V4L/DVB (9595): cx18: Improve handling of outgoing mailboxes detected to be busy

cx18: Improve handling of outgoing mailboxes detected to be busy.  When
encountering a busy mailbox, sleep instead of polling, and wait for interrupt or
timeout.  If the mailbox is still busy, force it free.  When sending commands,
make sure we never create a situation where we mark the mailbox busy upon
sending, and ensure we always have a method to cleanly recover from a busy
mailbox.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 64 insertions, 69 deletions

diff --git a/drivers/media/video/cx18/cx18-irq.c b/drivers/media/video/cx18/cx18-irq.c
index 37b931055d3a..4912b3c8e6a5 100644
--- a/drivers/media/video/cx18/cx18-irq.c
+++ b/drivers/media/video/cx18/cx18-irq.c
@@ -167,7 +167,8 @@ irqreturn_t cx18_irq_handler(int irq, void *dev_id)
                 cx18_write_reg_expect(cx, hw2, HW2_INT_CLR_STATUS, ~hw2, hw2);
 
         if (sw1 || sw2 || hw2)
-                CX18_DEBUG_HI_IRQ("SW1: %x  SW2: %x  HW2: %x\n", sw1, sw2, hw2);
+                CX18_DEBUG_HI_IRQ("received interrupts "
+                                  "SW1: %x  SW2: %x  HW2: %x\n", sw1, sw2, hw2);
 
         /* To do: interrupt-based I2C handling
         if (hw2 & (HW2_I2C1_INT|HW2_I2C2_INT)) {
diff --git a/drivers/media/video/cx18/cx18-mailbox.c b/drivers/media/video/cx18/cx18-mailbox.c
index d2975a2e6cb7..0de4b9a7bbca 100644
--- a/drivers/media/video/cx18/cx18-mailbox.c
+++ b/drivers/media/video/cx18/cx18-mailbox.c
@@ -92,48 +92,6 @@ static const struct cx18_api_info *find_api_info(u32 cmd)
         return NULL;
 }
 
-static struct cx18_mailbox __iomem *cx18_mb_is_complete(struct cx18 *cx, int rpu,
-                u32 *state, u32 *irq, u32 *req)
-{
-        struct cx18_mailbox __iomem *mb = NULL;
-        int wait_count = 0;
-        u32 ack;
-
-        switch (rpu) {
-        case APU:
-                mb = &cx->scb->epu2apu_mb;
-                *state = cx18_readl(cx, &cx->scb->apu_state);
-                *irq = cx18_readl(cx, &cx->scb->epu2apu_irq);
-                break;
-
-        case CPU:
-                mb = &cx->scb->epu2cpu_mb;
-                *state = cx18_readl(cx, &cx->scb->cpu_state);
-                *irq = cx18_readl(cx, &cx->scb->epu2cpu_irq);
-                break;
-
-        default:
-                break;
-        }
-
-        if (mb == NULL)
-                return mb;
-
-        do {
-                *req = cx18_readl(cx, &mb->request);
-                ack = cx18_readl(cx, &mb->ack);
-                wait_count++;
-        } while (*req != ack && wait_count < 600);
-
-        if (*req == ack) {
-                (*req)++;
-                if (*req == 0 || *req == 0xffffffff)
-                        *req = 1;
-                return mb;
-        }
-        return NULL;
-}
-
 long cx18_mb_ack(struct cx18 *cx, const struct cx18_mailbox *mb, int rpu)
 {
         struct cx18_mailbox __iomem *ack_mb;
@@ -164,12 +122,13 @@ long cx18_mb_ack(struct cx18 *cx, const struct cx18_mailbox *mb, int rpu)
 static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 {
         const struct cx18_api_info *info = find_api_info(cmd);
-        u32 state = 0, irq = 0, req, oldreq, err;
+        u32 state, irq, req, ack, err;
         struct cx18_mailbox __iomem *mb;
+        u32 __iomem *xpu_state;
         wait_queue_head_t *waitq;
         struct mutex *mb_lock;
         int timeout = 100;
-        int sig = 0;
+        long unsigned int j, ret;
         int i;
 
         if (info == NULL) {
@@ -186,10 +145,16 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
         case APU:
                 waitq = &cx->mb_apu_waitq;
                 mb_lock = &cx->epu2apu_mb_lock;
+                irq = IRQ_EPU_TO_APU;
+                mb = &cx->scb->epu2apu_mb;
+                xpu_state = &cx->scb->apu_state;
                 break;
         case CPU:
                 waitq = &cx->mb_cpu_waitq;
                 mb_lock = &cx->epu2cpu_mb_lock;
+                irq = IRQ_EPU_TO_CPU;
+                mb = &cx->scb->epu2cpu_mb;
+                xpu_state = &cx->scb->cpu_state;
                 break;
         default:
                 CX18_WARN("Unknown RPU (%d) for API call\n", info->rpu);
@@ -198,51 +163,85 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 
         mutex_lock(mb_lock);
         cx18_setup_page(cx, SCB_OFFSET);
-        mb = cx18_mb_is_complete(cx, info->rpu, &state, &irq, &req);
 
