ACPI: EC: do transaction from interrupt context

It is easier and faster to do transaction directly from interrupt context
rather than waking control thread.
Also, cleaner GPE storm avoidance is implemented.
References: 	http://bugzilla.kernel.org/show_bug.cgi?id=9998
		http://bugzilla.kernel.org/show_bug.cgi?id=10724
		http://bugzilla.kernel.org/show_bug.cgi?id=10919
		http://bugzilla.kernel.org/show_bug.cgi?id=11309
		http://bugzilla.kernel.org/show_bug.cgi?id=11549
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 149 insertions, 160 deletions

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 13593f9f2197..7f0d81c0ec99 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1,7 +1,7 @@
 /*
- *  ec.c - ACPI Embedded Controller Driver (v2.0)
+ *  ec.c - ACPI Embedded Controller Driver (v2.1)
  *
- *  Copyright (C) 2006, 2007 Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
+ *  Copyright (C) 2006-2008 Alexey Starikovskiy <astarikovskiy@suse.de>
  *  Copyright (C) 2006 Denis Sadykov <denis.m.sadykov@intel.com>
  *  Copyright (C) 2004 Luming Yu <luming.yu@intel.com>
  *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
@@ -26,7 +26,7 @@
  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  */
 
-/* Uncomment next line to get verbose print outs*/
+/* Uncomment next line to get verbose printout */
 /* #define DEBUG */
 
 #include <linux/kernel.h>
@@ -38,6 +38,7 @@
 #include <linux/seq_file.h>
 #include <linux/interrupt.h>
 #include <linux/list.h>
+#include <linux/spinlock.h>
 #include <asm/io.h>
 #include <acpi/acpi_bus.h>
 #include <acpi/acpi_drivers.h>
@@ -65,22 +66,21 @@ enum ec_command {
         ACPI_EC_COMMAND_QUERY = 0x84,
 };
 
-/* EC events */
-enum ec_event {
-        ACPI_EC_EVENT_OBF_1 = 1,        /* Output buffer full */
-        ACPI_EC_EVENT_IBF_0,            /* Input buffer empty */
-};
-
 #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_UDELAY          100     /* Wait 100us before polling EC again */
 
+#define ACPI_EC_STORM_THRESHOLD 20      /* number of false interrupts
+                                           per one transaction */
+
 enum {
-        EC_FLAGS_WAIT_GPE = 0,          /* Don't check status until GPE arrives */
         EC_FLAGS_QUERY_PENDING,         /* Query is pending */
-        EC_FLAGS_GPE_MODE,              /* Expect GPE to be sent for status change */
+        EC_FLAGS_GPE_MODE,              /* Expect GPE to be sent
+                                         * for status change */
         EC_FLAGS_NO_GPE,                /* Don't use GPE mode */
-        EC_FLAGS_RESCHEDULE_POLL        /* Re-schedule poll */
+        EC_FLAGS_GPE_STORM,             /* GPE storm detected */
+        EC_FLAGS_HANDLERS_INSTALLED     /* Handlers for GPE and
+                                         * OpReg are installed */
 };
 
 /* If we find an EC via the ECDT, we need to keep a ptr to its context */
@@ -95,6 +95,14 @@ struct acpi_ec_query_handler {
         u8 query_bit;
 };
 
+struct transaction_data {
+        const u8 *wdata;
+        u8 *rdata;
+        unsigned short irq_count;
+        u8 wlen;
+        u8 rlen;
+};
+
 static struct acpi_ec {
         acpi_handle handle;
         unsigned long gpe;
@@ -105,9 +113,8 @@ static struct acpi_ec {
         struct mutex lock;
         wait_queue_head_t wait;
         struct list_head list;
-        struct delayed_work work;
-        atomic_t irq_count;
-        u8 handlers_installed;
+        struct transaction_data *t;
+        spinlock_t t_lock;
 } *boot_ec, *first_ec;
 
 /* 
@@ -150,7 +157,7 @@ static inline u8 acpi_ec_read_data(struct acpi_ec *ec)
 {
         u8 x = inb(ec->data_addr);
         pr_debug(PREFIX "---> data = 0x%2.2x\n", x);
-        return inb(ec->data_addr);
+        return x;
 }
 
 static inline void acpi_ec_write_cmd(struct acpi_ec *ec, u8 command)
@@ -165,68 +172,79 @@ static inline void acpi_ec_write_data(struct acpi_ec *ec, u8 data)
         outb(data, ec->data_addr);
 }
 
