[PATCH] ACPI / EC: Improve busy polling quirk.

[PATCH] ACPI / EC: Improve busy polling quirk.

[Lv Zheng]

The busy polling mode (EC_FLAGS_MSI) can be used to workaround some GPIO
driver bugs. After their initialization, the PIN configuration of the EC
GPE may be cleared and the EC GPE might be disabled out of the
GPE register's control. And the busy polling can significantly shorten the
EC driver waiting time in this situation while the wait_event_timeout() has
to wait the basic HZ interval.

In order to improve the busy polling mode, this patch:
1. Removes a useless polling guarding logic which has been covered by many
   state machine race fixes.
2. Refines the delay logic to tune it to poll faster by spinning around the
   EC_SC read instead of spinning around the nop execution lasted a
   determined interval.
3. Deletes irqs_disabled() check as ec_poll() is ensured to be invoked in
   the contexts that can sleep.
4. Adds logic to do busy polling when the EC GPE is disabled.

This patch also updates acpi_ec_is_gpe_raised() according to the following
commit:
  Commit: 09af8e8290deaff821ced01ea83594ee4c21e8df
  Subject: ACPICA: Events: Add support to return both enable/status register values for GPE and fixed event.
This is actually a no-op change as both the flags are defined to a same
value.

We've tested the patch on a test platform. The platform suffers from such
kind of the GPIO PIN issue. The GPIO driver resets all PIN configuration
and after that, EC interrupt cannot arrive because of the multiplexing.
Then the platform suffers from a long delay carried out by the
wait_event_timeout() as all further EC transactions will run in the polling
mode. We switched the EC driver to use the busy polling mechanism instead
of the wait timeout polling mechanism and the delay is still high:
[   44.283005] calling  PNP0C0B:00+ @ 1305, parent: platform
[   44.417548] call PNP0C0B:00+ returned 0 after 131323 usecs
And this patch can significantly reduce the delay:
[   44.502625] calling  PNP0C0B:00+ @ 1308, parent: platform
[   44.503760] call PNP0C0B:00+ returned 0 after 1103 usecs

Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 5e8fed4..e98c242 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -70,7 +70,6 @@ enum ec_command {
 
 #define ACPI_EC_DELAY		500	/* Wait 500ms max. during EC ops */
 #define ACPI_EC_UDELAY_GLK	1000	/* Wait 1ms max. to get global lock */
-#define ACPI_EC_MSI_UDELAY	550	/* Wait 550us for MSI EC */
 #define ACPI_EC_UDELAY_POLL	1000	/* Wait 1ms for EC transaction polling */
 #define ACPI_EC_CLEAR_MAX	100	/* Maximum number of events to query
 					 * when trying to clear the EC */
@@ -262,12 +261,20 @@ static const char *acpi_ec_cmd_string(u8 cmd)
  *                           GPE Registers
  * -------------------------------------------------------------------------- */
 
+static inline bool acpi_ec_is_gpe_enabled(struct acpi_ec *ec)
+{
+	acpi_event_status gpe_status = 0;
+
+	(void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
+	return (gpe_status & ACPI_EVENT_FLAG_ENABLE_SET) ? true : false;
+}
+
 static inline bool acpi_ec_is_gpe_raised(struct acpi_ec *ec)
 {
 	acpi_event_status gpe_status = 0;
 
 	(void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
-	return (gpe_status & ACPI_EVENT_FLAG_SET) ? true : false;
+	return (gpe_status & ACPI_EVENT_FLAG_STATUS_SET) ? true : false;
 }
 
 static inline void acpi_ec_enable_gpe(struct acpi_ec *ec, bool open)
@@ -505,9 +512,7 @@ static int ec_poll(struct acpi_ec *ec)
 		unsigned long usecs = ACPI_EC_UDELAY_POLL;
 		do {
 			/* don't sleep with disabled interrupts */
-			if (EC_FLAGS_MSI || irqs_disabled()) {
-				usecs = ACPI_EC_MSI_UDELAY;
-				udelay(usecs);
+			if (EC_FLAGS_MSI || !acpi_ec_is_gpe_enabled(ec)) {
 				if (ec_transaction_completed(ec))
 					return 0;
 			} else {
@@ -517,7 +522,9 @@ static int ec_poll(struct acpi_ec *ec)
 					return 0;
 			}
 			spin_lock_irqsave(&ec->lock, flags);
-			if (time_after(jiffies,
+			if (EC_FLAGS_MSI ||
+			    !acpi_ec_is_gpe_enabled(ec) ||
+			    time_after(jiffies,
 					ec->curr->timestamp +
 					usecs_to_jiffies(usecs)))
 				advance_transaction(ec);
@@ -537,8 +544,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	unsigned long tmp;
 	int ret = 0;
 
-	if (EC_FLAGS_MSI)
-		udelay(ACPI_EC_MSI_UDELAY);
 	/* start transaction */
 	spin_lock_irqsave(&ec->lock, tmp);
 	/* Enable GPE for command processing (IBF=0/OBF=1) */
-- 
1.7.10

RE: [PATCH] ACPI / EC: Improve busy polling quirk.

[Zheng, Lv]

Hi, Rafael

Since we've implemented register access guarding in the wait polling mode in this commit:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=9e295ac
So all udelay() quirks may be no longer necessary and we can remove it.
I'm asking an original reporter to confirm this:
https://bugzilla.kernel.org/show_bug.cgi?id=77431
After removing the udelay() quirk we can turn it to be a special usage model:
Do busy polling as a non-default behavior using a module param so that it is still useful for debugging.

This commit cannot reflect all of the above stories and may leave regressions for guarding required platforms.
Please ignore it and I'll prepare a better patchset for this.

Thanks and best regards
-Lv

> From: Zheng, Lv
> Sent: Monday, May 11, 2015 11:38 AM
> 
> The busy polling mode (EC_FLAGS_MSI) can be used to workaround some GPIO
> driver bugs. After their initialization, the PIN configuration of the EC
> GPE may be cleared and the EC GPE might be disabled out of the
> GPE register's control. And the busy polling can significantly shorten the
> EC driver waiting time in this situation while the wait_event_timeout() has
> to wait the basic HZ interval.
> 
> In order to improve the busy polling mode, this patch:
> 1. Removes a useless polling guarding logic which has been covered by many
>    state machine race fixes.
> 2. Refines the delay logic to tune it to poll faster by spinning around the
>    EC_SC read instead of spinning around the nop execution lasted a
>    determined interval.
> 3. Deletes irqs_disabled() check as ec_poll() is ensured to be invoked in
>    the contexts that can sleep.
> 4. Adds logic to do busy polling when the EC GPE is disabled.
> 
> This patch also updates acpi_ec_is_gpe_raised() according to the following
> commit:
>   Commit: 09af8e8290deaff821ced01ea83594ee4c21e8df
>   Subject: ACPICA: Events: Add support to return both enable/status register values for GPE and fixed event.
> This is actually a no-op change as both the flags are defined to a same
> value.
> 
> We've tested the patch on a test platform. The platform suffers from such
> kind of the GPIO PIN issue. The GPIO driver resets all PIN configuration
> and after that, EC interrupt cannot arrive because of the multiplexing.
> Then the platform suffers from a long delay carried out by the
> wait_event_timeout() as all further EC transactions will run in the polling
> mode. We switched the EC driver to use the busy polling mechanism instead
> of the wait timeout polling mechanism and the delay is still high:
> [   44.283005] calling  PNP0C0B:00+ @ 1305, parent: platform
> [   44.417548] call PNP0C0B:00+ returned 0 after 131323 usecs
> And this patch can significantly reduce the delay:
> [   44.502625] calling  PNP0C0B:00+ @ 1308, parent: platform
> [   44.503760] call PNP0C0B:00+ returned 0 after 1103 usecs
> 
> Tested-by: Chen Yu <yu.c.chen@intel.com>
> Signed-off-by: Lv Zheng <lv.zheng@intel.com>
> ---
>  drivers/acpi/ec.c |   21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index 5e8fed4..e98c242 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -70,7 +70,6 @@ enum ec_command {
> 
>  #define ACPI_EC_DELAY		500	/* Wait 500ms max. during EC ops */
>  #define ACPI_EC_UDELAY_GLK	1000	/* Wait 1ms max. to get global lock */
> -#define ACPI_EC_MSI_UDELAY	550	/* Wait 550us for MSI EC */
>  #define ACPI_EC_UDELAY_POLL	1000	/* Wait 1ms for EC transaction polling */
>  #define ACPI_EC_CLEAR_MAX	100	/* Maximum number of events to query
>  					 * when trying to clear the EC */
> @@ -262,12 +261,20 @@ static const char *acpi_ec_cmd_string(u8 cmd)
>   *                           GPE Registers
>   * -------------------------------------------------------------------------- */
> 
> +static inline bool acpi_ec_is_gpe_enabled(struct acpi_ec *ec)
> +{
> +	acpi_event_status gpe_status = 0;
> +
> +	(void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
> +	return (gpe_status & ACPI_EVENT_FLAG_ENABLE_SET) ? true : false;
> +}
> +
>  static inline bool acpi_ec_is_gpe_raised(struct acpi_ec *ec)
>  {
>  	acpi_event_status gpe_status = 0;
> 
>  	(void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
> -	return (gpe_status & ACPI_EVENT_FLAG_SET) ? true : false;
> +	return (gpe_status & ACPI_EVENT_FLAG_STATUS_SET) ? true : false;
>  }
> 
>  static inline void acpi_ec_enable_gpe(struct acpi_ec *ec, bool open)
> @@ -505,9 +512,7 @@ static int ec_poll(struct acpi_ec *ec)
>  		unsigned long usecs = ACPI_EC_UDELAY_POLL;
>  		do {
>  			/* don't sleep with disabled interrupts */
> -			if (EC_FLAGS_MSI || irqs_disabled()) {
> -				usecs = ACPI_EC_MSI_UDELAY;
> -				udelay(usecs);
> +			if (EC_FLAGS_MSI || !acpi_ec_is_gpe_enabled(ec)) {
>  				if (ec_transaction_completed(ec))
>  					return 0;
>  			} else {
> @@ -517,7 +522,9 @@ static int ec_poll(struct acpi_ec *ec)
>  					return 0;
>  			}
>  			spin_lock_irqsave(&ec->lock, flags);
> -			if (time_after(jiffies,
> +			if (EC_FLAGS_MSI ||
> +			    !acpi_ec_is_gpe_enabled(ec) ||
> +			    time_after(jiffies,
>  					ec->curr->timestamp +
>  					usecs_to_jiffies(usecs)))
>  				advance_transaction(ec);
> @@ -537,8 +544,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
>  	unsigned long tmp;
>  	int ret = 0;
> 
> -	if (EC_FLAGS_MSI)
> -		udelay(ACPI_EC_MSI_UDELAY);
>  	/* start transaction */
>  	spin_lock_irqsave(&ec->lock, tmp);
>  	/* Enable GPE for command processing (IBF=0/OBF=1) */
> --
> 1.7.10

