radeon: Sane handling of timeouts in WaitForVerticalSync(2).

RADEONWaitForVerticalSync() and RADEONWaitForVerticalSync2() need to wait
for a timeout specified in milliseconds; looping around usleep() causes
the timeout to be unnecessarily long, as the OS may sleep longer than
requested (on Linux the minimum actual sleep value may be several ms).

The new logic uses gettimeofday() in the loop to see when the (absolute)
timeout has arrived.

Signed-off-by: Alon Ziv <alonz@nolaviz.org>

2 files changed, 31 insertions, 10 deletions

diff --git a/src/radeon.h b/src/radeon.h
index b19b017e..9e70ab58 100644
--- a/src/radeon.h
+++ b/src/radeon.h
@@ -39,6 +39,8 @@
 
 #include <stdlib.h>		/* For abs() */
 #include <unistd.h>		/* For usleep() */
+#include <sys/time.h>		/* For
+#include <time.h>		 * gettimeofday() */
 
 #include "xf86str.h"
 #include "compiler.h"
@@ -189,6 +191,8 @@ typedef struct _region {
 #define RADEON_IDLE_RETRY      16 /* Fall out of idle loops after this count */
 #define RADEON_TIMEOUT    2000000 /* Fall out of wait loops after this count */
 
+#define RADEON_VSYNC_TIMEOUT	20000 /* Maximum wait for VSYNC (in usecs) */
+
 /* Buffer are aligned on 4096 byte boundaries */
 #define RADEON_BUFFER_ALIGN 0x00000fff
 #define RADEON_VBIOS_SIZE 0x00010000
@@ -1175,4 +1179,21 @@ static __inline__ void RADEON_SYNC(RADEONInfoPtr info, ScrnInfoPtr pScrn)
 #endif
 }
 
+static __inline__ void radeon_init_timeout(struct timeval *endtime,
+    unsigned int timeout)
+{
+    gettimeofday(endtime, NULL);
+    endtime->tv_usec += timeout;
+    endtime->tv_sec += endtime->tv_usec / 1000000;
+    endtime->tv_usec %= 1000000;
+}
+
+static __inline__ int radeon_timedout(const struct timeval *endtime)
+{
+    struct timeval now;
+    gettimeofday(&now, NULL);
+    return now.tv_sec == endtime->tv_sec ?
+        now.tv_usec > endtime->tv_usec : now.tv_sec > endtime->tv_sec;
+}
+
 #endif /* _RADEON_H_ */
diff --git a/src/radeon_driver.c b/src/radeon_driver.c
index 894131fa..418b39d1 100644
--- a/src/radeon_driver.c
+++ b/src/radeon_driver.c
@@ -759,7 +759,7 @@ void RADEONWaitForVerticalSync(ScrnInfoPtr pScrn)
     RADEONInfoPtr  info       = RADEONPTR(pScrn);
     unsigned char *RADEONMMIO = info->MMIO;
     CARD32         crtc_gen_cntl;
-    int            i;
+    struct timeval timeout;
 
     crtc_gen_cntl = INREG(RADEON_CRTC_GEN_CNTL);
     if ((crtc_gen_cntl & RADEON_CRTC_DISP_REQ_EN_B) ||
@@ -770,10 +770,10 @@ void RADEONWaitForVerticalSync(ScrnInfoPtr pScrn)
     OUTREG(RADEON_CRTC_STATUS, RADEON_CRTC_VBLANK_SAVE_CLEAR);
 
     /* Wait for it to go back up */
-    for (i = 0; i < RADEON_TIMEOUT/1000; i++) {
-	if (INREG(RADEON_CRTC_STATUS) & RADEON_CRTC_VBLANK_SAVE) break;
-	usleep(1);
-    }
+    radeon_init_timeout(&timeout, RADEON_VSYNC_TIMEOUT);
+    while (!(INREG(RADEON_CRTC_STATUS) & RADEON_CRTC_VBLANK_SAVE) &&
+        !radeon_timedout(&timeout))
+	usleep(100);
 }
 
 /* Wait for vertical sync on secondary CRTC */
@@ -782,7 +782,7 @@ void RADEONWaitForVerticalSync2(ScrnInfoPtr pScrn)
     RADEONInfoPtr  info       = RADEONPTR(pScrn);
     unsigned char *RADEONMMIO = info->MMIO;
     CARD32         crtc2_gen_cntl;
-    int            i;
+    struct timeval timeout;
  
     crtc2_gen_cntl = INREG(RADEON_CRTC2_GEN_CNTL);
     if ((crtc2_gen_cntl & RADEON_CRTC2_DISP_REQ_EN_B) ||
@@ -793,10 +793,10 @@ void RADEONWaitForVerticalSync2(ScrnInfoPtr pScrn)
     OUTREG(RADEON_CRTC2_STATUS, RADEON_CRTC2_VBLANK_SAVE_CLEAR);
 
     /* Wait for it to go back up */
-    for (i = 0; i < RADEON_TIMEOUT/1000; i++) {
-	if (INREG(RADEON_CRTC2_STATUS) & RADEON_CRTC2_VBLANK_SAVE) break;
-	usleep(1);
-    }
+    radeon_init_timeout(&timeout, RADEON_VSYNC_TIMEOUT);
+    while (!(INREG(RADEON_CRTC2_STATUS) & RADEON_CRTC2_VBLANK_SAVE) &&
+        !radeon_timedout(&timeout))
+	usleep(100);
 }