OMAP: DSS2: DSI: use a private workqueue
Using the shared workqueue led to to a deadlock in the case where the
display was unblanked via keyboard.
What happens is something like this:
- User presses a key
context 1:
- drivers/char/keyboard.c calls schedule_console_callback()
- fb_unblank takes the console semaphore
- dsi bus lock is taken, and frame transfer is started (dsi bus lock is
left on)
- Unblank code tries to set the panel backlight, which tries to take dsi
bus lock, but is blocked while the frame transfer is going on
context 2, shared workqueue, console_callback in drivers/char/vt.c:
- Tries to take console semaphore
- Blocks, as console semaphore is being held by context 1
- No other shared workqueue work can be run
context 3, HW irq, caused by FRAMEDONE interrupt:
- Interrupt handler schedules framedone-work in shared workqueue
- Framedone-work is never ran, as the shared workqueue is blocked. This
means that the unblank thread stays blocked, which means that context 2
stays blocked.
While I think the real problem is in keyboard/virtual terminal code, using
a private workqueue in the DSI driver is perhaps safer and more robust
than using the shared one. The DSI works should not be delayed more than a
millisecond or so, and even if the private workqueue gives us no hard
promise of doing so, it's still safer bet than the shared workqueue.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>
diff --git a/drivers/video/omap2/dss/dsi.c b/drivers/video/omap2/dss/dsi.c
index 542c6e2..de3fdab 100644
--- a/drivers/video/omap2/dss/dsi.c
+++ b/drivers/video/omap2/dss/dsi.c
@@ -238,6 +238,8 @@
bool te_enabled;
+ struct workqueue_struct *workqueue;
+
struct work_struct framedone_work;
void (*framedone_callback)(int, void *);
void *framedone_data;
@@ -2759,6 +2761,7 @@
unsigned packet_payload;
unsigned packet_len;
u32 l;
+ int r;
const unsigned channel = dsi.update_channel;
/* line buffer is 1024 x 24bits */
/* XXX: for some reason using full buffer size causes considerable TX
@@ -2809,8 +2812,9 @@
dsi_perf_mark_start();
- schedule_delayed_work(&dsi.framedone_timeout_work,
+ r = queue_delayed_work(dsi.workqueue, &dsi.framedone_timeout_work,
msecs_to_jiffies(250));
+ BUG_ON(r == 0);
dss_start_update(dssdev);
@@ -2841,6 +2845,11 @@
DSSERR("Framedone not received for 250ms!\n");
+ /* XXX While extremely unlikely, we could get FRAMEDONE interrupt after
+ * 250ms which would conflict with this timeout work. What should be
+ * done is first cancel the transfer on the HW, and then cancel the
+ * possibly scheduled framedone work */
+
/* SIDLEMODE back to smart-idle */
dispc_enable_sidle();
@@ -2873,6 +2882,7 @@
static void dsi_framedone_irq_callback(void *data, u32 mask)
{
+ int r;
/* Note: We get FRAMEDONE when DISPC has finished sending pixels and
* turns itself off. However, DSI still has the pixels in its buffers,
* and is sending the data.
@@ -2881,7 +2891,8 @@
/* SIDLEMODE back to smart-idle */
dispc_enable_sidle();
- schedule_work(&dsi.framedone_work);
+ r = queue_work(dsi.workqueue, &dsi.framedone_work);
+ BUG_ON(r == 0);
}
static void dsi_handle_framedone(void)
@@ -3292,6 +3303,10 @@
mutex_init(&dsi.lock);
sema_init(&dsi.bus_lock, 1);
+ dsi.workqueue = create_singlethread_workqueue("dsi");
+ if (dsi.workqueue == NULL)
+ return -ENOMEM;
+
INIT_WORK(&dsi.framedone_work, dsi_framedone_work_callback);
INIT_DELAYED_WORK_DEFERRABLE(&dsi.framedone_timeout_work,
dsi_framedone_timeout_work_callback);
@@ -3328,6 +3343,7 @@
err2:
iounmap(dsi.base);
err1:
+ destroy_workqueue(dsi.workqueue);
return r;
}
@@ -3335,6 +3351,8 @@
{
iounmap(dsi.base);
+ destroy_workqueue(dsi.workqueue);
+
DSSDBG("omap_dsi_exit\n");
}