mmc: tmio_mmc: handle missing HW interrupts

When doing excessive hotplug, e.g., repeated insert/eject operations,
the hardware may get confused to a point where no CMDTIMEOUT/CMDRESPEND
interrupts are generated any more.  As a result requests get stuck, e.g.:

[  360.351562] INFO: task kworker/u:0:5 blocked for more than 120 seconds.
[  360.351562] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  360.359375] kworker/u:0   D c020c2b4     0     5      2 0x00000000
[  360.367187] Backtrace:
[  360.367187] [<c020bfb0>] (schedule+0x0/0x340) from [<c020c480>] (schedule_timeout+0x20/0x190)
[  360.375000]  r8:c702fd70 r7:00000002 r6:c702e000 r5:c702fdc4 r4:7fffffff
[  360.375000] r3:c701e040
[  360.382812] [<c020c460>] (schedule_timeout+0x0/0x190) from [<c020be78>] (wait_for_common+0xc4/0x150)
[  360.390625]  r6:c702e000 r5:c702fdc4 r4:7fffffff
[  360.390625] [<c020bdb4>] (wait_for_common+0x0/0x150) from [<c020bfac>] (wait_for_completion+0x18/0x1c)
[  360.398437] [<c020bf94>] (wait_for_completion+0x0/0x1c) from [<c0185590>] (mmc_wait_for_req+0x214/0x234)
[  360.406250] [<c018537c>] (mmc_wait_for_req+0x0/0x234) from [<c01889d0>] (mmc_sd_switch+0xfc/0x114)
[  360.414062]  r7:c702fe4c r6:c702fe20 r5:c7179800 r4:00fffff0
[  360.421875] [<c01888d4>] (mmc_sd_switch+0x0/0x114) from [<c0187f70>] (mmc_sd_setup_card+0x260/0x384)
[  360.429687] [<c0187d10>] (mmc_sd_setup_card+0x0/0x384) from [<c01885e0>] (mmc_sd_init_card+0x13c/0x1e0)
[  360.437500] [<c01884a4>] (mmc_sd_init_card+0x0/0x1e0) from [<c01887a8>] (mmc_attach_sd+0x124/0x1a8)
[  360.445312]  r8:c02db404 r7:ffffff92 r6:c702ff34 r5:c6007da8 r4:c6007c00
[  360.453125] [<c0188684>] (mmc_attach_sd+0x0/0x1a8) from [<c0185140>] (mmc_rescan+0x248/0x2f0)
[  360.460937]  r5:c6007da8 r4:c6007c00
[  360.468750] [<c0184ef8>] (mmc_rescan+0x0/0x2f0) from [<c00467f0>] (process_one_work+0x1ec/0x318)
[  360.476562]  r7:c6007da8 r6:00000000 r5:c710ec00 r4:c701bde0
[  360.484375] [<c0046604>] (process_one_work+0x0/0x318) from [<c0047fb0>] (worker_thread+0x1b0/0x2cc)
[  360.492187] [<c0047e00>] (worker_thread+0x0/0x2cc) from [<c004b338>] (kthread+0x8c/0x94)
[  360.500000] [<c004b2ac>] (kthread+0x0/0x94) from [<c0037fc4>] (do_exit+0x0/0x590)
[  360.507812]  r7:00000013 r6:c0037fc4 r5:c004b2ac r4:c7021f00

This patch addresses this problem by introducing timeouts for outstanding
interrupts. If a hardware interrupt is missing, a soft reset will be
performed to bring the hardware back to a working state.
Tested with the SDHI hardware block in sh7372 / AP4EVB.

Signed-off-by: Arnd Hannemann <arnd@arndnet.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 86 insertions, 4 deletions

diff --git a/drivers/mmc/host/tmio_mmc.c b/drivers/mmc/host/tmio_mmc.c
index 81bed310ddcd..689a3692242e 100644
--- a/drivers/mmc/host/tmio_mmc.c
+++ b/drivers/mmc/host/tmio_mmc.c
@@ -39,6 +39,8 @@
 #include <linux/module.h>
 #include <linux/pagemap.h>
 #include <linux/scatterlist.h>
+#include <linux/workqueue.h>
+#include <linux/spinlock.h>
 
 #define CTL_SD_CMD 0x00
 #define CTL_ARG_REG 0x04
@@ -154,6 +156,11 @@ struct tmio_mmc_host {
         u8                      bounce_buf[PAGE_CACHE_SIZE] __attribute__((aligned(MAX_ALIGN)));
         struct scatterlist      bounce_sg;
 #endif
+
+        /* Track lost interrupts */
+        struct delayed_work     delayed_reset_work;
+        spinlock_t              lock;
+        unsigned long           last_req_ts;
 };
 
 static void tmio_check_bounce_buffer(struct tmio_mmc_host *host);
@@ -345,15 +352,60 @@ static void reset(struct tmio_mmc_host *host)
         msleep(10);
 }
 
