[PATCH v2 1/2] platform/chrome: cros_ec_proto: ignore unnecessary wakeups on old ECs

[PATCH v2 1/2] platform/chrome: cros_ec_proto: ignore unnecessary wakeups on old ECs

[Brian Norris]

ECs that don't implement EC_CMD_HOST_EVENT_GET_WAKE_MASK should still
have some reasonable default mask -- otherwise, they'll treat a variety
of EC signals as spurious wakeups. Battery and AC events can be
especially common, for devices that have been sitting at full charge
plugged into AC for a long time, as they may cycle their charging off
and on, or their battery may start reporting failures as it ages.

Treating these as wakeups does not serve a useful purpose, and is
instead often counterproductive. And indeed, later ECs (that implement
the mask) don't include these events in their wake-mask.

Note that this patch doesn't do anything without the subsequent patch
("platform/chrome: cros_ec_proto: check for missing
EC_CMD_HOST_EVENT_GET_WAKE_MASK"), because
cros_ec_get_host_event_wake_mask() currently does not return an error if
EC_CMD_HOST_EVENT_GET_WAKE_MASK is not implemented.

Some additional notes:
While the EC typically knows not to wake the CPU for these unimportant
events once the CPU reaches a sleep state, it doesn't really have a way
to know that the CPU is "almost" asleep, unless it has support for
EC_CMD_HOST_SLEEP_EVENT. Alas, these older ECs do not support that
command either, so this solution is not 100% complete.

Signed-off-by: Brian Norris <briannorris@chromium.org>
---
v2:
 * more notes in commit message
---
 drivers/platform/chrome/cros_ec_proto.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index 3e745e0fe092..e93024b55ce8 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -469,14 +469,26 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
 						    &ver_mask);
 	ec_dev->host_sleep_v1 = (ret >= 0 && (ver_mask & EC_VER_MASK(1)));
 
-	/*
-	 * Get host event wake mask, assume all events are wake events
-	 * if unavailable.
-	 */
+	/* Get host event wake mask. */
 	ret = cros_ec_get_host_event_wake_mask(ec_dev, proto_msg,
 					       &ec_dev->host_event_wake_mask);
-	if (ret < 0)
-		ec_dev->host_event_wake_mask = U32_MAX;
+	if (ret < 0) {
+		/*
+		 * If the EC doesn't support EC_CMD_HOST_EVENT_GET_WAKE_MASK,
+		 * use a reasonable default. Note that we ignore various
+		 * battery, AC status, and power-state events, because (a)
+		 * those can be quite common (e.g., when sitting at full
+		 * charge, on AC) and (b) these are not actionable wake events;
+		 * if anything, we'd like to continue suspending (to save
+		 * power), not wake up.
+		 */
+		ec_dev->host_event_wake_mask = U32_MAX &
+			~(BIT(EC_HOST_EVENT_AC_DISCONNECTED) |
+			  BIT(EC_HOST_EVENT_BATTERY_LOW) |
+			  BIT(EC_HOST_EVENT_BATTERY_CRITICAL) |
+			  BIT(EC_HOST_EVENT_PD_MCU) |
+			  BIT(EC_HOST_EVENT_BATTERY_STATUS));
+	}
 
 	ret = 0;
 
-- 
2.28.0.rc0.142.g3c755180ce-goog

[PATCH v2 2/2] platform/chrome: cros_ec_proto: check for missing EC_CMD_HOST_EVENT_GET_WAKE_MASK

[Brian Norris]

As with cros_ec_cmd_xfer_status(), etc., it's not enough to simply check
for the return status of send_command() -- that only covers transport or
other similarly-fatal errors. One must also check the ->result field, to
see whether the command really succeeded. If not, we can't use the data
it returns.

The caller of cros_ec_get_host_event_wake_mask() ignores this, and so
for example, on EC's where the command is not implemented, we're using
junk (or in practice, all zeros) for our wake-mask. We should be using a
non-zero default (currently, it's supposed to be all-1's).

Fix this by checking the ->result field and returning -EPROTO for
errors.