Re: [PATCH] ACPI / EC: Improve busy polling quirk.

[Rafael J. Wysocki]

On Wednesday, May 13, 2015 07:25:05 AM Zheng, Lv wrote:
> Hi, Rafael

Hi,

> Since we've implemented register access guarding in the wait polling mode in this commit:
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=9e295ac
> So all udelay() quirks may be no longer necessary and we can remove it.
> I'm asking an original reporter to confirm this:
> https://bugzilla.kernel.org/show_bug.cgi?id=77431
> After removing the udelay() quirk we can turn it to be a special usage model:
> Do busy polling as a non-default behavior using a module param so that it is still useful for debugging.
> 
> This commit cannot reflect all of the above stories and may leave regressions for guarding required platforms.
> Please ignore it and I'll prepare a better patchset for this.

OK, thanks!


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

[PATCH v2 0/6] ACPI / EC: Update due to recent changes.

[Lv Zheng]

This patchset tries to cleanup the EC driver to reflect the recent changes.
There is a small fix in the patchset to use time_before() instead of
time_after().
The last patch removes all non-root-caused MSI quirks so that we may be
able to identify their root cause if regressions are reported against this
removal and generate new quirks based on the new code base.

Lv Zheng (6):
  ACPI / EC: Update acpi_ec_is_gpe_raised() with new GPE status flag.
  ACPI / EC: Remove storming threashold enlarging quirk.
  ACPI / EC: Remove irqs_disabled() check.
  ACPI / EC: Fix and clean up register access guarding logics.
  ACPI / EC: Add module params for polling modes.
  ACPI / EC: Remove non-root-caused busy polling quirks.

 drivers/acpi/ec.c       |  148 ++++++++++++++++++++++-------------------------
 drivers/acpi/internal.h |    1 +
 2 files changed, 69 insertions(+), 80 deletions(-)

-- 
1.7.10

[PATCH v2 0/6] ACPI / EC: Update due to recent changes.

[Lv Zheng]

This patchset tries to cleanup the EC driver to reflect the recent changes.
There is a small fix in the patchset to use time_before() instead of
time_after().
The last patch removes all non-root-caused MSI quirks so that we may be
able to identify their root cause if regressions are reported against this
removal and generate new quirks based on the new code base.

Lv Zheng (6):
  ACPI / EC: Update acpi_ec_is_gpe_raised() with new GPE status flag.
  ACPI / EC: Remove storming threashold enlarging quirk.
  ACPI / EC: Remove irqs_disabled() check.
  ACPI / EC: Fix and clean up register access guarding logics.
  ACPI / EC: Add module params for polling modes.
  ACPI / EC: Remove non-root-caused busy polling quirks.

 drivers/acpi/ec.c       |  148 ++++++++++++++++++++++-------------------------
 drivers/acpi/internal.h |    1 +
 2 files changed, 69 insertions(+), 80 deletions(-)

-- 
1.7.10

[PATCH v2 1/6] ACPI / EC: Update acpi_ec_is_gpe_raised() with new GPE status flag.

[Lv Zheng]

This patch updates acpi_ec_is_gpe_raised() according to the following
commit:
  Commit: 09af8e8290deaff821ced01ea83594ee4c21e8df
  Subject: ACPICA: Events: Add support to return both enable/status register values for GPE and fixed event.
This is actually a no-op change as both the flags are defined to a same
value.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 5e8fed4..99084e8 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -267,7 +267,7 @@ static inline bool acpi_ec_is_gpe_raised(struct acpi_ec *ec)
 	acpi_event_status gpe_status = 0;
 
 	(void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
-	return (gpe_status & ACPI_EVENT_FLAG_SET) ? true : false;
+	return (gpe_status & ACPI_EVENT_FLAG_STATUS_SET) ? true : false;
 }
 
 static inline void acpi_ec_enable_gpe(struct acpi_ec *ec, bool open)
-- 
1.7.10

[PATCH v2 1/6] ACPI / EC: Update acpi_ec_is_gpe_raised() with new GPE status flag.

[Lv Zheng]

This patch updates acpi_ec_is_gpe_raised() according to the following
commit:
  Commit: 09af8e8290deaff821ced01ea83594ee4c21e8df
  Subject: ACPICA: Events: Add support to return both enable/status register values for GPE and fixed event.
This is actually a no-op change as both the flags are defined to a same
value.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 5e8fed4..99084e8 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -267,7 +267,7 @@ static inline bool acpi_ec_is_gpe_raised(struct acpi_ec *ec)
 	acpi_event_status gpe_status = 0;
 
 	(void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
-	return (gpe_status & ACPI_EVENT_FLAG_SET) ? true : false;
+	return (gpe_status & ACPI_EVENT_FLAG_STATUS_SET) ? true : false;
 }
 
 static inline void acpi_ec_enable_gpe(struct acpi_ec *ec, bool open)
-- 
1.7.10

[PATCH v2 2/6] ACPI / EC: Remove storming threashold enlarging quirk.

[Lv Zheng]

This patch removes the storming threashold enlarging quirk.

After applying the following commit, we can notice that there is no no-op
GPE handling invocation can be observed, thus it is unlikely that the
no-op counts can exceed the storming threashold:
  Commit: ca37bfdfbc8d0a3ec73e4b97bb26dcfa51d515aa
  Subject: ACPI / EC: Fix several GPE handling issues by deploying ACPI_GPE_DISPATCH_RAW_HANDLER mode.
Even when the storming happens, we have already limited its affection to
the only transaction and no further transactions will be affected. This is
done by this commit:
  Commit: e1d4d90fc0313d3d58cbd7912c90f8ef24df45ff
  Subject: ACPI / EC: Refine command storm prevention support

So it's time to remove this quirk.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=45151
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 99084e8..170d743 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1247,17 +1247,6 @@ static int ec_flag_msi(const struct dmi_system_id *id)
 }
 
 /*
- * Clevo M720 notebook actually works ok with IRQ mode, if we lifted
- * the GPE storm threshold back to 20
- */
-static int ec_enlarge_storm_threshold(const struct dmi_system_id *id)
-{
-	pr_debug("Setting the EC GPE storm threshold to 20\n");
-	ec_storm_threshold  = 20;
-	return 0;
-}
-
-/*
  * Acer EC firmware refuses to respond QR_EC when SCI_EVT is not set, for
  * which case, we complete the QR_EC without issuing it to the firmware.
  * https://bugzilla.kernel.org/show_bug.cgi?id=86211
@@ -1329,10 +1318,6 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
 	ec_validate_ecdt, "ASUS hardware", {
 	DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTeK Computer Inc.") }, NULL},
 	{
-	ec_enlarge_storm_threshold, "CLEVO hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "CLEVO Co."),
-	DMI_MATCH(DMI_PRODUCT_NAME, "M720T/M730T"),}, NULL},
-	{
 	ec_skip_dsdt_scan, "HP Folio 13", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 	DMI_MATCH(DMI_PRODUCT_NAME, "HP Folio 13"),}, NULL},
-- 
1.7.10

[PATCH v2 2/6] ACPI / EC: Remove storming threashold enlarging quirk.

