Hi Andy,
On 24/8/2020 4:17 pm, Andy Shevchenko wrote:
> On Mon, Aug 24, 2020 at 11:36:37AM +0800, Rahul Tanwar wrote:
>> Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
>> This PWM controller does not have any other consumer, it is a
>> dedicated PWM controller for fan attached to the system. Add
>> driver for this PWM fan controller.
> ...
>
>> + pc->regmap = devm_regmap_init_mmio(dev, io_base, &lgm_pwm_regmap_config);
>> + if (IS_ERR(pc->regmap)) {
>> + ret = PTR_ERR(pc->regmap);
>> + if (ret != -EPROBE_DEFER)
>> + dev_err_probe(dev, ret, "failed to init register map\n");
>> + return ret;
>> + }
>> +
>> + pc->clk = devm_clk_get(dev, NULL);
>> + if (IS_ERR(pc->clk)) {
>> + ret = PTR_ERR(pc->clk);
>> + if (ret != -EPROBE_DEFER)
>> + dev_err_probe(dev, ret, "failed to get clock\n");
>> + return ret;
>> + }
>> +
>> + pc->rst = devm_reset_control_get_exclusive(dev, NULL);
>> + if (IS_ERR(pc->rst)) {
>> + ret = PTR_ERR(pc->rst);
>> + if (ret != -EPROBE_DEFER)
>> + dev_err_probe(dev, ret, "failed to get reset control\n");
>> + return ret;
>> + }
>> +
>> + ret = reset_control_deassert(pc->rst);
>> + if (ret) {
>> + if (ret != -EPROBE_DEFER)
>> + dev_err_probe(dev, ret, "cannot deassert reset control\n");
>> + return ret;
>> + }
> Please, spend a bit of time to understand the changes you are doing. There are
> already few examples how to use dev_err_probe() properly.
I guess your point is that the check of (ret !- -EPROBE_DEFER) is not needed
when using dev_err_probe() as it encapsulates it. Sorry, i missed it. Will
fix it. I am not able to find any other missing point after referring to
two driver examples which uses dev_err_probe() ?
>> + ret = clk_prepare_enable(pc->clk);
>> + if (ret) {
>> + dev_err(dev, "failed to enable clock\n");
>> + return ret;
>> + }
>> +
>> + ret = devm_add_action_or_reset(dev, lgm_pwm_action, pc);
>> + if (ret)
>> + return ret;
> You have also ordering issues here.
>
> So, what I can see about implementation is that
>
>
> static void ..._clk_disable(void *data)
> {
> clk_disable_unprepare(data);
> }
>
> static int ..._clk_enable(...)
> {
> int ret;
>
> ret = clk_preare_enable(...);
> if (ret)
> return ret;
> return devm_add_action_or_reset(..., ..._clk_disable);
> }
>
>
> Similar for reset control.
>
> Then in the ->probe() something like this:
>
> ret = devm_reset_control_get...;
> if (ret)
> return ret;
>
> ret = ..._reset_deassert(...);
> if (ret)
> return ret;
>
> followed by similar section for the clock.
>
Regarding ordering: In early rounds of review, feedback about ordering was that
it is recommended to be reverse of the sequence in probe i.e.
if in probe:
1. reset_control_deassert()
2. clk_prepare_enable()
then in remove:
1. clk_disable_uprepare()
2. reset_control_assert()
That's the reason i added a generic action() which reverses order.
I understand your suggested way as explained above but not sure if that would
ensure reverse ordering during unwind.
Thanks.
Regards,
Rahul