-static inline int acpi_ec_check_status(struct acpi_ec *ec, enum ec_event event)
+static int ec_transaction_done(struct acpi_ec *ec)
 {
-        if (test_bit(EC_FLAGS_WAIT_GPE, &ec->flags))
-                return 0;
-        if (event == ACPI_EC_EVENT_OBF_1) {
-                if (acpi_ec_read_status(ec) & ACPI_EC_FLAG_OBF)
-                        return 1;
-        } else if (event == ACPI_EC_EVENT_IBF_0) {
-                if (!(acpi_ec_read_status(ec) & ACPI_EC_FLAG_IBF))
-                        return 1;
-        }
-
-        return 0;
+        unsigned long flags;
+        int ret = 0;
+        spin_lock_irqsave(&ec->t_lock, flags);
+        if (!ec->t || (!ec->t->wlen && !ec->t->rlen))
+                ret = 1;
+        spin_unlock_irqrestore(&ec->t_lock, flags);
+        return ret;
 }
 
-static void ec_schedule_ec_poll(struct acpi_ec *ec)
+static void gpe_transaction(struct acpi_ec *ec, u8 status)
 {
-        if (test_bit(EC_FLAGS_RESCHEDULE_POLL, &ec->flags))
-                schedule_delayed_work(&ec->work,
-                                      msecs_to_jiffies(ACPI_EC_DELAY));
+        unsigned long flags;
+        spin_lock_irqsave(&ec->t_lock, flags);
+        if (!ec->t)
+                goto unlock;
+        if (ec->t->wlen > 0) {
+                if ((status & ACPI_EC_FLAG_IBF) == 0) {
+                        acpi_ec_write_data(ec, *(ec->t->wdata++));
+                        --ec->t->wlen;
+                } else
+                        /* false interrupt, state didn't change */
+                        ++ec->t->irq_count;
+
+        } else if (ec->t->rlen > 0) {
+                if ((status & ACPI_EC_FLAG_OBF) == 1) {
+                        *(ec->t->rdata++) = acpi_ec_read_data(ec);
+                        --ec->t->rlen;
+                } else
+                        /* false interrupt, state didn't change */
+                        ++ec->t->irq_count;
+        }
+unlock:
+        spin_unlock_irqrestore(&ec->t_lock, flags);
 }
 
-static void ec_switch_to_poll_mode(struct acpi_ec *ec)
+static int acpi_ec_wait(struct acpi_ec *ec)
 {
+        if (wait_event_timeout(ec->wait, ec_transaction_done(ec),
+                               msecs_to_jiffies(ACPI_EC_DELAY)))
+                return 0;
+        /* missing GPEs, switch back to poll mode */
+        if (printk_ratelimit())
+                pr_info(PREFIX "missing confirmations, "
+                                "switch off interrupt mode.\n");
         set_bit(EC_FLAGS_NO_GPE, &ec->flags);
         clear_bit(EC_FLAGS_GPE_MODE, &ec->flags);
-        acpi_disable_gpe(NULL, ec->gpe, ACPI_NOT_ISR);
-        set_bit(EC_FLAGS_RESCHEDULE_POLL, &ec->flags);
+        return 1;
 }
 
-static int acpi_ec_wait(struct acpi_ec *ec, enum ec_event event, int force_poll)
+static void acpi_ec_gpe_query(void *ec_cxt);
+
+static int ec_check_sci(struct acpi_ec *ec, u8 state)
 {
-        atomic_set(&ec->irq_count, 0);
-        if (likely(test_bit(EC_FLAGS_GPE_MODE, &ec->flags)) &&
-            likely(!force_poll)) {
-                if (wait_event_timeout(ec->wait, acpi_ec_check_status(ec, event),
-                                       msecs_to_jiffies(ACPI_EC_DELAY)))
-                        return 0;
-                clear_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
-                if (acpi_ec_check_status(ec, event)) {
-                        /* missing GPEs, switch back to poll mode */
-                        if (printk_ratelimit())
-                                pr_info(PREFIX "missing confirmations, "
-                                                "switch off interrupt mode.\n");
-                        ec_switch_to_poll_mode(ec);
-                        ec_schedule_ec_poll(ec);
-                        return 0;
-                }
-        } else {
-                unsigned long delay = jiffies + msecs_to_jiffies(ACPI_EC_DELAY);
-                clear_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
-                while (time_before(jiffies, delay)) {
-                        if (acpi_ec_check_status(ec, event))
-                                return 0;
-                        msleep(1);
-                }
-                if (acpi_ec_check_status(ec,event))
+        if (state & ACPI_EC_FLAG_SCI) {
+                if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
+                        return acpi_os_execute(OSL_EC_BURST_HANDLER,
+                                acpi_ec_gpe_query, ec);
+        }
+        return 0;
+}
+
+static int ec_poll(struct acpi_ec *ec)
+{
+        unsigned long delay = jiffies + msecs_to_jiffies(ACPI_EC_DELAY);
+        msleep(1);
+        while (time_before(jiffies, delay)) {
+                gpe_transaction(ec, acpi_ec_read_status(ec));
+                msleep(1);
+                if (ec_transaction_done(ec))
                         return 0;
         }
-        pr_err(PREFIX "acpi_ec_wait timeout, status = 0x%2.2x, event = %s\n",
-                acpi_ec_read_status(ec),
-                (event == ACPI_EC_EVENT_OBF_1) ? "\"b0=1\"" : "\"b1=0\"");
         return -ETIME;
 }
 
