linux-kernel - Re: [PATCH v2 05/10] media: adv748x: add support for HDMI audio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 20 Mar 2020 12:11:57 +0100
From:   Alex Riesen <alexander.riesen@...itec.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Kieran Bingham <kieran.bingham@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        "Laurent Pinchart" <laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        driverdevel <devel@...verdev.osuosl.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v2 05/10] media: adv748x: add support for HDMI audio

Hi Geert,

Geert Uytterhoeven, Fri, Mar 20, 2020 12:05:20 +0100:
> On Fri, Mar 20, 2020 at 11:58 AM Alex Riesen <alexander.riesen@...itec.com> wrote:
> > Geert Uytterhoeven, Fri, Mar 20, 2020 09:43:29 +0100:
> > > On Thu, Mar 19, 2020 at 6:42 PM Alex Riesen <alexander.riesen@...itec.com> wrote:
> > > > This adds an implemention of SoC DAI driver which provides access to the
> > > > I2S port of the device.
> >
> > I just noticed I don't do clk_prepare_enable anywhere.
> > Shouldn't the clock master enable its clocks somewhere?
> 
> Usually the consumer is responsible for doing that.
> Does the rcar-sound driver do that?

No, it does not (verified by /sys/kernel/debug/clk/clk_summary during
transfer).

> But in this case, perhaps the clock should be enabled implicitly in response
> to a request from the audio subsystem, like you do below.

Ok...

> Note that you register a fixed-rate clock, which is assumed to be always
> enabled. Perhaps a gateable clock type is more appropriate?

The gated clock implementation requires use of an I/O register, which I don't
have in this case (an I2C connected device).

I considered implementing full clk_hw set of operations, but decided against
it: it's a lot for this simple configuration. Few other drivers do that, too.

Regards,
Alex