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

Matthias Brugger
2019-01-14T11:16:49Z

On 14/01/2019 09:21, Ryder Lee wrote:
> This adds a property "mediatek,num-pwms" to avoid having an endless
> list of compatibles with no other differences for the same driver.
>
> Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
> ---
> drivers/pwm/pwm-mediatek.c | 25 +++++++++++--------------
> 1 file changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
> index eb6674c..37daa84 100644
> --- a/drivers/pwm/pwm-mediatek.c
> +++ b/drivers/pwm/pwm-mediatek.c
> @@ -55,7 +55,6 @@ enum {
> };
>
> struct mtk_pwm_platform_data {
> - unsigned int num_pwms;
> bool pwm45_fixup;
> bool has_clks;
> };
> @@ -226,10 +225,11 @@ static void mtk_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
>
> static int mtk_pwm_probe(struct platform_device *pdev)
> {
> + struct device_node *np = pdev->dev.of_node;
> const struct mtk_pwm_platform_data *data;
> 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);
> @@ -246,7 +246,13 @@ static int mtk_pwm_probe(struct platform_device *pdev)
> if (IS_ERR(pc->regs))
> return PTR_ERR(pc->regs);
>
> - for (i = 0; i < data->num_pwms + 2 && pc->soc->has_clks; i++) {
> + ret = of_property_read_u32(np, "mediatek,num-pwms", &num_pwms);
> + if (ret < 0) {
> + 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 +266,7 @@ 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) {
> @@ -279,32 +285,23 @@ static int mtk_pwm_remove(struct platform_device *pdev)
> }
>
> static const struct mtk_pwm_platform_data mt2712_pwm_data = {
> - .num_pwms = 8,
> - .pwm45_fixup = false,
> - .has_clks = true,
> -};
> -
> -static const struct mtk_pwm_platform_data mt7622_pwm_data = {
> - .num_pwms = 6,
> .pwm45_fixup = false,
> .has_clks = true,
> };

From my point of view that's not perfect. We should make sure that a newer
kernel does not break with an older device tree and vice versa.
Just imagine I use some board where u-boot passes the device tree to the kernel,
I update the kernel and PWM is broken.

So also it is crappy we will need to have the num_pwms variable for the older
boards.
Maybe put a switch in the probe function which checks the compatible with a
comment message saying that this is for legacy device tree, so that no new
contributer just copys the wrong code.

What do you think?
Regards,
Matthias

>
> static const struct mtk_pwm_platform_data mt7623_pwm_data = {
> - .num_pwms = 5,
> .pwm45_fixup = true,
> .has_clks = true,
> };
>
> static const struct mtk_pwm_platform_data mt7628_pwm_data = {
> - .num_pwms = 4,
> .pwm45_fixup = true,
> .has_clks = false,
> };
>
> static const struct of_device_id mtk_pwm_of_match[] = {
> { .compatible = "mediatek,mt2712-pwm", .data = &mt2712_pwm_data },
> - { .compatible = "mediatek,mt7622-pwm", .data = &mt7622_pwm_data },
> + { .compatible = "mediatek,mt7622-pwm", .data = &mt2712_pwm_data },
> { .compatible = "mediatek,mt7623-pwm", .data = &mt7623_pwm_data },
> { .compatible = "mediatek,mt7628-pwm", .data = &mt7628_pwm_data },
> { },
>