@@ -235,45 +253,51 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec, u8 command,
                                         u8 * rdata, unsigned rdata_len,
                                         int force_poll)
 {
-        int result = 0;
-        set_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
+        unsigned long tmp;
+        struct transaction_data t = {.wdata = wdata, .rdata = rdata,
+                                     .wlen = wdata_len, .rlen = rdata_len,
+                                     .irq_count = 0};
+        int ret = 0;
         pr_debug(PREFIX "transaction start\n");
-        acpi_ec_write_cmd(ec, command);
-        for (; wdata_len > 0; --wdata_len) {
-                result = acpi_ec_wait(ec, ACPI_EC_EVENT_IBF_0, force_poll);
-                if (result) {
-                        pr_err(PREFIX
-                               "write_cmd timeout, command = %d\n", command);
-                        goto end;
-                }
-                set_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
-                acpi_ec_write_data(ec, *(wdata++));
+        /* disable GPE during transaction if storm is detected */
+        if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
+                clear_bit(EC_FLAGS_GPE_MODE, &ec->flags);
+                acpi_disable_gpe(NULL, ec->gpe, ACPI_NOT_ISR);
         }
-
-        if (!rdata_len) {
-                result = acpi_ec_wait(ec, ACPI_EC_EVENT_IBF_0, force_poll);
-                if (result) {
-                        pr_err(PREFIX
-                               "finish-write timeout, command = %d\n", command);
-                        goto end;
-                }
-        } else if (command == ACPI_EC_COMMAND_QUERY)
+        /* start transaction */
+        spin_lock_irqsave(&ec->t_lock, tmp);
+        /* following two actions should be kept atomic */
+        ec->t = &t;
+        acpi_ec_write_cmd(ec, command);
+        if (command == ACPI_EC_COMMAND_QUERY)
                 clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
-
-        for (; rdata_len > 0; --rdata_len) {
-                result = acpi_ec_wait(ec, ACPI_EC_EVENT_OBF_1, force_poll);
-                if (result) {
-                        pr_err(PREFIX "read timeout, command = %d\n", command);
-                        goto end;
-                }
-                /* Don't expect GPE after last read */
-                if (rdata_len > 1)
-                        set_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
-                *(rdata++) = acpi_ec_read_data(ec);
-        }
-      end:
+        spin_unlock_irqrestore(&ec->t_lock, tmp);
+        /* if we selected poll mode or failed in GPE-mode do a poll loop */
+        if (force_poll ||
+            !test_bit(EC_FLAGS_GPE_MODE, &ec->flags) ||
+            acpi_ec_wait(ec))
+                ret = ec_poll(ec);
         pr_debug(PREFIX "transaction end\n");
-        return result;
+        spin_lock_irqsave(&ec->t_lock, tmp);
+        ec->t = NULL;
+        spin_unlock_irqrestore(&ec->t_lock, tmp);
+        if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
+                /* check if we received SCI during transaction */
+                ec_check_sci(ec, acpi_ec_read_status(ec));
+                /* it is safe to enable GPE outside of transaction */
+                acpi_enable_gpe(NULL, ec->gpe, ACPI_NOT_ISR);
+        } else if (test_bit(EC_FLAGS_GPE_MODE, &ec->flags) &&
+                   t.irq_count > ACPI_EC_STORM_THRESHOLD) {
+                pr_debug(PREFIX "GPE storm detected\n");
+                set_bit(EC_FLAGS_GPE_STORM, &ec->flags);
+        }
+        return ret;
+}
+
+static int ec_check_ibf0(struct acpi_ec *ec)
+{
+        u8 status = acpi_ec_read_status(ec);
+        return (status & ACPI_EC_FLAG_IBF) == 0;
 }
 
