Re: [PATCH] mfd: cros_ec: Add support for MKBP more event flags

[Brian Norris <briannorris@chromium.org>]

Hi Enrico,

On Thu, Nov 29, 2018 at 11:55:48AM -0800, egranata@google.com wrote:
> From: Enrico Granata <egranata@chromium.org>
> 
> The ChromeOS EC has support for signaling to the host that
> a single IRQ can serve multiple MKBP events.
> 
> Doing this serves an optimization purpose, as it minimizes the
> number of round-trips into the interrupt handling machinery, and
> it proves beneficial to sensor timestamping as it keeps the desired
> synchronization of event times between the two processors.
> 
> This patch adds kernel support for this EC feature, allowing the
> ec_irq to loop until all events have been served.

Might be worth being more explicit in this commit message to say that
you're adding support for EC_CMD_GET_NEXT_EVENT version 2?

> Signed-off-by: Enrico Granata <egranata@chromium.org>

Mostly looks fine; thanks for sending. I have a few small notes (and
some of that is not necessarily something resolve in this patch), but
with at least the cros_ec.h comment fixup, feel free to add my:

Reviewed-by: Brian Norris <briannorris@chromium.org>

> ---
>  drivers/mfd/cros_ec.c                   | 20 +++++++++++++--
>  drivers/platform/chrome/cros_ec_proto.c | 33 +++++++++++--------------
>  include/linux/mfd/cros_ec.h             |  3 ++-
>  include/linux/mfd/cros_ec_commands.h    | 15 +++++++++++
>  4 files changed, 50 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/mfd/cros_ec.c b/drivers/mfd/cros_ec.c
> index fe6f83766144f..17903a378aa1a 100644
> --- a/drivers/mfd/cros_ec.c
> +++ b/drivers/mfd/cros_ec.c
> @@ -51,13 +51,16 @@ static const struct mfd_cell ec_pd_cell = {
>  	.pdata_size = sizeof(pd_p),
>  };
>  
> -static irqreturn_t ec_irq_thread(int irq, void *data)
> +static bool ec_handle_event(struct cros_ec_device *ec_dev)
>  {
> -	struct cros_ec_device *ec_dev = data;
>  	bool wake_event = true;
>  	int ret;
> +	bool ec_has_more_events = false;
>  
>  	ret = cros_ec_get_next_event(ec_dev, &wake_event);
> +	if (ret > 0)
> +		ec_has_more_events =
> +			ec_dev->event_data.event_type & EC_MKBP_HAS_MORE_EVENTS;
>  
>  	/*
>  	 * Signal only if wake host events or any interrupt if
> @@ -70,6 +73,19 @@ static irqreturn_t ec_irq_thread(int irq, void *data)
>  	if (ret > 0)
>  		blocking_notifier_call_chain(&ec_dev->event_notifier,
>  					     0, ec_dev);
> +
> +	return ec_has_more_events;
> +}
> +
> +static irqreturn_t ec_irq_thread(int irq, void *data)
> +{
> +	struct cros_ec_device *ec_dev = data;
> +	bool ec_has_more_events;
> +
> +	do {
> +		ec_has_more_events = ec_handle_event(ec_dev);
> +	} while (ec_has_more_events);
> +
>  	return IRQ_HANDLED;
>  }
>  
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index b6fd4838f60f3..bb126d95b2fd4 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -420,10 +420,14 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
>  	ret = cros_ec_get_host_command_version_mask(ec_dev,
>  						    EC_CMD_GET_NEXT_EVENT,
>  						    &ver_mask);

It's not exactly new here (although you're using 'ver_mask' in new
ways), but cros_ec_get_host_command_version_mask() doesn't look 100%
right. It doesn't look at msg->result, and instead just assumes that if
we got some data back (send_command() > 0), then it must have been a
success. I don't think that's really guaranteed in general, although it
might be for the specific case of EC_CMD_GET_CMD_VERSIONS.

IOW, to be definitely sure we're not looking at a garbage result in
'ver_mask', we should probably fixup
cros_ec_get_host_command_version_mask().

> -	if (ret < 0 || ver_mask == 0)
> +	if (ret < 0 || ver_mask == 0) {
>  		ec_dev->mkbp_event_supported = 0;
> -	else
> -		ec_dev->mkbp_event_supported = 1;
> +		dev_info(ec_dev->dev, "MKBP not supported\n");
> +	} else {
> +		ec_dev->mkbp_event_supported = fls(ver_mask);
> +		dev_info(ec_dev->dev, "MKBP support version %u\n",
> +			ec_dev->mkbp_event_supported - 1);
> +	}
>  
>  	/*
>  	 * Get host event wake mask, assume all events are wake events
> @@ -530,28 +534,19 @@ static int get_next_event(struct cros_ec_device *ec_dev)
>  {
>  	u8 buffer[sizeof(struct cros_ec_command) + sizeof(ec_dev->event_data)];
>  	struct cros_ec_command *msg = (struct cros_ec_command *)&buffer;
> -	static int cmd_version = 1;
> -	int ret;
> +	const int cmd_version = ec_dev->mkbp_event_supported - 1;
>  
>  	if (ec_dev->suspended) {
>  		dev_dbg(ec_dev->dev, "Device suspended.\n");
>  		return -EHOSTDOWN;
>  	}
>  
> -	if (cmd_version == 1) {
> -		ret = get_next_event_xfer(ec_dev, msg, cmd_version,
> -				sizeof(struct ec_response_get_next_event_v1));
> -		if (ret < 0 || msg->result != EC_RES_INVALID_VERSION)
> -			return ret;
> -
> -		/* Fallback to version 0 for future send attempts */
> -		cmd_version = 0;
> -	}
> -
> -	ret = get_next_event_xfer(ec_dev, msg, cmd_version,
> +	if (cmd_version == 0)
> +		return get_next_event_xfer(ec_dev, msg, 0,
>  				  sizeof(struct ec_response_get_next_event));
>  
> -	return ret;
> +	return get_next_event_xfer(ec_dev, msg, cmd_version,
> +				sizeof(struct ec_response_get_next_event_v1));
>  }
>  
>  static int get_keyboard_state_event(struct cros_ec_device *ec_dev)
> @@ -607,11 +602,13 @@ EXPORT_SYMBOL(cros_ec_get_next_event);
>  
>  u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev)
>  {
> +	u32 event_type =
> +		ec_dev->event_data.event_type & EC_MKBP_EVENT_TYPE_MASK;
>  	u32 host_event;
>  
>  	BUG_ON(!ec_dev->mkbp_event_supported);
>  
> -	if (ec_dev->event_data.event_type != EC_MKBP_EVENT_HOST_EVENT)
> +	if (event_type != EC_MKBP_EVENT_HOST_EVENT)
>  		return 0;
>  
>  	if (ec_dev->event_size != sizeof(host_event)) {
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index e44e3ec8a9c7d..eb771ceeaeed1 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -152,7 +152,8 @@ struct cros_ec_device {
>  	int (*pkt_xfer)(struct cros_ec_device *ec,
>  			struct cros_ec_command *msg);
>  	struct mutex lock;
> -	bool mkbp_event_supported;
> +	/* 0 == not supported, otherwise it supports version x - 1 */

This comment belongs in the kerneldoc, which is above the struct
definition. You're invalidating the existing comment:

 * @mkbp_event_supported: True if this EC supports the MKBP event protocol.

Brian


> +	u8 mkbp_event_supported;
>  	struct blocking_notifier_head event_notifier;
>  
>  	struct ec_response_get_next_event_v1 event_data;

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