Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
References: <20230320161636.24411-1-romanberanek@icloud.com>
 <87wn356ni4.fsf@oltmanns.dev> <20230327202045.ceeqqwjug4ktxtsf@penduick>
 <CRHKFX934UA0.1MCKCD8SJSPIE@iMac.local>
 <20230329195802.veybo3367zifw77n@penduick>
From:   Frank Oltmanns <frank@oltmanns.dev>
To:     Roman Beranek <romanberanek@icloud.com>
Cc:     Maxime Ripard <maxime@cerno.tech>, Chen-Yu Tsai <wens@csie.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/sun4i: uncouple DSI dotclock divider from
 TCON0_DCLK_REG
Date:   Thu, 30 Mar 2023 06:45:22 +0200
In-reply-to: <20230329195802.veybo3367zifw77n@penduick>
Message-ID: <877cuyon5e.fsf@oltmanns.dev>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Hi Roman,

On 2023-03-29 at 21:58:02 +0200, Maxime Ripard <maxime@cerno.tech> wrote:
> On Tue, Mar 28, 2023 at 01:48:33AM +0200, Roman Beranek wrote:
>> On Mon Mar 27, 2023 at 10:20 PM CEST, Maxime Ripard wrote:
>> >
>> > On Sat, Mar 25, 2023 at 12:40:04PM +0100, Frank Oltmanns wrote:
>> > > Claiming to set the divider to a different value (bpp / lanes) than =
what we=E2=80=99re actually using in
>> > > the end (SUN6I_DSIO_TCON_DIV) is somehow bugging me. I feel like the=
 proposal that I submitted is
>> > > more direct: <https://lore.kernel.org/all/20230319160704.9858-2-fran=
k@oltmanns.dev/>
>> >
>> > Yeah, this patch looks better to me too: it's simpler, more straightfo=
rward. If Roman can confirm it
>> > works with his testing, I'll be happy to merge it.
>> >
>>
>> So I've just found out that my understanding of what sun4i_dotclock is
>> was wrong the whole time. I treated it as a virtual clock representing
>> the true CRTC pixel clock and only coincidentally also matching what
>> A64 Reference Manual labels as TCON0 data clock (a coincidence to which
>> DSI is an exception).
>>
>> Now that I finally see dotclock as 'what could dclk be an abbreviation
>> to', I to agree that it's not only straightforward but also correct to
>> keep the divider at 4 and adjust the rate as is done it the patch Frank
>> submitted.
>>
>> In order to preserve semantic correctness however, I propose to preface
>> the change with a patch that renames sun4i_dotclock and tcon-pixel-clock
>> such that dot/pixel is replaced with d/data. What do you think?
>
> I don't think it's exposed to the userspace in any way so it makes sense =
to me

Roman, will you please submit a V2 of the patch I submitted then? Or do
you want me to do it?

Thanks,
  Frank

>
> Maxime
>


--