[Lv Zheng]

This patch removes the storming threashold enlarging quirk.

After applying the following commit, we can notice that there is no no-op
GPE handling invocation can be observed, thus it is unlikely that the
no-op counts can exceed the storming threashold:
  Commit: ca37bfdfbc8d0a3ec73e4b97bb26dcfa51d515aa
  Subject: ACPI / EC: Fix several GPE handling issues by deploying ACPI_GPE_DISPATCH_RAW_HANDLER mode.
Even when the storming happens, we have already limited its affection to
the only transaction and no further transactions will be affected. This is
done by this commit:
  Commit: e1d4d90fc0313d3d58cbd7912c90f8ef24df45ff
  Subject: ACPI / EC: Refine command storm prevention support

So it's time to remove this quirk.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=45151
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 99084e8..170d743 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1247,17 +1247,6 @@ static int ec_flag_msi(const struct dmi_system_id *id)
 }
 
 /*
- * Clevo M720 notebook actually works ok with IRQ mode, if we lifted
- * the GPE storm threshold back to 20
- */
-static int ec_enlarge_storm_threshold(const struct dmi_system_id *id)
-{
-	pr_debug("Setting the EC GPE storm threshold to 20\n");
-	ec_storm_threshold  = 20;
-	return 0;
-}
-
-/*
  * Acer EC firmware refuses to respond QR_EC when SCI_EVT is not set, for
  * which case, we complete the QR_EC without issuing it to the firmware.
  * https://bugzilla.kernel.org/show_bug.cgi?id=86211
@@ -1329,10 +1318,6 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
 	ec_validate_ecdt, "ASUS hardware", {
 	DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTeK Computer Inc.") }, NULL},
 	{
-	ec_enlarge_storm_threshold, "CLEVO hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "CLEVO Co."),
-	DMI_MATCH(DMI_PRODUCT_NAME, "M720T/M730T"),}, NULL},
-	{
 	ec_skip_dsdt_scan, "HP Folio 13", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
 	DMI_MATCH(DMI_PRODUCT_NAME, "HP Folio 13"),}, NULL},
-- 
1.7.10

[PATCH v2 3/6] ACPI / EC: Remove irqs_disabled() check.

[Lv Zheng]

The following commit merges polling and interrupt modes for EC driver:
  Commit: 2a84cb9852f52c0cd1c48bca41a8792d44ad06cc Mon Sep 17 00:00:00 2001
  Subject: ACPI: EC: Merge IRQ and POLL modes
The irqs_disabled() check introduced in it tries to fall into busy polling
mode when the context of ec_poll() cannot sleep.

Actually ec_poll() is ensured to be invoked in the contexts that can sleep
(from a sysfs /sys/kernel/debug/ec/ec0/io access, or from
acpi_evaluate_object(), or from acpi_ec_gpe_poller()). Without the MSI
quirk, we never saw the udelay() logic invoked. Thus this check is useless
and can be removed.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 170d743..20bd43f 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -504,8 +504,7 @@ static int ec_poll(struct acpi_ec *ec)
 			msecs_to_jiffies(ec_delay);
 		unsigned long usecs = ACPI_EC_UDELAY_POLL;
 		do {
-			/* don't sleep with disabled interrupts */
-			if (EC_FLAGS_MSI || irqs_disabled()) {
+			if (EC_FLAGS_MSI) {
 				usecs = ACPI_EC_MSI_UDELAY;
 				udelay(usecs);
 				if (ec_transaction_completed(ec))
-- 
1.7.10

[PATCH v2 3/6] ACPI / EC: Remove irqs_disabled() check.

[Lv Zheng]

The following commit merges polling and interrupt modes for EC driver:
  Commit: 2a84cb9852f52c0cd1c48bca41a8792d44ad06cc Mon Sep 17 00:00:00 2001
  Subject: ACPI: EC: Merge IRQ and POLL modes
The irqs_disabled() check introduced in it tries to fall into busy polling
mode when the context of ec_poll() cannot sleep.

Actually ec_poll() is ensured to be invoked in the contexts that can sleep
(from a sysfs /sys/kernel/debug/ec/ec0/io access, or from
acpi_evaluate_object(), or from acpi_ec_gpe_poller()). Without the MSI
quirk, we never saw the udelay() logic invoked. Thus this check is useless
and can be removed.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 170d743..20bd43f 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -504,8 +504,7 @@ static int ec_poll(struct acpi_ec *ec)
 			msecs_to_jiffies(ec_delay);
 		unsigned long usecs = ACPI_EC_UDELAY_POLL;
 		do {
-			/* don't sleep with disabled interrupts */
-			if (EC_FLAGS_MSI || irqs_disabled()) {
+			if (EC_FLAGS_MSI) {
 				usecs = ACPI_EC_MSI_UDELAY;
 				udelay(usecs);
 				if (ec_transaction_completed(ec))
-- 
1.7.10

[PATCH v2 4/6] ACPI / EC: Fix and clean up register access guarding logics.

[Lv Zheng]

In the polling mode, EC driver shouldn't access the EC registers too
frequently. Though this statement is concluded from the non-root caused
bugs (see links below), we've maintained the register access guarding
logics in the current EC driver. The guarding logics can be found here and
there, makes it hard to root cause real timing issues. This patch collects
the guarding logics into one single function so that all hidden logics
related to this can be seen clearly.

The current guarding related code also has several issues:
1. Per-transaction timestamp prevents inter-transaction guarding from being
   implemented in the same place. We have an inter-transaction udelay() in
   acpi_ec_transaction_unblocked(), this logic can be merged into ec_poll()
   if we can use per-device timestamp. This patch completes such merge to
   form a new ec_guard() function and collects all guarding related hidden
   logics in it.
   One hidden logic is: there is no inter-transaction guarding performed
   for non MSI quirk (wait polling mode), this patch skips
   inter-transaction guarding before wait_event_timeout() for the wait
   polling mode to reveal the hidden logic.
   The other hidden logic is: there is msleep() inter-transaction guarding
   performed when the GPE storming is observed. As after merging this
   commit:
     Commit: e1d4d90fc0313d3d58cbd7912c90f8ef24df45ff
     Subject: ACPI / EC: Refine command storm prevention support
   EC_FLAGS_COMMAND_STORM is ensured to be cleared after invoking
   acpi_ec_transaction_unlocked(), the msleep() guard logic will never
   happen now. Since no one complains such change, this logic is likely
   added during the old times where the EC race issues are not fixed and
   the bugs are false root-caused to the timing issue. This patch simply
   removes the out-dated logic. We can restore it by stop skipping
   inter-transaction guarding for wait polling mode.
   Two different delay values are defined for msleep() and udelay() while
   they are merged in this patch to 550us.
2. time_after() causes additional delay in the polling mode (can only be
   observed in noirq suspend/resume processes where polling mode is always
   used) before advance_transaction() is invoked ("wait polling" log is
   added before wait_event_timeout()). We can see 2 wait_event_timeout()
   invocations. This is because time_after() ensures a ">" validation while
   we only need a ">=" validation here:
   [   86.739909] ACPI: Waking up from system sleep state S3
   [   86.742857] ACPI : EC: 2: Increase command
   [   86.742859] ACPI : EC: ***** Command(RD_EC) started *****
   [   86.742861] ACPI : EC: ===== TASK (0) =====
   [   86.742871] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   86.742873] ACPI : EC: EC_SC(W) = 0x80
   [   86.742876] ACPI : EC: ***** Event started *****
   [   86.742880] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.743972] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.747966] ACPI : EC: ===== TASK (0) =====
   [   86.747977] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   86.747978] ACPI : EC: EC_DATA(W) = 0x06
   [   86.747981] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.751971] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.755969] ACPI : EC: ===== TASK (0) =====
   [   86.755991] ACPI : EC: EC_SC(R) = 0x21 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=1
   [   86.755993] ACPI : EC: EC_DATA(R) = 0x03
   [   86.755994] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.755995] ACPI : EC: ***** Command(RD_EC) stopped *****
   [   86.755996] ACPI : EC: 1: Decrease command
   This patch corrects this by using time_before() instead in ec_guard():
   [   54.283146] ACPI: Waking up from system sleep state S3
   [   54.285414] ACPI : EC: 2: Increase command
   [   54.285415] ACPI : EC: ***** Command(RD_EC) started *****
   [   54.285416] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.285417] ACPI : EC: ===== TASK (0) =====
   [   54.285424] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   54.285425] ACPI : EC: EC_SC(W) = 0x80
   [   54.285427] ACPI : EC: ***** Event started *****
   [   54.285429] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.287209] ACPI : EC: ===== TASK (0) =====
   [   54.287218] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   54.287219] ACPI : EC: EC_DATA(W) = 0x06
   [   54.287222] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.291190] ACPI : EC: ===== TASK (0) =====
   [   54.291210] ACPI : EC: EC_SC(R) = 0x21 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=1
   [   54.291213] ACPI : EC: EC_DATA(R) = 0x03
   [   54.291214] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.291215] ACPI : EC: ***** Command(RD_EC) stopped *****
   [   54.291216] ACPI : EC: 1: Decrease command

After cleaning up all guarding logics, we have one single function
ec_guard() collecting all old, non-root-caused, hidden logics. Then we can
easily tune the logics in one place to respond to the bug reports.

