From: Sakari Ailus <sakari.ailus@iki.fi>
To: Robert Foss <robert.foss@linaro.org>
Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Tomasz Figa <tfiga@chromium.org>,
Dongchun Zhu <dongchun.zhu@mediatek.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Fabio Estevam <festevam@gmail.com>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
linux-media <linux-media@vger.kernel.org>
Subject: Re: [v2 2/3] media: ov8856: Add devicetree support
Date: Thu, 26 Mar 2020 16:47:25 +0200 [thread overview]
Message-ID: <20200326144725.GA2394@valkosipuli.retiisi.org.uk> (raw)
In-Reply-To: <CAG3jFytpx8_+DKhUVZnUFeMYK82Z1hFWcEnbyD0=4a8p3ojteg@mail.gmail.com>
Hi Robert,
On Thu, Mar 26, 2020 at 12:56:37PM +0100, Robert Foss wrote:
...
> > > +static int __ov8856_power_on(struct ov8856 *ov8856)
> > > +{
> > > + struct i2c_client *client = v4l2_get_subdevdata(&ov8856->sd);
> > > + int ret;
> > > +
> > > + ret = clk_prepare_enable(ov8856->xvclk);
> > > + if (ret < 0) {
> > > + dev_err(&client->dev, "failed to enable xvclk\n");
> > > + return ret;
> > > + }
> > > +
> > > + gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_HIGH);
> > > +
> > > + ret = regulator_bulk_enable(ARRAY_SIZE(ov8856_supply_names),
> > > + ov8856->supplies);
> > > + if (ret < 0) {
> > > + dev_err(&client->dev, "failed to enable regulators\n");
> > > + goto disable_clk;
> > > + }
> > > +
> > > + gpiod_set_value_cansleep(ov8856->reset_gpio, GPIOD_OUT_LOW);
> > > +
> > > + usleep_range(1500, 1800);
> >
> > I think you could omit the delay on ACPI based systems. Or just bail out
> > early in that case.
>
> I'll add a check for reset_gpio being NULL, and skip the sleep for that case.
There could also be a regulator but no GPIO.
I think if you don't have either, then certainly there's no need for a
delay.
...
> > > + ov8856->xvclk = NULL;
> > > + } else if (IS_ERR(ov8856->xvclk)) {
> > > + dev_err(&client->dev, "could not get xvclk clock (%ld)\n",
> > > + PTR_ERR(ov8856->xvclk));
> > > + return PTR_ERR(ov8856->xvclk);
> > > + }
> > > +
> > > + ret = clk_set_rate(ov8856->xvclk, OV8856_XVCLK_24);
> >
> > This should either come from platform data, or perhaps it'd be even better
> > to get the clock rate and use assigned-clock-rates. I guess that's
> > preferred nowadays.
>
> I'm a bit unsure about what this would look like.
>
> Are you thinking something like the way ext_clk is used in smiapp_core.c?
> I went ahead and implemented support for retrieving and storing
> 'clock-rates' during the ov8856_check_hwcfg() call, and then setting
> the rate to the configured rate during probing.
With assigned-clock-rates, you can simply use clk_get_rate().
As you get the actual rate, it could be somewhat off of the intended one.
--
Kind regards,
Sakari Ailus
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next prev parent reply other threads:[~2020-03-26 14:47 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 11:03 [v2 0/3] media: ov8856: Add devicetree support Robert Foss
2020-03-13 11:03 ` [v2 1/3] media: dt-bindings: ov8856: Document YAML bindings Robert Foss
2020-03-13 12:19 ` Sakari Ailus
2020-03-13 22:00 ` Rob Herring
2020-03-13 11:03 ` [v2 2/3] media: ov8856: Add devicetree support Robert Foss
2020-03-13 12:17 ` Sakari Ailus
2020-03-26 11:56 ` Robert Foss
2020-03-26 14:47 ` Sakari Ailus [this message]
2020-03-27 10:32 ` Robert Foss
2020-03-27 13:37 ` Sakari Ailus
2020-03-13 12:28 ` Andy Shevchenko
2020-03-13 13:15 ` Fabio Estevam
2020-03-31 13:37 ` Robert Foss
2020-03-31 13:42 ` Fabio Estevam
2020-03-31 13:53 ` Andy Shevchenko
2020-03-13 11:03 ` [v2 3/3] media: ov8856: Implement sensor module revision identification Robert Foss
2020-03-13 12:43 ` Sakari Ailus
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