linux-kernel - Re: [v1 2/3] media: ov8856: Add devicetree support

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Message-ID: <CAOMZO5D7N6FfPMiycGun-eui-G-tbp15stwRWBWs4L98JHFfGA@mail.gmail.com>
Date:   Tue, 10 Mar 2020 11:03:21 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Robert Foss <robert.foss@...aro.org>
Cc:     ben.kao@...el.com, Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan.Cameron@...wei.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-media <linux-media@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-mediatek@...ts.infradead.org,
        Dongchun Zhu <dongchun.zhu@...iatek.com>,
        Tomasz Figa <tfiga@...omium.org>
Subject: Re: [v1 2/3] media: ov8856: Add devicetree support

On Tue, Mar 10, 2020 at 10:47 AM Robert Foss <robert.foss@...aro.org> 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->n_shutdn_gpio, GPIOD_OUT_LOW);
> +
> +       ret = regulator_bulk_enable(OV8856_NUM_SUPPLIES, ov8856->supplies);
> +       if (ret < 0) {
> +               dev_err(&client->dev, "failed to enable regulators\n");
> +               goto disable_clk;
> +       }
> +
> +       gpiod_set_value_cansleep(ov8856->n_shutdn_gpio, GPIOD_OUT_HIGH);

To power it up you probably only need:

gpiod_set_value_cansleep(ov8856->n_shutdn_gpio, 0);

And use reset-gpios as active low in your device tree. Assuming the
reset-gpios is active low like other OmniVision sensors.

> +
> +       usleep_range(1500, 1800);
> +
> +       return 0;
> +
> +disable_clk:
> +       clk_disable_unprepare(ov8856->xvclk);
> +
> +       return ret;
> +}
> +
> +static void __ov8856_power_off(struct ov8856 *ov8856)
> +{
> +       gpiod_set_value_cansleep(ov8856->n_shutdn_gpio, GPIOD_OUT_LOW);
> +       regulator_bulk_disable(OV8856_NUM_SUPPLIES, ov8856->supplies);
> +       clk_disable_unprepare(ov8856->xvclk);
> +}
> +
> +

Unneede extra blank line.

>         v4l2_i2c_subdev_init(&ov8856->sd, client, &ov8856_subdev_ops);
> +       ov8856->xvclk = devm_clk_get(&client->dev, "xvclk");
> +       if (IS_ERR(ov8856->xvclk)) {
> +               dev_err(&client->dev, "failed to get xvclk\n");
> +               return -EINVAL;

You should better return the real error insteald
PTR_ERR(ov8856->xvclk). This way defer probe could work.

> +       }
> +
> +       ret = clk_set_rate(ov8856->xvclk, OV8856_XVCLK_24);
> +       if (ret < 0) {
> +               dev_err(&client->dev, "failed to set xvclk rate (24MHz)\n");
> +               return ret;
> +       }
> +
> +       ov8856->n_shutdn_gpio = devm_gpiod_get(&client->dev, "reset",
> +                                              GPIOD_OUT_LOW);
> +       if (IS_ERR(ov8856->n_shutdn_gpio)) {
> +               dev_err(&client->dev, "failed to get reset-gpios\n");
> +               return -EINVAL;

Please return the real error.