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

Ryder Lee
2019-01-18T01:45:20Z

On Mon, 2019-01-14 at 12:16 +0100, Matthias Brugger wrote:
>
> 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?

Okay, I will do that.

Ryder
>
> >
> > 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 },
> > { },
> >