Except the time_before() change, all other changes do not change the
behavior of the EC driver.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=12011
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=20242
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=77431
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c       |   82 +++++++++++++++++++++++++++++++----------------
 drivers/acpi/internal.h |    1 +
 2 files changed, 55 insertions(+), 28 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 20bd43f..a521b6b 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -70,8 +70,7 @@ enum ec_command {
 
 #define ACPI_EC_DELAY		500	/* Wait 500ms max. during EC ops */
 #define ACPI_EC_UDELAY_GLK	1000	/* Wait 1ms max. to get global lock */
-#define ACPI_EC_MSI_UDELAY	550	/* Wait 550us for MSI EC */
-#define ACPI_EC_UDELAY_POLL	1000	/* Wait 1ms for EC transaction polling */
+#define ACPI_EC_UDELAY_POLL	550	/* Wait 1ms for EC transaction polling */
 #define ACPI_EC_CLEAR_MAX	100	/* Maximum number of events to query
 					 * when trying to clear the EC */
 
@@ -121,7 +120,6 @@ struct transaction {
 	u8 wlen;
 	u8 rlen;
 	u8 flags;
-	unsigned long timestamp;
 };
 
 static int acpi_ec_query(struct acpi_ec *ec, u8 *data);
@@ -218,7 +216,7 @@ static inline u8 acpi_ec_read_data(struct acpi_ec *ec)
 {
 	u8 x = inb(ec->data_addr);
 
-	ec->curr->timestamp = jiffies;
+	ec->timestamp = jiffies;
 	ec_dbg_raw("EC_DATA(R) = 0x%2.2x", x);
 	return x;
 }
@@ -227,14 +225,14 @@ static inline void acpi_ec_write_cmd(struct acpi_ec *ec, u8 command)
 {
 	ec_dbg_raw("EC_SC(W) = 0x%2.2x", command);
 	outb(command, ec->command_addr);
-	ec->curr->timestamp = jiffies;
+	ec->timestamp = jiffies;
 }
 
 static inline void acpi_ec_write_data(struct acpi_ec *ec, u8 data)
 {
 	ec_dbg_raw("EC_DATA(W) = 0x%2.2x", data);
 	outb(data, ec->data_addr);
-	ec->curr->timestamp = jiffies;
+	ec->timestamp = jiffies;
 }
 
 #ifdef DEBUG
@@ -392,6 +390,18 @@ static void acpi_ec_complete_query(struct acpi_ec *ec)
 	}
 }
 
+static int ec_transaction_polled(struct acpi_ec *ec)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&ec->lock, flags);
+	if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_POLL))
+		ret = 1;
+	spin_unlock_irqrestore(&ec->lock, flags);
+	return ret;
+}
+
 static int ec_transaction_completed(struct acpi_ec *ec)
 {
 	unsigned long flags;
@@ -490,8 +500,37 @@ static void start_transaction(struct acpi_ec *ec)
 {
 	ec->curr->irq_count = ec->curr->wi = ec->curr->ri = 0;
 	ec->curr->flags = 0;
-	ec->curr->timestamp = jiffies;
-	advance_transaction(ec);
+}
+
+static int ec_guard(struct acpi_ec *ec)
+{
+	unsigned long guard = usecs_to_jiffies(ACPI_EC_UDELAY_POLL);
+	unsigned long timeout = ec->timestamp + guard;
+
+	do {
+		if (EC_FLAGS_MSI) {
+			/* Perform busy polling */
+			if (ec_transaction_completed(ec))
+				return 0;
+			udelay(jiffies_to_usecs(guard));
+		} else {
+			/*
+			 * Perform wait polling
+			 *
+			 * The following check is there to keep the old
+			 * logic - no inter-transaction guarding for the
+			 * wait polling mode.
+			 */
+			if (!ec_transaction_polled(ec))
+				break;
+			if (wait_event_timeout(ec->wait,
+					       ec_transaction_completed(ec),
+					       guard))
+				return 0;
+		}
+		/* Guard the register accesses for the polling modes */
+	} while (time_before(jiffies, timeout));
+	return -ETIME;
 }
 
 static int ec_poll(struct acpi_ec *ec)
@@ -502,24 +541,11 @@ static int ec_poll(struct acpi_ec *ec)
 	while (repeat--) {
 		unsigned long delay = jiffies +
 			msecs_to_jiffies(ec_delay);
-		unsigned long usecs = ACPI_EC_UDELAY_POLL;
 		do {
-			if (EC_FLAGS_MSI) {
-				usecs = ACPI_EC_MSI_UDELAY;
-				udelay(usecs);
-				if (ec_transaction_completed(ec))
-					return 0;
-			} else {
-				if (wait_event_timeout(ec->wait,
-						ec_transaction_completed(ec),
-						usecs_to_jiffies(usecs)))
-					return 0;
-			}
+			if (!ec_guard(ec))
+				return 0;
 			spin_lock_irqsave(&ec->lock, flags);
-			if (time_after(jiffies,
-					ec->curr->timestamp +
-					usecs_to_jiffies(usecs)))
-				advance_transaction(ec);
+			advance_transaction(ec);
 			spin_unlock_irqrestore(&ec->lock, flags);
 		} while (time_before(jiffies, delay));
 		pr_debug("controller reset, restart transaction\n");
@@ -536,8 +562,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	unsigned long tmp;
 	int ret = 0;
 
-	if (EC_FLAGS_MSI)
-		udelay(ACPI_EC_MSI_UDELAY);
 	/* start transaction */
 	spin_lock_irqsave(&ec->lock, tmp);
 	/* Enable GPE for command processing (IBF=0/OBF=1) */
@@ -551,7 +575,9 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	ec_dbg_req("Command(%s) started", acpi_ec_cmd_string(t->command));
 	start_transaction(ec);
 	spin_unlock_irqrestore(&ec->lock, tmp);
+
 	ret = ec_poll(ec);
+
 	spin_lock_irqsave(&ec->lock, tmp);
 	if (t->irq_count == ec_storm_threshold)
 		acpi_ec_clear_storm(ec, EC_FLAGS_COMMAND_STORM);
@@ -574,6 +600,7 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 		return -EINVAL;
 	if (t->rdata)
 		memset(t->rdata, 0, t->rlen);
+
 	mutex_lock(&ec->mutex);
 	if (ec->global_lock) {
 		status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
@@ -585,8 +612,6 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 
 	status = acpi_ec_transaction_unlocked(ec, t);
 
-	if (test_bit(EC_FLAGS_COMMAND_STORM, &ec->flags))
-		msleep(1);
 	if (ec->global_lock)
 		acpi_release_global_lock(glk);
 unlock:
@@ -1002,6 +1027,7 @@ static struct acpi_ec *make_acpi_ec(void)
 	INIT_LIST_HEAD(&ec->list);
 	spin_lock_init(&ec->lock);
 	INIT_WORK(&ec->work, acpi_ec_gpe_poller);
+	ec->timestamp = jiffies;
 	return ec;
 }
 
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index ba4a61e..61cb506 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -138,6 +138,7 @@ struct acpi_ec {
 	struct transaction *curr;
 	spinlock_t lock;
 	struct work_struct work;
+	unsigned long timestamp;
 };
 
 extern struct acpi_ec *first_ec;
-- 
1.7.10

[PATCH v2 4/6] ACPI / EC: Fix and clean up register access guarding logics.

[Lv Zheng]

In the polling mode, EC driver shouldn't access the EC registers too
frequently. Though this statement is concluded from the non-root caused
bugs (see links below), we've maintained the register access guarding
logics in the current EC driver. The guarding logics can be found here and
there, makes it hard to root cause real timing issues. This patch collects
the guarding logics into one single function so that all hidden logics
related to this can be seen clearly.

