On Saturday, March 01, 2014 12:42:28 AM Kieran Clancy wrote:
> A number of Samsung notebooks (530Uxx/535Uxx/540Uxx/550Pxx/900Xxx/etc)
> continue to log events during sleep (lid open/close, AC plug/unplug,
> battery level change), which accumulate in the EC until a buffer fills.
> After the buffer is full (tests suggest it holds 8 events), GPEs stop
> being triggered for new events. This state persists on wake or even on
> power cycle, and prevents new events from being registered until the EC
> is manually polled.
>
> This is the root cause of a number of bugs, including AC not being
> detected properly, lid close not triggering suspend, and low ambient
> light not triggering the keyboard backlight. The bug also seemed to be
> responsible for performance issues on at least one user's machine.
>
> Juan Manuel Cabo found the cause of bug and the workaround of polling
> the EC manually on wake.
>
> The loop which clears the stale events is based on an earlier patch by
> Lan Tianyu (see referenced attachment).
>
> This patch:
> - Adds a function acpi_ec_clear() which polls the EC for stale _Q
> events at most ACPI_EC_CLEAR_MAX (currently 100) times. A warning is
> logged if this limit is reached.
> - Adds a flag EC_FLAGS_CLEAR_ON_RESUME which is set to 1 if the DMI
> system vendor is Samsung. This check could be replaced by several
> more specific DMI vendor/product pairs, but it's likely that the bug
> affects more Samsung products than just the five series mentioned
> above. Further, it should not be harmful to run acpi_ec_clear() on
> systems without the bug; it will return immediately after finding no
> data waiting.
> - Runs acpi_ec_clear() on initialisation (boot), from acpi_ec_add()
> - Runs acpi_ec_clear() on wake, from acpi_ec_unblock_transactions()
>
> References: https://bugzilla.kernel.org/show_bug.cgi?id=44161
> References: https://bugzilla.kernel.org/show_bug.cgi?id=45461
> References: https://bugzilla.kernel.org/show_bug.cgi?id=57271
> References: https://bugzilla.kernel.org/attachment.cgi?id=126801
> Signed-off-by: Kieran Clancy <clancy.kie...@gmail.com>
> Suggested-by: Juan Manuel Cabo <juanmanuel.c...@gmail.com>
> Reviewed-by: Lan Tianyu <tianyu....@intel.com>
> Reviewed-by: Dennis Jansen <dennis.jan...@web.de>
> Tested-by: Kieran Clancy <clancy.kie...@gmail.com>
> Tested-by: Juan Manuel Cabo <juanmanuel.c...@gmail.com>
> Tested-by: Dennis Jansen <dennis.jan...@web.de>
> Tested-by: Maurizio D'Addona <mauritiusd...@gmail.com>
> Tested-by: San Zamoyski <s...@plusnet.pl>
Queued up for 3.15, thanks!
> ---
>
> Changes in PATCH v2:
> - Changed some of the 'Signed-off-by' lines to better reflect contributions,
> as suggested by Rafael J. Wysocki <r...@rjwysocki.net>.
> - Directly reference prior work by Lan Tianyu.
> - Increase ACPI_EC_CLEAR_MAX to 100, after discussion with
> Li Guang <lig.f...@cn.fujitsu.com> and Juan Manuel Cabo.
> - Made source comments more explicit, thanks to suggestions by Li Guang.
> - Marked warning for hitting ACPI_EC_CLEAR_MAX as unlikely(), as suggested by
> Dennis Jansen.
>
> drivers/acpi/ec.c | 64
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index 959d41a..d7d32c2 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -67,6 +67,8 @@ 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_CLEAR_MAX 100 /* Maximum number of events to query
> + * when trying to clear the EC */
>
> enum {
> EC_FLAGS_QUERY_PENDING, /* Query is pending */
> @@ -116,6 +118,7 @@ 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
> */
>
> /* --------------------------------------------------------------------------
> Transaction Management
> @@ -440,6 +443,29 @@ acpi_handle ec_get_handle(void)
>
> EXPORT_SYMBOL(ec_get_handle);
>
> +static int acpi_ec_query_unlocked(struct acpi_ec *ec, u8 *data);
> +
> +/*
> + * Clears stale _Q events that might have accumulated in the EC.
