On 12.10.2018 15:15, Thierry Reding wrote:
> On Tue, Aug 28, 2018 at 04:01:25PM +0300, Claudiu Beznea wrote:
>> Add documentation for PWM push-pull mode.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.bez...@microchip.com>
>> Reviewed-by: Rob Herring <r...@kernel.org>
>> ---
>> Documentation/devicetree/bindings/pwm/pwm.txt | 2 ++
>> Documentation/pwm.txt | 16 ++++++++++++++++
>> include/dt-bindings/pwm/pwm.h | 1 +
>> 3 files changed, 19 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt
>> b/Documentation/devicetree/bindings/pwm/pwm.txt
>> index 7c8aaac43f92..6a60c0fca112 100644
>> --- a/Documentation/devicetree/bindings/pwm/pwm.txt
>> +++ b/Documentation/devicetree/bindings/pwm/pwm.txt
>> @@ -49,6 +49,8 @@ Optionally, the pwm-specifier can encode a number of flags
>> (defined in
>> - PWM_MODE_COMPLEMENTARY: PWM complementary working mode (for PWM channels
>> with two outputs); if not specified, the default for PWM channel will be
>> used
>> +- PWM_MODE_PUSH_PULL: PWM push-pull working modes (for PWM channels with
>> +two outputs); if not specified the default for PWM channel will be used
>
> What if somebody has this in the DT:
>
> PWM_MODE_COMPLEMENTARY | PWM_MODE_PUSH_PULL
>
> which one takes precedence, or do we reject it?
The first valid one will be selected.
In patch 1/1 from this series, changes added to of_pwm_xlate_with_flags()
function, there is this code:
+ for (modebit = PWMC_MODE_COMPLEMENTARY_BIT;
+ modebit < PWMC_MODE_CNT; modebit++) {
+ unsigned long mode = BIT(modebit);
+
+ if ((args->args[2] & mode) &&
+ pwm_mode_valid(pwm, mode)) {
+ pwm->args.mode = mode;
+ break;
+ }
+ }
And since the modes bits are defined as follows:
enum {
PWMC_MODE_NORMAL_BIT,
PWMC_MODE_COMPLEMENTARY_BIT,
PWMC_MODE_PUSH_PULL_BIT,
PWMC_MODE_CNT,
};
in your proposed scenario: PWM_MODE_COMPLEMENTARY | PWM_MODE_PUSH_PULL
the PWM_MODE_COMPLEMENTARY mode will be selected since it is the first
valid one.
>
> Wouldn't it be preferable to either move the modes into an extra field
> within the flags field, or perhaps even add another field?
This approach was proposed in version 2 of this series and based on the
discussions I had with Rob Herring [1] I decided to use the remaining space
from cell specific to PWM flags.
Thank you,
Claudiu Beznea
[1] https://lkml.org/lkml/2018/1/22/655
>
> I guess since Rob's already acked this, that concern may be unfounded.
>
> Thierry
>
>
>
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