The current guarding related code also has several issues:
1. Per-transaction timestamp prevents inter-transaction guarding from being
   implemented in the same place. We have an inter-transaction udelay() in
   acpi_ec_transaction_unblocked(), this logic can be merged into ec_poll()
   if we can use per-device timestamp. This patch completes such merge to
   form a new ec_guard() function and collects all guarding related hidden
   logics in it.
   One hidden logic is: there is no inter-transaction guarding performed
   for non MSI quirk (wait polling mode), this patch skips
   inter-transaction guarding before wait_event_timeout() for the wait
   polling mode to reveal the hidden logic.
   The other hidden logic is: there is msleep() inter-transaction guarding
   performed when the GPE storming is observed. As after merging this
   commit:
     Commit: e1d4d90fc0313d3d58cbd7912c90f8ef24df45ff
     Subject: ACPI / EC: Refine command storm prevention support
   EC_FLAGS_COMMAND_STORM is ensured to be cleared after invoking
   acpi_ec_transaction_unlocked(), the msleep() guard logic will never
   happen now. Since no one complains such change, this logic is likely
   added during the old times where the EC race issues are not fixed and
   the bugs are false root-caused to the timing issue. This patch simply
   removes the out-dated logic. We can restore it by stop skipping
   inter-transaction guarding for wait polling mode.
   Two different delay values are defined for msleep() and udelay() while
   they are merged in this patch to 550us.
2. time_after() causes additional delay in the polling mode (can only be
   observed in noirq suspend/resume processes where polling mode is always
   used) before advance_transaction() is invoked ("wait polling" log is
   added before wait_event_timeout()). We can see 2 wait_event_timeout()
   invocations. This is because time_after() ensures a ">" validation while
   we only need a ">=" validation here:
   [   86.739909] ACPI: Waking up from system sleep state S3
   [   86.742857] ACPI : EC: 2: Increase command
   [   86.742859] ACPI : EC: ***** Command(RD_EC) started *****
   [   86.742861] ACPI : EC: ===== TASK (0) =====
   [   86.742871] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   86.742873] ACPI : EC: EC_SC(W) = 0x80
   [   86.742876] ACPI : EC: ***** Event started *****
   [   86.742880] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.743972] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.747966] ACPI : EC: ===== TASK (0) =====
   [   86.747977] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   86.747978] ACPI : EC: EC_DATA(W) = 0x06
   [   86.747981] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.751971] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.755969] ACPI : EC: ===== TASK (0) =====
   [   86.755991] ACPI : EC: EC_SC(R) = 0x21 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=1
   [   86.755993] ACPI : EC: EC_DATA(R) = 0x03
   [   86.755994] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   86.755995] ACPI : EC: ***** Command(RD_EC) stopped *****
   [   86.755996] ACPI : EC: 1: Decrease command
   This patch corrects this by using time_before() instead in ec_guard():
   [   54.283146] ACPI: Waking up from system sleep state S3
   [   54.285414] ACPI : EC: 2: Increase command
   [   54.285415] ACPI : EC: ***** Command(RD_EC) started *****
   [   54.285416] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.285417] ACPI : EC: ===== TASK (0) =====
   [   54.285424] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   54.285425] ACPI : EC: EC_SC(W) = 0x80
   [   54.285427] ACPI : EC: ***** Event started *****
   [   54.285429] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.287209] ACPI : EC: ===== TASK (0) =====
   [   54.287218] ACPI : EC: EC_SC(R) = 0x20 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=0
   [   54.287219] ACPI : EC: EC_DATA(W) = 0x06
   [   54.287222] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.291190] ACPI : EC: ===== TASK (0) =====
   [   54.291210] ACPI : EC: EC_SC(R) = 0x21 SCI_EVT=1 BURST=0 CMD=0 IBF=0 OBF=1
   [   54.291213] ACPI : EC: EC_DATA(R) = 0x03
   [   54.291214] ACPI : EC: ~~~~~ wait polling ~~~~~
   [   54.291215] ACPI : EC: ***** Command(RD_EC) stopped *****
   [   54.291216] ACPI : EC: 1: Decrease command

After cleaning up all guarding logics, we have one single function
ec_guard() collecting all old, non-root-caused, hidden logics. Then we can
easily tune the logics in one place to respond to the bug reports.

Except the time_before() change, all other changes do not change the
behavior of the EC driver.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=12011
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=20242
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=77431
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c       |   82 +++++++++++++++++++++++++++++++----------------
 drivers/acpi/internal.h |    1 +
 2 files changed, 55 insertions(+), 28 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 20bd43f..a521b6b 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -70,8 +70,7 @@ enum ec_command {
 
 #define ACPI_EC_DELAY		500	/* Wait 500ms max. during EC ops */
 #define ACPI_EC_UDELAY_GLK	1000	/* Wait 1ms max. to get global lock */
-#define ACPI_EC_MSI_UDELAY	550	/* Wait 550us for MSI EC */
-#define ACPI_EC_UDELAY_POLL	1000	/* Wait 1ms for EC transaction polling */
+#define ACPI_EC_UDELAY_POLL	550	/* Wait 1ms for EC transaction polling */
 #define ACPI_EC_CLEAR_MAX	100	/* Maximum number of events to query
 					 * when trying to clear the EC */
 
@@ -121,7 +120,6 @@ struct transaction {
 	u8 wlen;
 	u8 rlen;
 	u8 flags;
-	unsigned long timestamp;
 };
 
 static int acpi_ec_query(struct acpi_ec *ec, u8 *data);
@@ -218,7 +216,7 @@ static inline u8 acpi_ec_read_data(struct acpi_ec *ec)
 {
 	u8 x = inb(ec->data_addr);
 
-	ec->curr->timestamp = jiffies;
+	ec->timestamp = jiffies;
 	ec_dbg_raw("EC_DATA(R) = 0x%2.2x", x);
 	return x;
 }
@@ -227,14 +225,14 @@ static inline void acpi_ec_write_cmd(struct acpi_ec *ec, u8 command)
 {
 	ec_dbg_raw("EC_SC(W) = 0x%2.2x", command);
 	outb(command, ec->command_addr);
-	ec->curr->timestamp = jiffies;
+	ec->timestamp = jiffies;
 }
 
 static inline void acpi_ec_write_data(struct acpi_ec *ec, u8 data)
 {
 	ec_dbg_raw("EC_DATA(W) = 0x%2.2x", data);
 	outb(data, ec->data_addr);
-	ec->curr->timestamp = jiffies;
+	ec->timestamp = jiffies;
 }
 
 #ifdef DEBUG
@@ -392,6 +390,18 @@ static void acpi_ec_complete_query(struct acpi_ec *ec)
 	}
 }
 
+static int ec_transaction_polled(struct acpi_ec *ec)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&ec->lock, flags);
+	if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_POLL))
+		ret = 1;
+	spin_unlock_irqrestore(&ec->lock, flags);
+	return ret;
+}
+
 static int ec_transaction_completed(struct acpi_ec *ec)
 {
 	unsigned long flags;
@@ -490,8 +500,37 @@ static void start_transaction(struct acpi_ec *ec)
 {
 	ec->curr->irq_count = ec->curr->wi = ec->curr->ri = 0;
 	ec->curr->flags = 0;
-	ec->curr->timestamp = jiffies;
-	advance_transaction(ec);
+}
+
+static int ec_guard(struct acpi_ec *ec)
+{
+	unsigned long guard = usecs_to_jiffies(ACPI_EC_UDELAY_POLL);
+	unsigned long timeout = ec->timestamp + guard;
+
+	do {
+		if (EC_FLAGS_MSI) {
+			/* Perform busy polling */
+			if (ec_transaction_completed(ec))
+				return 0;
+			udelay(jiffies_to_usecs(guard));
+		} else {
+			/*
+			 * Perform wait polling
+			 *
+			 * The following check is there to keep the old
+			 * logic - no inter-transaction guarding for the
+			 * wait polling mode.
+			 */
+			if (!ec_transaction_polled(ec))
+				break;
+			if (wait_event_timeout(ec->wait,
+					       ec_transaction_completed(ec),
+					       guard))
+				return 0;
+		}
+		/* Guard the register accesses for the polling modes */
+	} while (time_before(jiffies, timeout));
+	return -ETIME;
 }
 
 static int ec_poll(struct acpi_ec *ec)
@@ -502,24 +541,11 @@ static int ec_poll(struct acpi_ec *ec)
 	while (repeat--) {
 		unsigned long delay = jiffies +
 			msecs_to_jiffies(ec_delay);
-		unsigned long usecs = ACPI_EC_UDELAY_POLL;
 		do {
-			if (EC_FLAGS_MSI) {
-				usecs = ACPI_EC_MSI_UDELAY;
-				udelay(usecs);
-				if (ec_transaction_completed(ec))
-					return 0;
-			} else {
-				if (wait_event_timeout(ec->wait,
-						ec_transaction_completed(ec),
-						usecs_to_jiffies(usecs)))
-					return 0;
-			}
+			if (!ec_guard(ec))
+				return 0;
 			spin_lock_irqsave(&ec->lock, flags);
-			if (time_after(jiffies,
-					ec->curr->timestamp +
-					usecs_to_jiffies(usecs)))
-				advance_transaction(ec);
+			advance_transaction(ec);
 			spin_unlock_irqrestore(&ec->lock, flags);
 		} while (time_before(jiffies, delay));
 		pr_debug("controller reset, restart transaction\n");
@@ -536,8 +562,6 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	unsigned long tmp;
 	int ret = 0;
 
