Re: [PATCH v6 1/4] Runtime Interpreted Power Sequences

[Stephen Warren]

On 09/12/2012 03:57 AM, Alexandre Courbot wrote:
> Some device drivers (panel backlights especially) need to follow precise
> sequences for powering on and off, involving gpios, regulators, PWMs
> with a precise powering order and delays to respect between each steps.
> These sequences are board-specific, and do not belong to a particular
> driver - therefore they have been performed by board-specific hook
> functions to far.
> 
> With the advent of the device tree and of ARM kernels that are not
> board-tied, we cannot rely on these board-specific hooks anymore but
> need a way to implement these sequences in a portable manner. This patch
> introduces a simple interpreter that can execute such power sequences
> encoded either as platform data or within the device tree.
> 
> Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>

> diff --git a/Documentation/power/power_seq.txt b/Documentation/power/power_seq.txt

> +Sometimes, you may want to browse the list of resources allocated by a sequence,
> +for instance to ensure that a resource of a given type is present. The
> +power_seq_set_resources() function returns a list head that can be used with
> +the power_seq_for_each_resource() macro to browse all the resources of a set:
> +
> +  struct list_head *power_seq_set_resources(struct power_seq_set *seqs);

I don't think you need to include that prototype here?

> +  power_seq_for_each_resource(pos, seqs)
> +
> +Here "pos" will be a pointer to a struct power_seq_resource. This structure
> +contains the type of the resource, the information used for identifying it, and
> +the resolved resource itself.

> diff --git a/drivers/power/power_seq/Makefile b/drivers/power/power_seq/Makefile
> new file mode 100644
> index 0000000..f77a359
> --- /dev/null
> +++ b/drivers/power/power_seq/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_POWER_SEQ)		+= power_seq.o

Don't you need to compile all the power_seq_*.c too?

Oh, I see the following in power_seq.c:

> +#include "power_seq_delay.c"
> +#include "power_seq_regulator.c"
> +#include "power_seq_pwm.c"
> +#include "power_seq_gpio.c"

It's probably better just to compile them separately and link them.

> diff --git a/drivers/power/power_seq/power_seq.c b/drivers/power/power_seq/power_seq.c

> +struct power_seq_step {
> +	/* Copy of the platform data */
> +	struct platform_power_seq_step pdata;

I'd reword the comment to "Copy of the step", and name the field "step".

> +static const struct power_seq_res_ops power_seq_types[POWER_SEQ_NUM_TYPES] = {
> +	[POWER_SEQ_DELAY] = POWER_SEQ_DELAY_TYPE,
> +	[POWER_SEQ_REGULATOR] = POWER_SEQ_REGULATOR_TYPE,
> +	[POWER_SEQ_PWM] = POWER_SEQ_PWM_TYPE,
> +	[POWER_SEQ_GPIO] = POWER_SEQ_GPIO_TYPE,
> +};

Ah, I see why you're using #include now.

> +MODULE_LICENSE("GPL");

s/GPL/GPL v2/ given the license header.

> diff --git a/drivers/power/power_seq/power_seq_gpio.c b/drivers/power/power_seq/power_seq_gpio.c

> +static int power_seq_res_alloc_gpio(struct device *dev,
> +				    struct platform_power_seq_step *pstep,
> +				    struct power_seq_resource *res)
> +{
> +	int err;
> +
> +	err = devm_gpio_request_one(dev, pstep->gpio.gpio,
> +				    GPIOF_OUT_INIT_LOW, dev_name(dev));

Hmm. The INIT_LOW part of that might be somewhat presumptive. I would
suggest simply requesting the GPIO here, and using
gpio_direction_output() in power_seq_step_run_gpio(), thus deferring the
decision of what value to set the GPIO to until a real sequence is
actually run.

> diff --git a/drivers/power/power_seq/power_seq_pwm.c b/drivers/power/power_seq/power_seq_pwm.c

> diff --git a/drivers/power/power_seq/power_seq_regulator.c b/drivers/power/power_seq/power_seq_regulator.c

> diff --git a/include/linux/power_seq.h b/include/linux/power_seq.h

> +#include <net/irda/parameters.h>

That looks out of place.

> +/**
> + * struct power_seq_resource - resource used by a power sequence set
> + * @pdata:	Pointer to the platform data used to resolve this resource
> + * @regulator:	Resolved regulator if of type POWER_SEQ_REGULATOR
> + * @pwm:	Resolved PWM if of type POWER_SEQ_PWM
> + * @list:	Used to link resources together
> + */

I think that kerneldoc is stale.

> +struct power_seq_resource {
> +	enum power_seq_res_type type;
> +	/* resolved resource and identifier */
> +	union {
> +		struct {
> +			struct regulator *regulator;
> +			const char *id;
> +		} regulator;
> +		struct {
> +			struct pwm_device *pwm;
> +			const char *id;
> +		} pwm;
> +		struct {
> +			int gpio;
> +		} gpio;
> +	};
> +	struct list_head list;
> +};

Aside from those minor issues, this all looks reasonable to me, so,
Reviewed-by: Stephen Warren <swarren@xxxxxxxxxxxxx>
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