Re: [PATCH] ACPI / EC: Clear stale EC events on Samsung systems

[Li Guang <lig.fnst@cn.fujitsu.com>]

Juan Manuel Cabo wrote:
>
>    
>> that's really nasty EC firmware!
>>      
> Yes!
> And this bug has been unsolved for about two years.
>
>    
>> 20 is enough?
>> the query index is length of a byte.
>>
>>      
> According to our humble tests, 8 is the maximum number of
> accumulated events. For instance, if the one plugs or unplugs the PSU
> 16 times, (or battery % changes 16 times) during S3 sleep, then the
> EC returns no more than 8 events when polled by this patch or by
> my userspace util.
> And having reached 8 events, it won't produce its GPE until queried.
>    

that surely indicts their EC firmware only queued 8 events,

>    
>> the query index is length of a byte.
>>      
> There is no query index, unless you refer to something else (I'm sorry if its
> something that escapes me).
>    

oh, sorry, I'm referring internal EC firmware code
for Q event queuing, not ACPI SPEC, ;-)
for machine you tested, 8 is the queue size,
but for some unknown also nasty EC firmwares(let's suppose it exists),
it may queue more Q events.
and I saw several firmwares queued 32 events by default,
then, let's say, they be used for some samsung products,
and also they also forgot to deal with sleep/resume state,
then, we'll also leave stale Q event there.

Thanks!

>      For us, a query is just: send 0x84 through EC CMD port, and read status
> from CMD port and event type from EC DATA port. This is done with
> the usual ec.c functions that would handle a query after a GPE interrupt,
> but using them instead to poll (not GPE initiated) at awake. The EC would
> then return status without 0x20 mask and 'event type'==0 when no more left.
>
> --
> Juan Manuel Cabo<juanmanuel.cabo@gmail.com>
>
>
>
>    
>>>    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; /* EC should be polled on boot/resume */
>>>
>>>        
>> seems name is implicit, what about EC_FLAGS_QEVENT_CLR_ON_RESUME?
>> seems too long :-)
>>
>>      
>>>    /* --------------------------------------------------------------------------
>>>                                 Transaction Management
>>> @@ -440,6 +443,26 @@ acpi_handle ec_get_handle(void)
>>>
>>>    EXPORT_SYMBOL(ec_get_handle);
>>>
>>> +static int acpi_ec_query_unlocked(struct acpi_ec *ec, u8 *data);
>>> +
>>> +/* 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 (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 +486,10 @@ 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 +848,13 @@ static int acpi_ec_add(struct acpi_device *device)
>>>
>>>        /* EC is fully operational, allow queries */
>>>        clear_bit(EC_FLAGS_QUERY_PENDING,&ec->flags);
>>> +
>>> +    /* Some hardware may need the EC to be cleared before use */
>>>
>>>        
>> description is implicit, should specify what we clear is Q event, not EC.
>>
>> Thanks!
>> Li Guang
>>
>>      
>>> +    if (EC_FLAGS_CLEAR_ON_RESUME) {
>>> +        mutex_lock(&ec->mutex);
>>> +        acpi_ec_clear(ec);
>>> +        mutex_unlock(&ec->mutex);
>>> +    }
>>>        return ret;
>>>    }
>>>
>>> @@ -922,6 +956,30 @@ 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 EC 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 +1023,9 @@ 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},
>>>        {},
>>>    };
>>>
>>>
>>>        
>>
>>      
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>
>