-	if (EC_FLAGS_MSI)
-		udelay(ACPI_EC_MSI_UDELAY);
 	/* start transaction */
 	spin_lock_irqsave(&ec->lock, tmp);
 	/* Enable GPE for command processing (IBF=0/OBF=1) */
@@ -551,7 +575,9 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	ec_dbg_req("Command(%s) started", acpi_ec_cmd_string(t->command));
 	start_transaction(ec);
 	spin_unlock_irqrestore(&ec->lock, tmp);
+
 	ret = ec_poll(ec);
+
 	spin_lock_irqsave(&ec->lock, tmp);
 	if (t->irq_count == ec_storm_threshold)
 		acpi_ec_clear_storm(ec, EC_FLAGS_COMMAND_STORM);
@@ -574,6 +600,7 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 		return -EINVAL;
 	if (t->rdata)
 		memset(t->rdata, 0, t->rlen);
+
 	mutex_lock(&ec->mutex);
 	if (ec->global_lock) {
 		status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
@@ -585,8 +612,6 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 
 	status = acpi_ec_transaction_unlocked(ec, t);
 
-	if (test_bit(EC_FLAGS_COMMAND_STORM, &ec->flags))
-		msleep(1);
 	if (ec->global_lock)
 		acpi_release_global_lock(glk);
 unlock:
@@ -1002,6 +1027,7 @@ static struct acpi_ec *make_acpi_ec(void)
 	INIT_LIST_HEAD(&ec->list);
 	spin_lock_init(&ec->lock);
 	INIT_WORK(&ec->work, acpi_ec_gpe_poller);
+	ec->timestamp = jiffies;
 	return ec;
 }
 
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index ba4a61e..61cb506 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -138,6 +138,7 @@ struct acpi_ec {
 	struct transaction *curr;
 	spinlock_t lock;
 	struct work_struct work;
+	unsigned long timestamp;
 };
 
 extern struct acpi_ec *first_ec;
-- 
1.7.10

[PATCH v2 5/6] ACPI / EC: Add module params for polling modes.

[Lv Zheng]

We have 2 polling modes in the EC driver:
1. busy polling: originally used for the MSI quirks. udelay() is used to
   perform register access guarding.
2. wait polling: normal code path uses wait_event_timeout() and it can be
   woken up as soon as the transaction is completed in the interrupt mode.
   It also contains the register acces guarding logic in case the interrupt
   doesn't arrive and the EC driver is about to advance the transaction in
   task context (the polling mode).
The wait polling is useful for interrupt mode to allow other tasks to use
the CPU during the wait.
But for the polling mode, the busy polling takes less time than the wait
polling, because if no interrupt arrives, the wait polling has to wait the
minimal HZ interval.

We have a new use case for using the busy polling mode. Some GPIO drivers
initialize PIN configuration which cause a GPIO multiplexed EC GPE to be
disabled out of the GPE register's control. Busy polling mode is useful
here as it takes less time than the wait polling. But the guarding logic
prevents it from responding even faster. We should spinning around the EC
status rather than spinning around the nop execution lasted a determined
period.

This patch introduces 2 module params for the polling mode switch and the
guard time, so that users can use the busy polling mode without the
guarding in case the guarding is not necessary. This is an example to use
the 2 module params for this purpose:
  acpi.ec_busy_polling acpi.ec_polling_guard=0

We've tested the patch on a test platform. The platform suffers from such
kind of the GPIO PIN issue. The GPIO driver resets all PIN configuration
and after that, EC interrupt cannot arrive because of the multiplexing.
Then the platform suffers from a long delay carried out by the
wait_event_timeout() as all further EC transactions will run in the polling
mode. We switched the EC driver to use the busy polling mechanism instead
of the wait timeout polling mechanism and the delay is still high:
[   44.283005] calling  PNP0C0B:00+ @ 1305, parent: platform
[   44.417548] call PNP0C0B:00+ returned 0 after 131323 usecs
And this patch can significantly reduce the delay:
[   44.502625] calling  PNP0C0B:00+ @ 1308, parent: platform
[   44.503760] call PNP0C0B:00+ returned 0 after 1103 usecs

Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index a521b6b..846e0617 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -92,6 +92,14 @@ static unsigned int ec_delay __read_mostly = ACPI_EC_DELAY;
 module_param(ec_delay, uint, 0644);
 MODULE_PARM_DESC(ec_delay, "Timeout(ms) waited until an EC command completes");
 
+static bool ec_busy_polling __read_mostly;
+module_param(ec_busy_polling, bool, 0644);
+MODULE_PARM_DESC(ec_busy_polling, "Use busy polling to advance EC transaction");
+
+static unsigned int ec_polling_guard __read_mostly = ACPI_EC_UDELAY_POLL;
+module_param(ec_polling_guard, uint, 0644);
+MODULE_PARM_DESC(ec_polling_guard, "Guard time(us) between EC accesses in polling modes");
+
 /*
  * If the number of false interrupts per one transaction exceeds
  * this threshold, will think there is a GPE storm happened and
@@ -128,7 +136,6 @@ static void advance_transaction(struct acpi_ec *ec);
 struct acpi_ec *boot_ec, *first_ec;
 EXPORT_SYMBOL(first_ec);
 
-static int EC_FLAGS_MSI; /* Out-of-spec MSI controller */
 static int EC_FLAGS_VALIDATE_ECDT; /* ASUStec ECDTs need to be validated */
 static int EC_FLAGS_SKIP_DSDT_SCAN; /* Not all BIOS survive early DSDT scan */
 static int EC_FLAGS_CLEAR_ON_RESUME; /* Needs acpi_ec_clear() on boot/resume */
@@ -504,11 +511,11 @@ static void start_transaction(struct acpi_ec *ec)
 
 static int ec_guard(struct acpi_ec *ec)
 {
-	unsigned long guard = usecs_to_jiffies(ACPI_EC_UDELAY_POLL);
+	unsigned long guard = usecs_to_jiffies(ec_polling_guard);
 	unsigned long timeout = ec->timestamp + guard;
 
 	do {
-		if (EC_FLAGS_MSI) {
+		if (ec_busy_polling) {
 			/* Perform busy polling */
 			if (ec_transaction_completed(ec))
 				return 0;
@@ -985,7 +992,7 @@ acpi_ec_space_handler(u32 function, acpi_physical_address address,
 	if (function != ACPI_READ && function != ACPI_WRITE)
 		return AE_BAD_PARAMETER;
 
-	if (EC_FLAGS_MSI || bits > 8)
+	if (ec_busy_polling || bits > 8)
 		acpi_ec_burst_enable(ec);
 
 	for (i = 0; i < bytes; ++i, ++address, ++value)
@@ -993,7 +1000,7 @@ acpi_ec_space_handler(u32 function, acpi_physical_address address,
 			acpi_ec_read(ec, address, value) :
 			acpi_ec_write(ec, address, *value);
 
-	if (EC_FLAGS_MSI || bits > 8)
+	if (ec_busy_polling || bits > 8)
 		acpi_ec_burst_disable(ec);
 
 	switch (result) {
@@ -1262,11 +1269,11 @@ static int ec_validate_ecdt(const struct dmi_system_id *id)
 	return 0;
 }
 
-/* MSI EC needs special treatment, enable it */
-static int ec_flag_msi(const struct dmi_system_id *id)
+/* EC firmware needs special polling mode, enable it */
+static int ec_use_busy_polling(const struct dmi_system_id *id)
 {
-	pr_debug("Detected MSI hardware, enabling workarounds.\n");
-	EC_FLAGS_MSI = 1;
+	pr_debug("Detected the EC firmware requiring busy polling mode.\n");
+	ec_busy_polling = 1;
 	EC_FLAGS_VALIDATE_ECDT = 1;
 	return 0;
 }
@@ -1313,27 +1320,27 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
 	DMI_MATCH(DMI_BIOS_VENDOR, "COMPAL"),
 	DMI_MATCH(DMI_BOARD_NAME, "JFL92") }, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_BIOS_VENDOR, "Micro-Star")}, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star")}, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-Star")}, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-STAR")}, NULL},
 	{
-	ec_flag_msi, "Quanta hardware", {
+	ec_use_busy_polling, "Quanta hardware", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
 	DMI_MATCH(DMI_PRODUCT_NAME, "TW8/SW8/DW8"),}, NULL},
 	{
-	ec_flag_msi, "Quanta hardware", {
+	ec_use_busy_polling, "Quanta hardware", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
 	DMI_MATCH(DMI_PRODUCT_NAME, "TW9/SW9"),}, NULL},
 	{
-	ec_flag_msi, "Clevo W350etq", {
+	ec_use_busy_polling, "Clevo W350etq", {
 	DMI_MATCH(DMI_SYS_VENDOR, "CLEVO CO."),
 	DMI_MATCH(DMI_PRODUCT_NAME, "W35_37ET"),}, NULL},
 	{
-- 
1.7.10

[PATCH v2 5/6] ACPI / EC: Add module params for polling modes.

