> [2]: https://lore.kernel.org/all/20200127143009.15677-5-andrzej.p@collabora.com/
> 
> Signed-off-by: Detlev Casanova <detlev.casanova@...labora.com>
> ---
>  drivers/staging/media/rkvdec/rkvdec-h264.c | 168 +++---
>  drivers/staging/media/rkvdec/rkvdec-regs.h | 567 ++++++++++++++-------
>  drivers/staging/media/rkvdec/rkvdec-vp9.c  | 239 ++++-----
>  drivers/staging/media/rkvdec/rkvdec.c      |   1 -
>  4 files changed, 559 insertions(+), 416 deletions(-)

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