Messages in this thread | | | Date | Thu, 26 Mar 2020 16:47:25 +0200 | From | Sakari Ailus <> | Subject | Re: [v2 2/3] media: ov8856: Add devicetree support |
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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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