[Lv Zheng]

We have 2 polling modes in the EC driver:
1. busy polling: originally used for the MSI quirks. udelay() is used to
   perform register access guarding.
2. wait polling: normal code path uses wait_event_timeout() and it can be
   woken up as soon as the transaction is completed in the interrupt mode.
   It also contains the register acces guarding logic in case the interrupt
   doesn't arrive and the EC driver is about to advance the transaction in
   task context (the polling mode).
The wait polling is useful for interrupt mode to allow other tasks to use
the CPU during the wait.
But for the polling mode, the busy polling takes less time than the wait
polling, because if no interrupt arrives, the wait polling has to wait the
minimal HZ interval.

We have a new use case for using the busy polling mode. Some GPIO drivers
initialize PIN configuration which cause a GPIO multiplexed EC GPE to be
disabled out of the GPE register's control. Busy polling mode is useful
here as it takes less time than the wait polling. But the guarding logic
prevents it from responding even faster. We should spinning around the EC
status rather than spinning around the nop execution lasted a determined
period.

This patch introduces 2 module params for the polling mode switch and the
guard time, so that users can use the busy polling mode without the
guarding in case the guarding is not necessary. This is an example to use
the 2 module params for this purpose:
  acpi.ec_busy_polling acpi.ec_polling_guard=0

We've tested the patch on a test platform. The platform suffers from such
kind of the GPIO PIN issue. The GPIO driver resets all PIN configuration
and after that, EC interrupt cannot arrive because of the multiplexing.
Then the platform suffers from a long delay carried out by the
wait_event_timeout() as all further EC transactions will run in the polling
mode. We switched the EC driver to use the busy polling mechanism instead
of the wait timeout polling mechanism and the delay is still high:
[   44.283005] calling  PNP0C0B:00+ @ 1305, parent: platform
[   44.417548] call PNP0C0B:00+ returned 0 after 131323 usecs
And this patch can significantly reduce the delay:
[   44.502625] calling  PNP0C0B:00+ @ 1308, parent: platform
[   44.503760] call PNP0C0B:00+ returned 0 after 1103 usecs

Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index a521b6b..846e0617 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -92,6 +92,14 @@ static unsigned int ec_delay __read_mostly = ACPI_EC_DELAY;
 module_param(ec_delay, uint, 0644);
 MODULE_PARM_DESC(ec_delay, "Timeout(ms) waited until an EC command completes");
 
+static bool ec_busy_polling __read_mostly;
+module_param(ec_busy_polling, bool, 0644);
+MODULE_PARM_DESC(ec_busy_polling, "Use busy polling to advance EC transaction");
+
+static unsigned int ec_polling_guard __read_mostly = ACPI_EC_UDELAY_POLL;
+module_param(ec_polling_guard, uint, 0644);
+MODULE_PARM_DESC(ec_polling_guard, "Guard time(us) between EC accesses in polling modes");
+
 /*
  * If the number of false interrupts per one transaction exceeds
  * this threshold, will think there is a GPE storm happened and
@@ -128,7 +136,6 @@ static void advance_transaction(struct acpi_ec *ec);
 struct acpi_ec *boot_ec, *first_ec;
 EXPORT_SYMBOL(first_ec);
 
-static int EC_FLAGS_MSI; /* Out-of-spec MSI controller */
 static int EC_FLAGS_VALIDATE_ECDT; /* ASUStec ECDTs need to be validated */
 static int EC_FLAGS_SKIP_DSDT_SCAN; /* Not all BIOS survive early DSDT scan */
 static int EC_FLAGS_CLEAR_ON_RESUME; /* Needs acpi_ec_clear() on boot/resume */
@@ -504,11 +511,11 @@ static void start_transaction(struct acpi_ec *ec)
 
 static int ec_guard(struct acpi_ec *ec)
 {
-	unsigned long guard = usecs_to_jiffies(ACPI_EC_UDELAY_POLL);
+	unsigned long guard = usecs_to_jiffies(ec_polling_guard);
 	unsigned long timeout = ec->timestamp + guard;
 
 	do {
-		if (EC_FLAGS_MSI) {
+		if (ec_busy_polling) {
 			/* Perform busy polling */
 			if (ec_transaction_completed(ec))
 				return 0;
@@ -985,7 +992,7 @@ acpi_ec_space_handler(u32 function, acpi_physical_address address,
 	if (function != ACPI_READ && function != ACPI_WRITE)
 		return AE_BAD_PARAMETER;
 
-	if (EC_FLAGS_MSI || bits > 8)
+	if (ec_busy_polling || bits > 8)
 		acpi_ec_burst_enable(ec);
 
 	for (i = 0; i < bytes; ++i, ++address, ++value)
@@ -993,7 +1000,7 @@ acpi_ec_space_handler(u32 function, acpi_physical_address address,
 			acpi_ec_read(ec, address, value) :
 			acpi_ec_write(ec, address, *value);
 
-	if (EC_FLAGS_MSI || bits > 8)
+	if (ec_busy_polling || bits > 8)
 		acpi_ec_burst_disable(ec);
 
 	switch (result) {
@@ -1262,11 +1269,11 @@ static int ec_validate_ecdt(const struct dmi_system_id *id)
 	return 0;
 }
 
-/* MSI EC needs special treatment, enable it */
-static int ec_flag_msi(const struct dmi_system_id *id)
+/* EC firmware needs special polling mode, enable it */
+static int ec_use_busy_polling(const struct dmi_system_id *id)
 {
-	pr_debug("Detected MSI hardware, enabling workarounds.\n");
-	EC_FLAGS_MSI = 1;
+	pr_debug("Detected the EC firmware requiring busy polling mode.\n");
+	ec_busy_polling = 1;
 	EC_FLAGS_VALIDATE_ECDT = 1;
 	return 0;
 }
@@ -1313,27 +1320,27 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
 	DMI_MATCH(DMI_BIOS_VENDOR, "COMPAL"),
 	DMI_MATCH(DMI_BOARD_NAME, "JFL92") }, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_BIOS_VENDOR, "Micro-Star")}, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star")}, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-Star")}, NULL},
 	{
-	ec_flag_msi, "MSI hardware", {
+	ec_use_busy_polling, "MSI hardware", {
 	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-STAR")}, NULL},
 	{
-	ec_flag_msi, "Quanta hardware", {
+	ec_use_busy_polling, "Quanta hardware", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
 	DMI_MATCH(DMI_PRODUCT_NAME, "TW8/SW8/DW8"),}, NULL},
 	{
-	ec_flag_msi, "Quanta hardware", {
+	ec_use_busy_polling, "Quanta hardware", {
 	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
 	DMI_MATCH(DMI_PRODUCT_NAME, "TW9/SW9"),}, NULL},
 	{
-	ec_flag_msi, "Clevo W350etq", {
+	ec_use_busy_polling, "Clevo W350etq", {
 	DMI_MATCH(DMI_SYS_VENDOR, "CLEVO CO."),
 	DMI_MATCH(DMI_PRODUCT_NAME, "W35_37ET"),}, NULL},
 	{
-- 
1.7.10

[PATCH v2 6/6] ACPI / EC: Remove non-root-caused busy polling quirks.

[Lv Zheng]

We have fixed a lot of race issues in the EC driver recently.

The following commit introduces MSI udelay()/msleep() quirk to MSI laptops
to make EC firmware working for bug 12011 without root causing any EC
driver race issues:
  Commit: 5423a0cb3f74c16e90683f8ee1cec6c240a9556e
  Subject: ACPI: EC: Add delay for slow MSI controller
  Commit: 34ff4dbccccce54c83b1234d39b7ad9e548a75dd
  Subject: ACPI: EC: Separate delays for MSI hardware

The following commit extends ECDT validation quirk to MSI laptops to make
EC driver locating EC registers properly for bug 12461:
  Commit: a5032bfdd9c80e0231a6324661e123818eb46ecd
  Subject: ACPI: EC: Always parse EC device
This is a different quirk than the MSI udelay()/msleep() quirk. This patch
keeps validating ECDT for only "Micro-Star MS-171F" as reported.

The following commit extends MSI udelay()/msleep() quirk to Quanta laptops
to make EC firmware working for bug 20242, there is no requirement to
validate ECDT for Quanta laptops:
  Commit: 534bc4e3d27096e2f3fc00c14a20efd597837a4f Mon Sep 17 00:00:00 2001
  Subject: ACPI EC: enable MSI workaround for Quanta laptops

The following commit extends MSI udelay()/msleep() quirk to Clevo laptops
to make EC firmware working for bug 77431, there is no requirement to
validate ECDT for Clevo laptops:
  Commit: 777cb382958851c88763253fe00a26529be4c0e9
  Subject: ACPI / EC: Add msi quirk for Clevo W350etq

All udelay()/msleep() quirks for MSI/Quanta/Clevo seem to be the wrong
fixes generated without fixing the EC driver race issues.
And even if it is not wrong, the guarding can be covered by the following
commits in wait polling mode:
  Commit: 9e295ac14d6a59180beed0735e6a504c2ee87761
  Subject: ACPI / EC: Reduce ec_poll() by referencing the last register access timestamp.
  Commit: right before this commit
  Subject: ACPI / EC: Merge register access guarding logics.
The only case that is not covered is the inter-transaction guarding. And
there is no evidence that we need the inter-transaction guarding upon
reading the noted bug entries.

