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ACPI / EC: Introduce STARTED/STOPPED flags to replace BLOCKED flag
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By using the 2 flags, we can indicate an inter-mediate state where the
current transactions should be completed while the new transactions should
be dropped.

The comparison of the old flag and the new flags:
  Old			New
  about to set BLOCKED	STOPPED set / STARTED set
  BLOCKED set		STOPPED clear / STARTED clear
  BLOCKED clear		STOPPED clear / STARTED set
A new period can be indicated by the 2 flags. The new period is between the
point where we are about to set BLOCKED and the point when the BLOCKED is
set. The new flags facilitate us with acpi_ec_started() check to allow the
EC transaction to be submitted during the new period. This period thus can
be used as a grace period for the EC transaction flushing.

The only functional change after applying this patch is:
1. The GPE enabling/disabling is protected by the EC specific lock. We can
   do this because of recent ACPICA GPE API enhancement. This is reasonable
   as the GPE disabling/enabling state should only be determined by the EC
   driver's state machine which is protected by the EC spinlock.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Tested-by: Ortwin Glück <odi@odi.ch>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Lv Zheng authored and Rafael J. Wysocki committed Feb 6, 2015
1 parent a8d4fc2 commit ad479e7
Showing 1 changed file with 54 additions and 11 deletions.
65 changes: 54 additions & 11 deletions drivers/acpi/ec.c
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,8 @@ enum {
EC_FLAGS_GPE_STORM, /* GPE storm detected */
EC_FLAGS_HANDLERS_INSTALLED, /* Handlers for GPE and
* OpReg are installed */
EC_FLAGS_BLOCKED, /* Transactions are blocked */
EC_FLAGS_STARTED, /* Driver is started */
EC_FLAGS_STOPPED, /* Driver is stopped */
};

#define ACPI_EC_COMMAND_POLL 0x01 /* Available for command byte */
Expand Down Expand Up @@ -134,6 +135,16 @@ 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 */
static int EC_FLAGS_QUERY_HANDSHAKE; /* Needs QR_EC issued when SCI_EVT set */

/* --------------------------------------------------------------------------
* Device Flags
* -------------------------------------------------------------------------- */

static bool acpi_ec_started(struct acpi_ec *ec)
{
return test_bit(EC_FLAGS_STARTED, &ec->flags) &&
!test_bit(EC_FLAGS_STOPPED, &ec->flags);
}

/* --------------------------------------------------------------------------
* EC Registers
* -------------------------------------------------------------------------- */
Expand Down Expand Up @@ -415,6 +426,10 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
udelay(ACPI_EC_MSI_UDELAY);
/* start transaction */
spin_lock_irqsave(&ec->lock, tmp);
if (!acpi_ec_started(ec)) {
ret = -EINVAL;
goto unlock;
}
/* following two actions should be kept atomic */
ec->curr = t;
pr_debug("***** Command(%s) started *****\n",
Expand All @@ -426,6 +441,7 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
pr_debug("***** Command(%s) stopped *****\n",
acpi_ec_cmd_string(t->command));
ec->curr = NULL;
unlock:
spin_unlock_irqrestore(&ec->lock, tmp);
return ret;
}
Expand All @@ -440,10 +456,6 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
if (t->rdata)
memset(t->rdata, 0, t->rlen);
mutex_lock(&ec->mutex);
if (test_bit(EC_FLAGS_BLOCKED, &ec->flags)) {
status = -EINVAL;
goto unlock;
}
if (ec->global_lock) {
status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
if (ACPI_FAILURE(status)) {
Expand Down Expand Up @@ -595,6 +607,37 @@ static void acpi_ec_clear(struct acpi_ec *ec)
pr_info("%d stale EC events cleared\n", i);
}

static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
{
unsigned long flags;

spin_lock_irqsave(&ec->lock, flags);
if (!test_and_set_bit(EC_FLAGS_STARTED, &ec->flags)) {
pr_debug("+++++ Starting EC +++++\n");
if (!resuming)
acpi_ec_enable_gpe(ec, true);
pr_info("+++++ EC started +++++\n");
}
spin_unlock_irqrestore(&ec->lock, flags);
}

static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
{
unsigned long flags;

spin_lock_irqsave(&ec->lock, flags);
if (acpi_ec_started(ec)) {
pr_debug("+++++ Stopping EC +++++\n");
set_bit(EC_FLAGS_STOPPED, &ec->flags);
if (!suspending)
acpi_ec_disable_gpe(ec, true);
clear_bit(EC_FLAGS_STARTED, &ec->flags);
clear_bit(EC_FLAGS_STOPPED, &ec->flags);
pr_info("+++++ EC stopped +++++\n");
}
spin_unlock_irqrestore(&ec->lock, flags);
}

void acpi_ec_block_transactions(void)
{
struct acpi_ec *ec = first_ec;
Expand All @@ -604,7 +647,7 @@ void acpi_ec_block_transactions(void)

mutex_lock(&ec->mutex);
/* Prevent transactions from being carried out */
set_bit(EC_FLAGS_BLOCKED, &ec->flags);
acpi_ec_stop(ec, true);
mutex_unlock(&ec->mutex);
}

Expand All @@ -616,7 +659,7 @@ void acpi_ec_unblock_transactions(void)
return;

/* Allow transactions to be carried out again */
clear_bit(EC_FLAGS_BLOCKED, &ec->flags);
acpi_ec_start(ec, true);

if (EC_FLAGS_CLEAR_ON_RESUME)
acpi_ec_clear(ec);
Expand All @@ -629,7 +672,7 @@ void acpi_ec_unblock_transactions_early(void)
* atomic context during wakeup, so we don't need to acquire the mutex).
*/
if (first_ec)
clear_bit(EC_FLAGS_BLOCKED, &first_ec->flags);
acpi_ec_start(first_ec, true);
}

/* --------------------------------------------------------------------------
Expand Down Expand Up @@ -894,7 +937,7 @@ static int ec_install_handlers(struct acpi_ec *ec)
if (ACPI_FAILURE(status))
return -ENODEV;

acpi_ec_enable_gpe(ec, true);
acpi_ec_start(ec, false);
status = acpi_install_address_space_handler(ec->handle,
ACPI_ADR_SPACE_EC,
&acpi_ec_space_handler,
Expand All @@ -909,7 +952,7 @@ static int ec_install_handlers(struct acpi_ec *ec)
pr_err("Fail in evaluating the _REG object"
" of EC device. Broken bios is suspected.\n");
} else {
acpi_ec_disable_gpe(ec, true);
acpi_ec_stop(ec, false);
acpi_remove_gpe_handler(NULL, ec->gpe,
&acpi_ec_gpe_handler);
return -ENODEV;
Expand All @@ -924,7 +967,7 @@ static void ec_remove_handlers(struct acpi_ec *ec)
{
if (!test_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags))
return;
acpi_ec_disable_gpe(ec, true);
acpi_ec_stop(ec, false);
if (ACPI_FAILURE(acpi_remove_address_space_handler(ec->handle,
ACPI_ADR_SPACE_EC, &acpi_ec_space_handler)))
pr_err("failed to remove space handler\n");
Expand Down

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