Re: [PATCH v1 1/5] pwm: mediatek: add a property "mediatek,num-pwms"

Matthias Brugger
2019-01-18T08:43:53Z

On 18/01/2019 04:24, Ryder Lee wrote:
> This adds a property "mediatek,num-pwms" to avoid having an endless
> list of compatibles with no differences for the same driver.
>
> Thus, the driver should have backwards compatibility to older DTs.
>
> Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
> ---
> Changes since v1: add some checks for backwards compatibility.
> ---
> drivers/pwm/pwm-mediatek.c | 27 ++++++++++++++++++---------
> 1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
> index eb6674c..81b7e5e 100644
> --- a/drivers/pwm/pwm-mediatek.c
> +++ b/drivers/pwm/pwm-mediatek.c
> @@ -55,7 +55,7 @@ enum {
> };
>
> struct mtk_pwm_platform_data {
> - unsigned int num_pwms;
> + unsigned int num_pwms; /* it should not be used in the future SoCs */
> bool pwm45_fixup;
> bool has_clks;
> };
> @@ -226,27 +226,36 @@ static void mtk_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
>
> static int mtk_pwm_probe(struct platform_device *pdev)
> {
> - const struct mtk_pwm_platform_data *data;
> + struct device_node *np = pdev->dev.of_node;
> struct mtk_pwm_chip *pc;
> struct resource *res;
> - unsigned int i;
> + unsigned int i, num_pwms;
> int ret;
>
> pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
> if (!pc)
> return -ENOMEM;
>
> - data = of_device_get_match_data(&pdev->dev);
> - if (data == NULL)
> - return -EINVAL;
> - pc->soc = data;
> + pc->soc = of_device_get_match_data(&pdev->dev);
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> pc->regs = devm_ioremap_resource(&pdev->dev, res);
> if (IS_ERR(pc->regs))
> return PTR_ERR(pc->regs);
>
> - for (i = 0; i < data->num_pwms + 2 && pc->soc->has_clks; i++) {
> + /* Check if we have set 'num-pwms' in DTs. */
> + ret = of_property_read_u32(np, "mediatek,num-pwms", &num_pwms);
> + if (ret < 0) {
> + /* If no, fallback to use SoC data for backwards compatibility. */
> + if (pc->soc->num_pwms) {
> + num_pwms = pc->soc->num_pwms;

Maybe that's bike shedding, but I think it would be better to carve out the
num_pwms from the mtk_pwm_platform_data and check against the compatible here.
With a expressive comment it will help other driver developers to not start
adding num_pwms in the platform data in their first attempt.

Regards,
Matthias

> + } else {
> + dev_err(&pdev->dev, "failed to get pwm number: %d\n", ret);
> + return ret;
> + }
> + }
> +
> + for (i = 0; i < num_pwms + 2 && pc->soc->has_clks; i++) {
> pc->clks[i] = devm_clk_get(&pdev->dev, mtk_pwm_clk_name[i]);
> if (IS_ERR(pc->clks[i])) {
> dev_err(&pdev->dev, "clock: %s fail: %ld\n",
> @@ -260,7 +269,7 @@ static int mtk_pwm_probe(struct platform_device *pdev)
> pc->chip.dev = &pdev->dev;
> pc->chip.ops = &mtk_pwm_ops;
> pc->chip.base = -1;
> - pc->chip.npwm = data->num_pwms;
> + pc->chip.npwm = num_pwms;
>
> ret = pwmchip_add(&pc->chip);
> if (ret < 0) {
>