So it is time to remove the quirks and let the users to try again. If there
is a regression, the only thing we need to do is to restore the
inter-transaction guarding for the reported platforms.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=12011
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=12461
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=20242
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=77431
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   35 +++--------------------------------
 1 file changed, 3 insertions(+), 32 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 846e0617..149b5e7 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1269,15 +1269,6 @@ static int ec_validate_ecdt(const struct dmi_system_id *id)
 	return 0;
 }
 
-/* EC firmware needs special polling mode, enable it */
-static int ec_use_busy_polling(const struct dmi_system_id *id)
-{
-	pr_debug("Detected the EC firmware requiring busy polling mode.\n");
-	ec_busy_polling = 1;
-	EC_FLAGS_VALIDATE_ECDT = 1;
-	return 0;
-}
-
 /*
  * Acer EC firmware refuses to respond QR_EC when SCI_EVT is not set, for
  * which case, we complete the QR_EC without issuing it to the firmware.
@@ -1320,29 +1311,9 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
 	DMI_MATCH(DMI_BIOS_VENDOR, "COMPAL"),
 	DMI_MATCH(DMI_BOARD_NAME, "JFL92") }, NULL},
 	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_BIOS_VENDOR, "Micro-Star")}, NULL},
-	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star")}, NULL},
-	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-Star")}, NULL},
-	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-STAR")}, NULL},
-	{
-	ec_use_busy_polling, "Quanta hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
-	DMI_MATCH(DMI_PRODUCT_NAME, "TW8/SW8/DW8"),}, NULL},
-	{
-	ec_use_busy_polling, "Quanta hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
-	DMI_MATCH(DMI_PRODUCT_NAME, "TW9/SW9"),}, NULL},
-	{
-	ec_use_busy_polling, "Clevo W350etq", {
-	DMI_MATCH(DMI_SYS_VENDOR, "CLEVO CO."),
-	DMI_MATCH(DMI_PRODUCT_NAME, "W35_37ET"),}, NULL},
+	ec_validate_ecdt, "MSI MS-171F", {
+	DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star"),
+	DMI_MATCH(DMI_PRODUCT_NAME, "MS-171F"),}, NULL},
 	{
 	ec_validate_ecdt, "ASUS hardware", {
 	DMI_MATCH(DMI_BIOS_VENDOR, "ASUS") }, NULL},
-- 
1.7.10

[PATCH v2 6/6] ACPI / EC: Remove non-root-caused busy polling quirks.

[Lv Zheng]

We have fixed a lot of race issues in the EC driver recently.

The following commit introduces MSI udelay()/msleep() quirk to MSI laptops
to make EC firmware working for bug 12011 without root causing any EC
driver race issues:
  Commit: 5423a0cb3f74c16e90683f8ee1cec6c240a9556e
  Subject: ACPI: EC: Add delay for slow MSI controller
  Commit: 34ff4dbccccce54c83b1234d39b7ad9e548a75dd
  Subject: ACPI: EC: Separate delays for MSI hardware

The following commit extends ECDT validation quirk to MSI laptops to make
EC driver locating EC registers properly for bug 12461:
  Commit: a5032bfdd9c80e0231a6324661e123818eb46ecd
  Subject: ACPI: EC: Always parse EC device
This is a different quirk than the MSI udelay()/msleep() quirk. This patch
keeps validating ECDT for only "Micro-Star MS-171F" as reported.

The following commit extends MSI udelay()/msleep() quirk to Quanta laptops
to make EC firmware working for bug 20242, there is no requirement to
validate ECDT for Quanta laptops:
  Commit: 534bc4e3d27096e2f3fc00c14a20efd597837a4f Mon Sep 17 00:00:00 2001
  Subject: ACPI EC: enable MSI workaround for Quanta laptops

The following commit extends MSI udelay()/msleep() quirk to Clevo laptops
to make EC firmware working for bug 77431, there is no requirement to
validate ECDT for Clevo laptops:
  Commit: 777cb382958851c88763253fe00a26529be4c0e9
  Subject: ACPI / EC: Add msi quirk for Clevo W350etq

All udelay()/msleep() quirks for MSI/Quanta/Clevo seem to be the wrong
fixes generated without fixing the EC driver race issues.
And even if it is not wrong, the guarding can be covered by the following
commits in wait polling mode:
  Commit: 9e295ac14d6a59180beed0735e6a504c2ee87761
  Subject: ACPI / EC: Reduce ec_poll() by referencing the last register access timestamp.
  Commit: right before this commit
  Subject: ACPI / EC: Merge register access guarding logics.
The only case that is not covered is the inter-transaction guarding. And
there is no evidence that we need the inter-transaction guarding upon
reading the noted bug entries.

So it is time to remove the quirks and let the users to try again. If there
is a regression, the only thing we need to do is to restore the
inter-transaction guarding for the reported platforms.

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=12011
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=12461
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=20242
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=77431
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
---
 drivers/acpi/ec.c |   35 +++--------------------------------
 1 file changed, 3 insertions(+), 32 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 846e0617..149b5e7 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1269,15 +1269,6 @@ static int ec_validate_ecdt(const struct dmi_system_id *id)
 	return 0;
 }
 
-/* EC firmware needs special polling mode, enable it */
-static int ec_use_busy_polling(const struct dmi_system_id *id)
-{
-	pr_debug("Detected the EC firmware requiring busy polling mode.\n");
-	ec_busy_polling = 1;
-	EC_FLAGS_VALIDATE_ECDT = 1;
-	return 0;
-}
-
 /*
  * Acer EC firmware refuses to respond QR_EC when SCI_EVT is not set, for
  * which case, we complete the QR_EC without issuing it to the firmware.
@@ -1320,29 +1311,9 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
 	DMI_MATCH(DMI_BIOS_VENDOR, "COMPAL"),
 	DMI_MATCH(DMI_BOARD_NAME, "JFL92") }, NULL},
 	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_BIOS_VENDOR, "Micro-Star")}, NULL},
-	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star")}, NULL},
-	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-Star")}, NULL},
-	{
-	ec_use_busy_polling, "MSI hardware", {
-	DMI_MATCH(DMI_CHASSIS_VENDOR, "MICRO-STAR")}, NULL},
-	{
-	ec_use_busy_polling, "Quanta hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
-	DMI_MATCH(DMI_PRODUCT_NAME, "TW8/SW8/DW8"),}, NULL},
-	{
-	ec_use_busy_polling, "Quanta hardware", {
-	DMI_MATCH(DMI_SYS_VENDOR, "Quanta"),
-	DMI_MATCH(DMI_PRODUCT_NAME, "TW9/SW9"),}, NULL},
-	{
-	ec_use_busy_polling, "Clevo W350etq", {
-	DMI_MATCH(DMI_SYS_VENDOR, "CLEVO CO."),
-	DMI_MATCH(DMI_PRODUCT_NAME, "W35_37ET"),}, NULL},
+	ec_validate_ecdt, "MSI MS-171F", {
+	DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star"),
+	DMI_MATCH(DMI_PRODUCT_NAME, "MS-171F"),}, NULL},
 	{
 	ec_validate_ecdt, "ASUS hardware", {
 	DMI_MATCH(DMI_BIOS_VENDOR, "ASUS") }, NULL},
-- 
1.7.10

Re: [PATCH v2 0/6] ACPI / EC: Update due to recent changes.

[Rafael J. Wysocki]

On Friday, May 15, 2015 02:16:05 PM Lv Zheng wrote:
> This patchset tries to cleanup the EC driver to reflect the recent changes.
> There is a small fix in the patchset to use time_before() instead of
> time_after().
> The last patch removes all non-root-caused MSI quirks so that we may be
> able to identify their root cause if regressions are reported against this
> removal and generate new quirks based on the new code base.
> 
> Lv Zheng (6):
>   ACPI / EC: Update acpi_ec_is_gpe_raised() with new GPE status flag.
>   ACPI / EC: Remove storming threashold enlarging quirk.
>   ACPI / EC: Remove irqs_disabled() check.
>   ACPI / EC: Fix and clean up register access guarding logics.
>   ACPI / EC: Add module params for polling modes.
>   ACPI / EC: Remove non-root-caused busy polling quirks.
> 
>  drivers/acpi/ec.c       |  148 ++++++++++++++++++++++-------------------------
>  drivers/acpi/internal.h |    1 +
>  2 files changed, 69 insertions(+), 80 deletions(-)

All of these make sense to me, so I'm queuing them up for 4.2, thanks!


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.