I might label this as fixing commit 29d99b966d60 ("cros_ec: Don't signal
wake event for non-wake host events"), except that this fix alone
actually may make things worse, as it now allows for a lot more spurious
wakeups. The patch "platform/chrome: cros_ec_proto: ignore battery/AC
wakeups on old ECs" helps to mitigate this.

Signed-off-by: Brian Norris <briannorris@chromium.org>
---
v2:
 * EOPNOTSUPP, not ENOTSUPP
---
 drivers/platform/chrome/cros_ec_proto.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index e93024b55ce8..31ca0af62388 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -208,6 +208,12 @@ static int cros_ec_get_host_event_wake_mask(struct cros_ec_device *ec_dev,
 	msg->insize = sizeof(*r);
 
 	ret = send_command(ec_dev, msg);
+	if (ret >= 0) {
+		if (msg->result == EC_RES_INVALID_COMMAND)
+			return -EOPNOTSUPP;
+		if (msg->result != EC_RES_SUCCESS)
+			return -EPROTO;
+	}
 	if (ret > 0) {
 		r = (struct ec_response_host_event_mask *)msg->data;
 		*mask = r->mask;
@@ -488,6 +494,13 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
 			  BIT(EC_HOST_EVENT_BATTERY_CRITICAL) |
 			  BIT(EC_HOST_EVENT_PD_MCU) |
 			  BIT(EC_HOST_EVENT_BATTERY_STATUS));
+		/*
+		 * Old ECs may not support this command. Complain about all
+		 * other errors.
+		 */
+		if (ret != -EOPNOTSUPP)
+			dev_err(ec_dev->dev,
+				"failed to retrieve wake mask: %d\n", ret);
 	}
 
 	ret = 0;
-- 
2.28.0.rc0.142.g3c755180ce-goog

Re: [PATCH v2 2/2] platform/chrome: cros_ec_proto: check for missing EC_CMD_HOST_EVENT_GET_WAKE_MASK

[Enric Balletbo i Serra]

Hi Brian,

On 24/7/20 21:08, Brian Norris wrote:
> As with cros_ec_cmd_xfer_status(), etc., it's not enough to simply check
> for the return status of send_command() -- that only covers transport or
> other similarly-fatal errors. One must also check the ->result field, to
> see whether the command really succeeded. If not, we can't use the data
> it returns.
> 
> The caller of cros_ec_get_host_event_wake_mask() ignores this, and so
> for example, on EC's where the command is not implemented, we're using
> junk (or in practice, all zeros) for our wake-mask. We should be using a
> non-zero default (currently, it's supposed to be all-1's).
> 
> Fix this by checking the ->result field and returning -EPROTO for
> errors.
> 
> I might label this as fixing commit 29d99b966d60 ("cros_ec: Don't signal
> wake event for non-wake host events"), except that this fix alone
> actually may make things worse, as it now allows for a lot more spurious
> wakeups. The patch "platform/chrome: cros_ec_proto: ignore battery/AC
> wakeups on old ECs" helps to mitigate this.
> 
> Signed-off-by: Brian Norris <briannorris@chromium.org>

Sorry for late notice. The patch has been applied for 5.9.

> ---
> v2:
>  * EOPNOTSUPP, not ENOTSUPP
> ---
>  drivers/platform/chrome/cros_ec_proto.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index e93024b55ce8..31ca0af62388 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -208,6 +208,12 @@ static int cros_ec_get_host_event_wake_mask(struct cros_ec_device *ec_dev,
>  	msg->insize = sizeof(*r);
>  
>  	ret = send_command(ec_dev, msg);
> +	if (ret >= 0) {
> +		if (msg->result == EC_RES_INVALID_COMMAND)
> +			return -EOPNOTSUPP;
> +		if (msg->result != EC_RES_SUCCESS)
> +			return -EPROTO;
> +	}
>  	if (ret > 0) {
>  		r = (struct ec_response_host_event_mask *)msg->data;
>  		*mask = r->mask;
> @@ -488,6 +494,13 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
>  			  BIT(EC_HOST_EVENT_BATTERY_CRITICAL) |
>  			  BIT(EC_HOST_EVENT_PD_MCU) |
>  			  BIT(EC_HOST_EVENT_BATTERY_STATUS));
> +		/*
> +		 * Old ECs may not support this command. Complain about all
> +		 * other errors.
> +		 */
> +		if (ret != -EOPNOTSUPP)
> +			dev_err(ec_dev->dev,
> +				"failed to retrieve wake mask: %d\n", ret);
>  	}
>  
>  	ret = 0;
> 

