linux-kernel - Re: [PATCH v2 2/2] media: i2c: add support for ov4689

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Date:   Thu, 22 Sep 2022 20:39:48 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Mikhail Rudenko <mike.rudenko@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Shawn Tu <shawnx.tu@...el.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Daniel Scally <djrscally@...il.com>,
        Christian Hemp <c.hemp@...tec.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Marek Vasut <marex@...x.de>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] media: i2c: add support for ov4689

Hi Mikhail,

On Thu, Sep 22, 2022 at 06:23:05PM +0300, Mikhail Rudenko wrote:
> 
> Hi Sakari,
> 
> and thanks for reviewing this!

You're welcome!

> 
> Please see my comments below:
> 
> On 2022-09-22 at 09:53 GMT, Sakari Ailus <sakari.ailus@...ux.intel.com> wrote:
...
> >> +static inline u32 ov4689_cal_delay(u32 cycles)
> >> +{
> >> +	return DIV_ROUND_UP(cycles, OV4689_XVCLK_FREQ / 1000 / 1000);
> >
> > Please use the actual rate instead.
> >
> 
> Do you mean clk_get_rate(ov4689->xvclk), right? What if we have an ACPI

Yes.

> system and xvclk is NULL here? Please explain.

There are a few ways this could work on ACPI based systems but generally
you'd have "clock-frequency" property to indicate the frequency even if
clocks themselves wouldn't be available (when controlled via ACPI)).

-- 
Kind regards,

Sakari Ailus