> + * Run with locked ec mutex.
> + */
> +static void acpi_ec_clear(struct acpi_ec *ec)
> +{
> + int i, status;
> + u8 value = 0;
> +
> + for (i = 0; i < ACPI_EC_CLEAR_MAX; i++) {
> + status = acpi_ec_query_unlocked(ec, &value);
> + if (status || !value)
> + break;
> + }
> +
> + if (unlikely(i == ACPI_EC_CLEAR_MAX))
> + pr_warn("Warning: Maximum of %d stale EC events cleared\n", i);
> + else
> + pr_info("%d stale EC events cleared\n", i);
> +}
> +
> void acpi_ec_block_transactions(void)
> {
> struct acpi_ec *ec = first_ec;
> @@ -463,6 +489,10 @@ void acpi_ec_unblock_transactions(void)
> mutex_lock(&ec->mutex);
> /* Allow transactions to be carried out again */
> clear_bit(EC_FLAGS_BLOCKED, &ec->flags);
> +
> + if (EC_FLAGS_CLEAR_ON_RESUME)
> + acpi_ec_clear(ec);
> +
> mutex_unlock(&ec->mutex);
> }
>
> @@ -821,6 +851,13 @@ static int acpi_ec_add(struct acpi_device *device)
>
> /* EC is fully operational, allow queries */
> clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
> +
> + /* Clear stale _Q events if hardware might require that */
> + if (EC_FLAGS_CLEAR_ON_RESUME) {
> + mutex_lock(&ec->mutex);
> + acpi_ec_clear(ec);
> + mutex_unlock(&ec->mutex);
> + }
> return ret;
> }
>
> @@ -922,6 +959,30 @@ static int ec_enlarge_storm_threshold(const struct
> dmi_system_id *id)
> return 0;
> }
>
> +/*
> + * On some hardware it is necessary to clear events accumulated by the EC
> during
> + * sleep. These ECs stop reporting GPEs until they are manually polled, if
> too
> + * many events are accumulated. (e.g. Samsung Series 5/9 notebooks)
> + *
> + * https://bugzilla.kernel.org/show_bug.cgi?id=44161
> + *
> + * Ideally, the EC should also be instructed NOT to accumulate events during
> + * sleep (which Windows seems to do somehow), but the interface to control
> this
> + * behaviour is not known at this time.
> + *
> + * Models known to be affected are Samsung
> 530Uxx/535Uxx/540Uxx/550Pxx/900Xxx,
> + * however it is very likely that other Samsung models are affected.
> + *
> + * On systems which don't accumulate _Q events during sleep, this extra check
> + * should be harmless.
> + */
> +static int ec_clear_on_resume(const struct dmi_system_id *id)
> +{
> + pr_debug("Detected system needing EC poll on resume.\n");
> + EC_FLAGS_CLEAR_ON_RESUME = 1;
> + return 0;
> +}
> +
> static struct dmi_system_id ec_dmi_table[] __initdata = {
> {
> ec_skip_dsdt_scan, "Compal JFL92", {
> @@ -965,6 +1026,9 @@ static struct dmi_system_id ec_dmi_table[] __initdata = {
> ec_validate_ecdt, "ASUS hardware", {
> DMI_MATCH(DMI_SYS_VENDOR, "ASUSTek Computer Inc."),
> DMI_MATCH(DMI_PRODUCT_NAME, "L4R"),}, NULL},
> + {
> + ec_clear_on_resume, "Samsung hardware", {
> + DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD.")}, NULL},
> {},
> };
>
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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