 static int acpi_ec_transaction(struct acpi_ec *ec, u8 command,
@@ -283,40 +307,34 @@ static int acpi_ec_transaction(struct acpi_ec *ec, u8 command,
 {
         int status;
         u32 glk;
-
         if (!ec || (wdata_len && !wdata) || (rdata_len && !rdata))
                 return -EINVAL;
-
         if (rdata)
                 memset(rdata, 0, rdata_len);
-
         mutex_lock(&ec->lock);
         if (ec->global_lock) {
                 status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
                 if (ACPI_FAILURE(status)) {
-                        mutex_unlock(&ec->lock);
-                        return -ENODEV;
+                        status = -ENODEV;
+                        goto unlock;
                 }
         }
-
-        status = acpi_ec_wait(ec, ACPI_EC_EVENT_IBF_0, 0);
-        if (status) {
+        if (!wait_event_timeout(ec->wait, ec_check_ibf0(ec),
+                                msecs_to_jiffies(ACPI_EC_DELAY))) {
                 pr_err(PREFIX "input buffer is not empty, "
                                 "aborting transaction\n");
+                status = -ETIME;
                 goto end;
         }
-
         status = acpi_ec_transaction_unlocked(ec, command,
                                               wdata, wdata_len,
                                               rdata, rdata_len,
                                               force_poll);
-
-      end:
-
+end:
         if (ec->global_lock)
                 acpi_release_global_lock(glk);
+unlock:
         mutex_unlock(&ec->lock);
-
         return status;
 }
 
@@ -332,7 +350,9 @@ int acpi_ec_burst_enable(struct acpi_ec *ec)
 
 int acpi_ec_burst_disable(struct acpi_ec *ec)
 {
-        return acpi_ec_transaction(ec, ACPI_EC_BURST_DISABLE, NULL, 0, NULL, 0, 0);
+        return (acpi_ec_read_status(ec) & ACPI_EC_FLAG_BURST) ?
+                acpi_ec_transaction(ec, ACPI_EC_BURST_DISABLE,
+                        NULL, 0, NULL, 0, 0) : 0;
 }
 
 static int acpi_ec_read(struct acpi_ec *ec, u8 address, u8 * data)
@@ -513,46 +533,26 @@ static void acpi_ec_gpe_query(void *ec_cxt)
 
 static u32 acpi_ec_gpe_handler(void *data)
 {
-        acpi_status status = AE_OK;
         struct acpi_ec *ec = data;
-        u8 state = acpi_ec_read_status(ec);
+        u8 status;
 
         pr_debug(PREFIX "~~~> interrupt\n");
-        atomic_inc(&ec->irq_count);
-        if (atomic_read(&ec->irq_count) > 5) {
-                pr_err(PREFIX "GPE storm detected, disabling EC GPE\n");
-                ec_switch_to_poll_mode(ec);
-                goto end;
-        }
-        clear_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
-        if (test_bit(EC_FLAGS_GPE_MODE, &ec->flags))
+        status = acpi_ec_read_status(ec);
+
+        gpe_transaction(ec, status);
+        if (ec_transaction_done(ec) && (status & ACPI_EC_FLAG_IBF) == 0)
                 wake_up(&ec->wait);
 
-        if (state & ACPI_EC_FLAG_SCI) {
-                if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
-                        status = acpi_os_execute(OSL_EC_BURST_HANDLER,
-                                acpi_ec_gpe_query, ec);
-        } else if (!test_bit(EC_FLAGS_GPE_MODE, &ec->flags) &&
-                   !test_bit(EC_FLAGS_NO_GPE, &ec->flags) &&
-                   in_interrupt()) {
+        ec_check_sci(ec, status);
+        if (!test_bit(EC_FLAGS_GPE_MODE, &ec->flags) &&
+            !test_bit(EC_FLAGS_NO_GPE, &ec->flags)) {
                 /* this is non-query, must be confirmation */
                 if (printk_ratelimit())
                         pr_info(PREFIX "non-query interrupt received,"
                                 " switching to interrupt mode\n");
                 set_bit(EC_FLAGS_GPE_MODE, &ec->flags);
-                clear_bit(EC_FLAGS_RESCHEDULE_POLL, &ec->flags);
         }
-end:
-        ec_schedule_ec_poll(ec);
-        return ACPI_SUCCESS(status) ?
-            ACPI_INTERRUPT_HANDLED : ACPI_INTERRUPT_NOT_HANDLED;
-}
-
-static void do_ec_poll(struct work_struct *work)
-{
-        struct acpi_ec *ec = container_of(work, struct acpi_ec, work.work);
-        atomic_set(&ec->irq_count, 0);
-        (void)acpi_ec_gpe_handler(ec);
+        return ACPI_INTERRUPT_HANDLED;
 }
 
