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SubjectRe: [PATCH v4 3/7] pwm: sun4i: Add an optional probe for bus clock
On Fri, Nov 08, 2019 at 09:45:13AM +0100, Clément Péron wrote:
> From: Jernej Skrabec <jernej.skrabec@siol.net>
>
> H6 PWM core needs bus clock to be enabled in order to work.
>
> Add an optional probe for it and a fallback for previous
> bindings without name on module clock.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> Signed-off-by: Clément Péron <peron.clem@gmail.com>
> ---
> drivers/pwm/pwm-sun4i.c | 48 +++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 46 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 2b9a2a78591f..a10022d6c0fd 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -78,6 +78,7 @@ struct sun4i_pwm_data {
>
> struct sun4i_pwm_chip {
> struct pwm_chip chip;
> + struct clk *bus_clk;
> struct clk *clk;
> struct reset_control *rst;
> void __iomem *base;
> @@ -363,9 +364,38 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
> if (IS_ERR(pwm->base))
> return PTR_ERR(pwm->base);
>
> - pwm->clk = devm_clk_get(&pdev->dev, NULL);
> - if (IS_ERR(pwm->clk))
> + /* Get all clocks and reset line */
> + pwm->clk = devm_clk_get_optional(&pdev->dev, "mod");
> + if (IS_ERR(pwm->clk)) {
> + if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> + dev_err(&pdev->dev, "get clock failed %pe\n",
> + pwm->clk);
> return PTR_ERR(pwm->clk);
> + }
> +
> + /*
> + * Fallback for old dtbs with a single clock and no name.
> + * If a parent has a clock-name called "mod" whereas the
> + * current node is unnamed the clock reference will be
> + * incorrectly obtained and will not go into this fallback.

For me "old dtbs" suggests that today a device tree should have a "mod"
clock. Is this true also for machines other than H6? And I'd put the
comment before the acquisition of the "mod" clock. Something like:

/*
* A clock called "mod" is only required on H6 (for now) and on
* other SoCs we expect an unnamed clock. So we request "mod"
* first (and ignore the corner case that a parent provides a
* "mod" clock) and if this is not found we fall back to the
* first clock of the PWM.
*/

> + */
> + if (!pwm->clk) {
> + pwm->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(pwm->clk)) {
> + if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> + dev_err(&pdev->dev, "get clock failed %pe\n",
> + pwm->clk);
> + return PTR_ERR(pwm->clk);
> + }
> + }
> +
> + pwm->bus_clk = devm_clk_get_optional(&pdev->dev, "bus");
> + if (IS_ERR(pwm->bus_clk)) {
> + if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
> + dev_err(&pdev->dev, "get bus_clock failed %pe\n",
> + pwm->bus_clk);
> + return PTR_ERR(pwm->bus_clk);
> + }
>
> pwm->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
> if (IS_ERR(pwm->rst)) {
> @@ -382,6 +412,17 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
> return ret;
> }
>
> + /*
> + * We're keeping the bus clock on for the sake of simplicity.
> + * Actually it only needs to be on for hardware register
> + * accesses.
> + */
> + ret = clk_prepare_enable(pwm->bus_clk);
> + if (ret) {
> + dev_err(&pdev->dev, "Cannot prepare and enable bus_clk\n");
> + goto err_bus;
> + }
> +

Would it make sense to split this patch into "Prefer "mod" clock to
(unnamed) clock" and "Introduce optional bus clock"?

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |

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