-        if (mb == NULL) {
-                mutex_unlock(mb_lock);
-                CX18_ERR("mb %s busy\n", info->name);
-                return -EBUSY;
-        }
+        /*
+         * Wait for an in-use mailbox to complete
+         *
+         * If the XPU is responding with Ack's, the mailbox shouldn't be in
+         * a busy state, since we serialize access to it on our end.
+         *
+         * If the wait for ack after sending a previous command was interrupted
+         * by a signal, we may get here and find a busy mailbox.  After waiting,
+         * mark it "not busy" from our end, if the XPU hasn't ack'ed it still.
+         */
+        state = cx18_readl(cx, xpu_state);
+        req = cx18_readl(cx, &mb->request);
+        j = msecs_to_jiffies(timeout);
+        ret = wait_event_timeout(*waitq,
+                                 (ack = cx18_readl(cx, &mb->ack)) == req,
+                                 j);
+        if (req != ack) {
+                /* waited long enough, make the mbox "not busy" from our end */
+                cx18_writel(cx, req, &mb->ack);
+                CX18_ERR("mbox was found stuck busy when setting up for %s; "
+                         "clearing busy and trying to proceed\n", info->name);
+        } else if (ret != j)
+                CX18_DEBUG_API("waited %u usecs for busy mbox to be acked\n",
+                               jiffies_to_usecs(j-ret));
+
+        /* Build the outgoing mailbox */
+        req = ((req & 0xfffffffe) == 0xfffffffe) ? 1 : req + 1;
 
-        oldreq = req - 1;
         cx18_writel(cx, cmd, &mb->cmd);
         for (i = 0; i < args; i++)
                 cx18_writel(cx, data[i], &mb->args[i]);
         cx18_writel(cx, 0, &mb->error);
         cx18_writel(cx, req, &mb->request);
+        cx18_writel(cx, req - 1, &mb->ack); /* ensure ack & req are distinct */
 
+        /* Notify the XPU and wait for it to send an Ack back */
         if (info->flags & API_FAST)
                 timeout /= 2;
+        j = msecs_to_jiffies(timeout);
+
+        CX18_DEBUG_HI_IRQ("sending interrupt SW1: %x to send %s\n",
+                          irq, info->name);
         cx18_write_reg_expect(cx, irq, SW1_INT_SET, irq, irq);
 
-        sig = wait_event_interruptible_timeout(
+        ret = wait_event_interruptible_timeout(
                        *waitq,
                        cx18_readl(cx, &mb->ack) == cx18_readl(cx, &mb->request),
-                       msecs_to_jiffies(timeout));
-        if (sig == 0) {
+                       j);
+        if (ret == 0) {
                 /* Timed out */
-                cx18_writel(cx, oldreq, &mb->request);
                 mutex_unlock(mb_lock);
-                CX18_ERR("sending %s timed out waiting for RPU to respond\n",
-                         info->name);
+                CX18_ERR("sending %s timed out waiting for RPU "
+                         "acknowledgement\n", info->name);
                 return -EINVAL;
-        } else if (sig < 0) {
+        } else if (ret < 0) {
                 /* Interrupted */
-                cx18_writel(cx, oldreq, &mb->request);
                 mutex_unlock(mb_lock);
-                CX18_WARN("sending %s interrupted waiting for RPU to respond\n",
-                          info->name);
+                CX18_WARN("sending %s was interrupted waiting for RPU"
+                          "acknowledgement\n", info->name);
                 return -EINTR;
-        }
+        } else if (ret != j)
+                CX18_DEBUG_HI_API("waited %u usecs for %s to be acked\n",
+                                  jiffies_to_usecs(j-ret), info->name);
 
+        /* Collect data returned by the XPU */
         for (i = 0; i < MAX_MB_ARGUMENTS; i++)
                 data[i] = cx18_readl(cx, &mb->args[i]);
         err = cx18_readl(cx, &mb->error);
         mutex_unlock(mb_lock);
+
+        /*
+         * Wait for XPU to perform extra actions for the caller in some cases.
+         * e.g. CX18_CPU_DE_RELEASE_MDL will cause the CPU to send all buffers
+         * back in a burst shortly thereafter
+         */
         if (info->flags & API_SLOW)
                 cx18_msleep_timeout(300, 0);
+
         if (err)
                 CX18_DEBUG_API("mailbox error %08x for command %s\n", err,
                                 info->name);
@@ -251,12 +250,7 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 
 int cx18_api(struct cx18 *cx, u32 cmd, int args, u32 data[])
 {
-        int res = cx18_api_call(cx, cmd, args, data);
-
-        /* Allow a single retry, probably already too late though.
-           If there is no free mailbox then that is usually an indication
-           of a more serious problem. */
-        return (res == -EBUSY) ? cx18_api_call(cx, cmd, args, data) : res;
+        return cx18_api_call(cx, cmd, args, data);
 }
 
 static int cx18_set_filter_param(struct cx18_stream *s)