+static void tmio_mmc_reset_work(struct work_struct *work)
+{
+        struct tmio_mmc_host *host = container_of(work, struct tmio_mmc_host,
+                                                  delayed_reset_work.work);
+        struct mmc_request *mrq;
+        unsigned long flags;
+
+        spin_lock_irqsave(&host->lock, flags);
+        mrq = host->mrq;
+
+        /* request already finished */
+        if (!mrq
+            || time_is_after_jiffies(host->last_req_ts +
+                msecs_to_jiffies(2000))) {
+                spin_unlock_irqrestore(&host->lock, flags);
+                return;
+        }
+
+        dev_warn(&host->pdev->dev,
+                "timeout waiting for hardware interrupt (CMD%u)\n",
+                mrq->cmd->opcode);
+
+        if (host->data)
+                host->data->error = -ETIMEDOUT;
+        else if (host->cmd)
+                host->cmd->error = -ETIMEDOUT;
+        else
+                mrq->cmd->error = -ETIMEDOUT;
+
+        host->cmd = NULL;
+        host->data = NULL;
+        host->mrq = NULL;
+
+        spin_unlock_irqrestore(&host->lock, flags);
+
+        reset(host);
+
+        mmc_request_done(host->mmc, mrq);
+}
+
 static void
 tmio_mmc_finish_request(struct tmio_mmc_host *host)
 {
         struct mmc_request *mrq = host->mrq;
 
+        if (!mrq)
+                return;
+
         host->mrq = NULL;
         host->cmd = NULL;
         host->data = NULL;
 
+        cancel_delayed_work(&host->delayed_reset_work);
+
         mmc_request_done(host->mmc, mrq);
 }
 
@@ -463,6 +515,7 @@ static void tmio_mmc_pio_irq(struct tmio_mmc_host *host)
         return;
 }
 
+/* needs to be called with host->lock held */
 static void tmio_mmc_do_data_irq(struct tmio_mmc_host *host)
 {
         struct mmc_data *data = host->data;
@@ -519,10 +572,12 @@ static void tmio_mmc_do_data_irq(struct tmio_mmc_host *host)
 
 static void tmio_mmc_data_irq(struct tmio_mmc_host *host)
 {
-        struct mmc_data *data = host->data;
+        struct mmc_data *data;
+        spin_lock(&host->lock);
+        data = host->data;
 
         if (!data)
-                return;
+                goto out;
 
         if (host->chan_tx && (data->flags & MMC_DATA_WRITE)) {
                 /*
@@ -543,6 +598,8 @@ static void tmio_mmc_data_irq(struct tmio_mmc_host *host)
         } else {
                 tmio_mmc_do_data_irq(host);
         }
+out:
+        spin_unlock(&host->lock);
 }
 
 static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host,
@@ -551,9 +608,11 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host,
         struct mmc_command *cmd = host->cmd;
         int i, addr;
 
+        spin_lock(&host->lock);
+
         if (!host->cmd) {
                 pr_debug("Spurious CMD irq\n");
-                return;
+                goto out;
         }
 
         host->cmd = NULL;
@@ -598,6 +657,9 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host,
                 tmio_mmc_finish_request(host);
         }
 
+out:
+        spin_unlock(&host->lock);
+
         return;
 }
 
@@ -906,6 +968,12 @@ static void tmio_issue_tasklet_fn(unsigned long priv)
 static void tmio_tasklet_fn(unsigned long arg)
 {
         struct tmio_mmc_host *host = (struct tmio_mmc_host *)arg;
+        unsigned long flags;
+
+        spin_lock_irqsave(&host->lock, flags);
+
+        if (!host->data)
+                goto out;
 
         if (host->data->flags & MMC_DATA_READ)
                 dma_unmap_sg(&host->pdev->dev, host->sg_ptr, host->dma_sglen,
@@ -915,6 +983,8 @@ static void tmio_tasklet_fn(unsigned long arg)
                              DMA_TO_DEVICE);
 
         tmio_mmc_do_data_irq(host);
+out:
+        spin_unlock_irqrestore(&host->lock, flags);
 }
 
 /* It might be necessary to make filter MFD specific */
@@ -1037,6 +1107,8 @@ static void tmio_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
         if (host->mrq)
                 pr_debug("request not null\n");
 
+        host->last_req_ts = jiffies;
+        wmb();
         host->mrq = mrq;
 
         if (mrq->data) {
@@ -1046,10 +1118,14 @@ static void tmio_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
         }
 
         ret = tmio_mmc_start_command(host, mrq->cmd);
-        if (!ret)
+        if (!ret) {
+                schedule_delayed_work(&host->delayed_reset_work,
+                                      msecs_to_jiffies(2000));
                 return;
+        }
 
 fail:
+        host->mrq = NULL;
         mrq->cmd->error = ret;
         mmc_request_done(mmc, mrq);
 }
@@ -1247,6 +1323,11 @@ static int __devinit tmio_mmc_probe(struct platform_device *dev)
         if (ret)
                 goto cell_disable;
 
+        spin_lock_init(&host->lock);
+
+        /* Init delayed work for request timeouts */
+        INIT_DELAYED_WORK(&host->delayed_reset_work, tmio_mmc_reset_work);
+
         /* See if we also get DMA */
         tmio_mmc_request_dma(host, pdata);
 
@@ -1285,6 +1366,7 @@ static int __devexit tmio_mmc_remove(struct platform_device *dev)
         if (mmc) {
                 struct tmio_mmc_host *host = mmc_priv(mmc);
                 mmc_remove_host(mmc);
+                cancel_delayed_work_sync(&host->delayed_reset_work);
                 tmio_mmc_release_dma(host);
                 free_irq(host->irq, host);
                 if (cell->disable)