V4L/DVB (9110): cx18: Add default behavior of checking and retrying PCI MMIO accesses

cx18: Add default behavior of checking and retrying PCI MMIO accesses.
The concept of checking and retrying PCI MMIO accesses for better reliability
in older motherboards was suggested by Steve Toth <stoth@linuxtv.org>.  This
change implements MMIO retries and the retry_mmio module parameter that is
enabled by default.  Limited experiments have shown this is more reliable than
the mmio_ndelay parameter.  mmio_ndelay has insignificant effect with retries
enabled.

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

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/media/video/cx18/cx18-driver.h b/drivers/media/video/cx18/cx18-driver.h
index 66cb748875c7..80f5f563d4fc 100644
--- a/drivers/media/video/cx18/cx18-driver.h
+++ b/drivers/media/video/cx18/cx18-driver.h
@@ -171,6 +171,7 @@
 
 #define CX18_MAX_PGM_INDEX (400)
 
+extern int cx18_retry_mmio;     /* enable check & retry of mmio accesses */
 extern int cx18_debug;
 
 
@@ -344,6 +345,13 @@ struct cx18_i2c_algo_callback_data {
         int bus_index;   /* 0 or 1 for the cx23418's 1st or 2nd I2C bus */
 };
 
+#define CX18_MAX_MMIO_RETRIES 10
+
+struct cx18_mmio_stats {
+        atomic_t retried_write[CX18_MAX_MMIO_RETRIES+1];
+        atomic_t retried_read[CX18_MAX_MMIO_RETRIES+1];
+};
+
 /* Struct to hold info about cx18 cards */
 struct cx18 {
         int num;                /* board number, -1 during init! */
@@ -433,6 +441,9 @@ struct cx18 {
         u32 gpio_val;
         struct mutex gpio_lock;
 
+        /* Statistics */
+        struct cx18_mmio_stats mmio_stats;
+
         /* v4l2 and User settings */
 
         /* codec settings */