Re: [PATCH v2 1/2] platform/chrome: cros_ec_proto: ignore unnecessary wakeups on old ECs

[Enric Balletbo i Serra]

Hi Brian,

On 24/7/20 21:08, Brian Norris wrote:
> ECs that don't implement EC_CMD_HOST_EVENT_GET_WAKE_MASK should still
> have some reasonable default mask -- otherwise, they'll treat a variety
> of EC signals as spurious wakeups. Battery and AC events can be
> especially common, for devices that have been sitting at full charge
> plugged into AC for a long time, as they may cycle their charging off
> and on, or their battery may start reporting failures as it ages.
> 
> Treating these as wakeups does not serve a useful purpose, and is
> instead often counterproductive. And indeed, later ECs (that implement
> the mask) don't include these events in their wake-mask.
> 
> Note that this patch doesn't do anything without the subsequent patch
> ("platform/chrome: cros_ec_proto: check for missing
> EC_CMD_HOST_EVENT_GET_WAKE_MASK"), because
> cros_ec_get_host_event_wake_mask() currently does not return an error if
> EC_CMD_HOST_EVENT_GET_WAKE_MASK is not implemented.
> 
> Some additional notes:
> While the EC typically knows not to wake the CPU for these unimportant
> events once the CPU reaches a sleep state, it doesn't really have a way
> to know that the CPU is "almost" asleep, unless it has support for
> EC_CMD_HOST_SLEEP_EVENT. Alas, these older ECs do not support that
> command either, so this solution is not 100% complete.
> 
> Signed-off-by: Brian Norris <briannorris@chromium.org>

Sorry for late notice. The patch has been applied for 5.9.

> ---
> v2:
>  * more notes in commit message
> ---
>  drivers/platform/chrome/cros_ec_proto.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index 3e745e0fe092..e93024b55ce8 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -469,14 +469,26 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev)
>  						    &ver_mask);
>  	ec_dev->host_sleep_v1 = (ret >= 0 && (ver_mask & EC_VER_MASK(1)));
>  
> -	/*
> -	 * Get host event wake mask, assume all events are wake events
> -	 * if unavailable.
> -	 */
> +	/* Get host event wake mask. */
>  	ret = cros_ec_get_host_event_wake_mask(ec_dev, proto_msg,
>  					       &ec_dev->host_event_wake_mask);
> -	if (ret < 0)
> -		ec_dev->host_event_wake_mask = U32_MAX;
> +	if (ret < 0) {
> +		/*
> +		 * If the EC doesn't support EC_CMD_HOST_EVENT_GET_WAKE_MASK,
> +		 * use a reasonable default. Note that we ignore various
> +		 * battery, AC status, and power-state events, because (a)
> +		 * those can be quite common (e.g., when sitting at full
> +		 * charge, on AC) and (b) these are not actionable wake events;
> +		 * if anything, we'd like to continue suspending (to save
> +		 * power), not wake up.
> +		 */
> +		ec_dev->host_event_wake_mask = U32_MAX &
> +			~(BIT(EC_HOST_EVENT_AC_DISCONNECTED) |
> +			  BIT(EC_HOST_EVENT_BATTERY_LOW) |
> +			  BIT(EC_HOST_EVENT_BATTERY_CRITICAL) |
> +			  BIT(EC_HOST_EVENT_PD_MCU) |
> +			  BIT(EC_HOST_EVENT_BATTERY_STATUS));
> +	}
>  
>  	ret = 0;
>  
>