 /* --------------------------------------------------------------------------
@@ -696,8 +696,7 @@ static struct acpi_ec *make_acpi_ec(void)
         mutex_init(&ec->lock);
         init_waitqueue_head(&ec->wait);
         INIT_LIST_HEAD(&ec->list);
-        INIT_DELAYED_WORK_DEFERRABLE(&ec->work, do_ec_poll);
-        atomic_set(&ec->irq_count, 0);
+        spin_lock_init(&ec->t_lock);
         return ec;
 }
 
@@ -736,22 +735,15 @@ ec_parse_device(acpi_handle handle, u32 Level, void *context, void **retval)
         return AE_CTRL_TERMINATE;
 }
 
-static void ec_poll_stop(struct acpi_ec *ec)
-{
-        clear_bit(EC_FLAGS_RESCHEDULE_POLL, &ec->flags);
-        cancel_delayed_work(&ec->work);
-}
-
 static void ec_remove_handlers(struct acpi_ec *ec)
 {
-        ec_poll_stop(ec);
         if (ACPI_FAILURE(acpi_remove_address_space_handler(ec->handle,
                                 ACPI_ADR_SPACE_EC, &acpi_ec_space_handler)))
                 pr_err(PREFIX "failed to remove space handler\n");
         if (ACPI_FAILURE(acpi_remove_gpe_handler(NULL, ec->gpe,
                                 &acpi_ec_gpe_handler)))
                 pr_err(PREFIX "failed to remove gpe handler\n");
-        ec->handlers_installed = 0;
+        clear_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags);
 }
 
 static int acpi_ec_add(struct acpi_device *device)
@@ -846,17 +838,15 @@ ec_parse_io_ports(struct acpi_resource *resource, void *context)
 static int ec_install_handlers(struct acpi_ec *ec)
 {
         acpi_status status;
-        if (ec->handlers_installed)
+        if (test_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags))
                 return 0;
         status = acpi_install_gpe_handler(NULL, ec->gpe,
-                                          ACPI_GPE_EDGE_TRIGGERED,
-                                          &acpi_ec_gpe_handler, ec);
+                                  ACPI_GPE_EDGE_TRIGGERED,
+                                  &acpi_ec_gpe_handler, ec);
         if (ACPI_FAILURE(status))
                 return -ENODEV;
-
         acpi_set_gpe_type(NULL, ec->gpe, ACPI_GPE_TYPE_RUNTIME);
         acpi_enable_gpe(NULL, ec->gpe, ACPI_NOT_ISR);
-
         status = acpi_install_address_space_handler(ec->handle,
                                                     ACPI_ADR_SPACE_EC,
                                                     &acpi_ec_space_handler,
@@ -866,7 +856,7 @@ static int ec_install_handlers(struct acpi_ec *ec)
                 return -ENODEV;
         }
 
-        ec->handlers_installed = 1;
+        set_bit(EC_FLAGS_HANDLERS_INSTALLED, &ec->flags);
         return 0;
 }
 
@@ -887,7 +877,6 @@ static int acpi_ec_start(struct acpi_device *device)
 
         /* EC is fully operational, allow queries */
         clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
-        ec_schedule_ec_poll(ec);
         return ret;
 }
 
@@ -906,7 +895,7 @@ static int acpi_ec_stop(struct acpi_device *device, int type)
 
 int __init acpi_boot_ec_enable(void)
 {
-        if (!boot_ec || boot_ec->handlers_installed)
+        if (!boot_ec || test_bit(EC_FLAGS_HANDLERS_INSTALLED, &boot_ec->flags))
                 return 0;
         if (!ec_install_handlers(boot_ec)) {
                 first_ec = boot_ec;