gridseed: Reduce traffic sending work to GridSeed devices

Only send new work to a device when:
There is new work available
Or there is an error reading from the device
Or enough time has passed to scan a full nonce range

driver-gridseed.c

@@ -19,7 +19,9 @@
 #include "gc3355.h"
 
 #define GRIDSEED_DEFAULT_FREQUENCY  600
-#define GRIDSEED_HASH_SPEED			0.0851128926	// in ms
+
+// 60Kh/s at 700MHz in ms
+#define GRIDSEED_HASH_SPEED			0.08571428571429
 
 BFG_REGISTER_DRIVER(gridseed_drv)
 
@@ -202,23 +204,44 @@ static
 int64_t gridseed_scanhash(struct thr_info *thr, struct work *work, int64_t __maybe_unused max_nonce)
 {
 	struct cgpu_info *device = thr->cgpu;
+	struct gc3355_orb_info *info = device->device_data;
+	struct timeval tv_nonce_range, tv_hashes_done;
+
+	// total hashrate of this device:
+	uint32_t hashes_per_sec = GRIDSEED_HASH_SPEED * (double)(1000 * info->freq * info->chips);
+	// amount of time it takes this device to scan a nonce range:
+	uint32_t nonce_range_sec = 0xffffffff / hashes_per_sec;
+	// timer to break out of scanning should we scan an entire nonce range
+	timer_set_delay_from_now(&tv_nonce_range, nonce_range_sec * 1000000);
+
+	// timer to estimate hashes every 10s for runs of no shares
+	const uint32_t hashes_delay = 10 * 1000000;
+	timer_set_delay_from_now(&tv_hashes_done, hashes_delay);
 
 	unsigned char buf[GC3355_READ_SIZE];
 	int read = 0;
 	int fd = device->device_fd;
 
-	while (!thr->work_restart && (read = gc3355_read(fd, (char *)buf, GC3355_READ_SIZE)) > 0)
+	while (!thr->work_restart &&											// true when new work is available (miner.c)
+		   (read = gc3355_read(fd, (char *)buf, GC3355_READ_SIZE)) >= 0 &&	// only check for failure - allow 0 bytes
+		   !timer_passed(&tv_nonce_range, NULL))							// true when we've had time to scan a range
 	{
-		if ((buf[0] == 0x55) && (buf[1] == 0x20))
+		if (timer_passed(&tv_hashes_done, NULL))
+		{
+			hashes_done2(thr, gridseed_estimate_hashes(thr), NULL);
+			timer_set_delay_from_now(&tv_hashes_done, hashes_delay);
+		}
+
+		if (read == 0)
+			continue;
+		else if ((buf[0] == 0x55) && (buf[1] == 0x20))
 		{
-			// LTC result
 			gridseed_submit_nonce(thr, buf, work);
+			hashes_done2(thr, gridseed_estimate_hashes(thr), NULL);
+			timer_set_delay_from_now(&tv_hashes_done, hashes_delay);
 		}
 		else
-		{
 			applog(LOG_ERR, "%"PRIpreprv": Unrecognized response", device->proc_repr);
-			break;
-		}
 	}
 
 	return gridseed_estimate_hashes(thr);

gc3355.c

@@ -388,22 +388,9 @@ void gc3355_log_protocol(int fd, const char *buf, size_t size, const char *prefi
 	       GC3355_CHIP_NAME, fd, prefix, (unsigned long)size, hex);
 }
 
-int gc3355_read(int fd, char *buf, size_t size)
+ssize_t gc3355_read(int fd, char *buf, size_t size)
 {
-	size_t read;
-	int tries = 20;
-	
-	while (tries > 0)
-	{
-		read = serial_read(fd, buf, size);
-		if (read > 0)
-			break;
-		
-		tries--;
-	}
-	
-	if (unlikely(tries == 0))
-		return -1;
+	size_t read = serial_read(fd, buf, size);
 	
 	if ((read > 0) && opt_dev_protocol)
 		gc3355_log_protocol(fd, buf, read, "RECV");

gc3355.h

@@ -41,7 +41,7 @@ struct gc3355_orb_info
 #define gc3355_open(path)  serial_open(path, 115200, 1, true)
 #define gc3355_close(fd)  serial_close(fd)
 
-extern int gc3355_read(int fd, char *buf, size_t size);
+extern ssize_t gc3355_read(int fd, char *buf, size_t size);
 extern ssize_t gc3355_write(int fd, const void * const buf, const size_t size);
 
 extern void gc3355_init_usborb(int fd, int pll_freq, bool scrypt_only, bool detect_only);