Re: [PATCH] drm/rockchip: vop2: Drop unused if_dclk_rate variable

From: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
To: "Heiko Stübner" <heiko@sntech.de>,
	"Sandy Huang" <hjc@rock-chips.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Andy Yan" <andy.yan@rock-chips.com>
Cc: dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org,
	kernel@collabora.com
Subject: Re: [PATCH] drm/rockchip: vop2: Drop unused if_dclk_rate variable
Date: Fri, 5 Jan 2024 19:49:14 +0200	[thread overview]
Message-ID: <30114fa6-d83d-4563-9f3b-2975ddfd2752@collabora.com> (raw)
In-Reply-To: <13141620.VsHLxoZxqI@diego>

On 1/5/24 11:57, Heiko Stübner wrote:
> Hi,
> 
> Am Freitag, 5. Januar 2024, 10:04:55 CET schrieb Andy Yan:
>> On 1/4/24 23:58, Heiko Stübner wrote:
>>> Am Donnerstag, 4. Januar 2024, 15:39:50 CET schrieb Cristian Ciocaltea:
>>>> Commit 5a028e8f062f ("drm/rockchip: vop2: Add support for rk3588")
>>>> introduced a variable which ended up being unused.  Remove it.
>>>>
>>>> rockchip_drm_vop2.c:1688:23: warning: variable ‘if_dclk_rate’ set but not used [-Wunused-but-set-variable]
>>>>
>>>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

[...]

>>> with the code continuing with those static constants but the comment
>>> showing a forumula, I do hope Andy can provide a bit of insight into
>>> what is happening here.
>>>
>>> I.e. I'd really like to understand if that really is just a remnant or
>>> something different is needed.
>>
>> This is not a remnant, in my V1, I calculate all the div by formula, but Sascha prefer
>> more for a constants value[0], so I keep this formula as comments to indicate how these value come from.
>>
>> [0]https://patchwork.kernel.org/project/linux-rockchip/patch/20231114112855.1771372-1-andyshrk@163.com/
> 
> thanks for referencing the source of the change.
> Leaving the formula in there was the right choice I think
> 
> That still leaves the issue with the "unused" warning.
> 
> @Christan: in the hdmi block itself can you move the 
> 	if_dclk_rate = dclk_core_rate / K;
> to the comment block please? And possibly reference the use
> of the static values in the comment message.
> 
> The if_dclk_rate var declaration at the top of the function can of course
> go away.
> 
> That way we still keep documenting how these values came to be:

Requested changes submitted via v2:

https://lore.kernel.org/lkml/20240105174007.98054-1-cristian.ciocaltea@collabora.com/

Thanks,
Cristian

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