Instead of using complicated sleeps to emulate characters per second on usb writes, submit only as many characters as can be transferred per usb poll of 1ms, and use timeouts in bulk transfers, cancelling transfers only as a failsafe.

usbutils.c

@@ -2412,6 +2412,7 @@ usb_bulk_transfer(struct libusb_device_handle *dev_handle, int intinfo,
 	struct timeval tv_start, tv_finish;
 #endif
 	unsigned char buf[512];
+	int cgto = cgpu->usbdev->found->timeout;
 
 	usb_epinfo = &(cgpu->usbdev->found->intinfos[intinfo].epinfos[epinfo]);
 	endpoint = usb_epinfo->ep;
@@ -2437,12 +2438,12 @@ usb_bulk_transfer(struct libusb_device_handle *dev_handle, int intinfo,
 	init_usb_transfer(&ut);
 	/* We give the transfer no timeout since we manage timeouts ourself */
 	libusb_fill_bulk_transfer(ut.transfer, dev_handle, endpoint, buf, length,
-				  transfer_callback, &ut, 0);
+				  transfer_callback, &ut, timeout);
 	STATS_TIMEVAL(&tv_start);
 	err = usb_submit_transfer(&ut, ut.transfer, cancellable);
 	errn = errno;
 	if (!err)
-		err = callback_wait(&ut, transferred, timeout);
+		err = callback_wait(&ut, transferred, timeout + cgto);
 	complete_usb_transfer(&ut);
 
 	STATS_TIMEVAL(&tv_finish);
@@ -2540,22 +2541,6 @@ int _usb_read(struct cgpu_info *cgpu, int intinfo, int epinfo, char *buf, size_t
 			}
 			got = 0;
 
-			if (first && usbdev->usecps && usbdev->last_write_siz) {
-				cgtimer_t now, already_done;
-				double sleep_estimate;
-				double write_time = (double)(usbdev->last_write_siz) /
-						    (double)(usbdev->cps) * 1000;
-
-				cgtimer_time(&now);
-				cgtimer_sub(&now, &usbdev->cgt_last_write, &already_done);
-				sleep_estimate = write_time - cgtimer_to_ms(&already_done);
-
-				if (sleep_estimate > 0.0) {
-					cgsleep_ms_r(&usbdev->cgt_last_write, write_time);
-					cgpu->usbinfo.read_delay_count++;
-					cgpu->usbinfo.total_read_delay += sleep_estimate;
-				}
-			}
 			err = usb_bulk_transfer(usbdev->handle, intinfo, epinfo,
 						ptr, usbbufread, &got, timeout,
 						cgpu, MODE_BULK_READ, cmd, first ? SEQ0 : SEQ1,
@@ -2641,22 +2626,6 @@ int _usb_read(struct cgpu_info *cgpu, int intinfo, int epinfo, char *buf, size_t
 				usbbufread = bufleft;
 		}
 		got = 0;
-		if (first && usbdev->usecps && usbdev->last_write_siz) {
-			cgtimer_t now, already_done;
-			double sleep_estimate;
-			double write_time = (double)(usbdev->last_write_siz) /
-					    (double)(usbdev->cps) * 1000;
-
-			cgtimer_time(&now);
-			cgtimer_sub(&now, &usbdev->cgt_last_write, &already_done);
-			sleep_estimate = write_time - cgtimer_to_ms(&already_done);
-
-			if (sleep_estimate > 0.0) {
-				cgsleep_ms_r(&usbdev->cgt_last_write, write_time);
-				cgpu->usbinfo.read_delay_count++;
-				cgpu->usbinfo.total_read_delay += sleep_estimate;
-			}
-		}
 		err = usb_bulk_transfer(usbdev->handle, intinfo, epinfo,
 					ptr, usbbufread, &got, timeout,
 					cgpu, MODE_BULK_READ, cmd, first ? SEQ0 : SEQ1,
@@ -2786,29 +2755,15 @@ int _usb_write(struct cgpu_info *cgpu, int intinfo, int epinfo, char *buf, size_
 	max = ((double)timeout) / 1000.0;
 	cgtime(&read_start);
 	while (bufsiz > 0) {
-		sent = 0;
+		int tosend = bufsiz;
+
 		if (usbdev->usecps) {
-			if (usbdev->last_write_siz) {
+			int cpms = usbdev->cps / 1000 ? : 1;
-				cgtimer_t now, already_done;
+			if (tosend > cpms)
-				double sleep_estimate;
+				tosend = cpms;
-				double write_time = (double)(usbdev->last_write_siz) /
-						    (double)(usbdev->cps) * 1000;
-
-				cgtimer_time(&now);
-				cgtimer_sub(&now, &usbdev->cgt_last_write, &already_done);
-				sleep_estimate = write_time - cgtimer_to_ms(&already_done);
-
-				if (sleep_estimate > 0.0) {
-					cgsleep_ms_r(&usbdev->cgt_last_write, write_time);
-					cgpu->usbinfo.write_delay_count++;
-					cgpu->usbinfo.total_write_delay += sleep_estimate;
-				}
-			}
-			cgsleep_prepare_r(&usbdev->cgt_last_write);
-			usbdev->last_write_siz = bufsiz;
 		}
 		err = usb_bulk_transfer(usbdev->handle, intinfo, epinfo,
-					(unsigned char *)buf, bufsiz, &sent, timeout,
+					(unsigned char *)buf, tosend, &sent, timeout,
 					cgpu, MODE_BULK_WRITE, cmd, first ? SEQ0 : SEQ1,
 					false);
 		cgtime(&tv_finish);
@@ -2926,26 +2881,6 @@ int __usb_transfer(struct cgpu_info *cgpu, uint8_t request_type, uint8_t bReques
 
 	USBDEBUG("USB debug: @_usb_transfer() buf=%s", bin2hex(buf, (size_t)siz));
 
-	if (usbdev->usecps) {
-		if (usbdev->last_write_siz) {
-			cgtimer_t now, already_done;
-			double sleep_estimate;
-			double write_time = (double)(usbdev->last_write_siz) /
-					    (double)(usbdev->cps) * 1000;
-
-			cgtimer_time(&now);
-			cgtimer_sub(&now, &usbdev->cgt_last_write, &already_done);
-			sleep_estimate = write_time - cgtimer_to_ms(&already_done);
-
-			if (sleep_estimate > 0.0) {
-				cgsleep_ms_r(&usbdev->cgt_last_write, write_time);
-				cgpu->usbinfo.write_delay_count++;
-				cgpu->usbinfo.total_write_delay += sleep_estimate;
-			}
-		}
-		cgsleep_prepare_r(&usbdev->cgt_last_write);
-		usbdev->last_write_siz = siz;
-	}
 	STATS_TIMEVAL(&tv_start);
 	err = usb_control_transfer(cgpu, usbdev->handle, request_type, bRequest,
 				   wValue, wIndex, buf, (uint16_t)siz, timeout);
@@ -3009,22 +2944,6 @@ int _usb_transfer_read(struct cgpu_info *cgpu, uint8_t request_type, uint8_t bRe
 
 	*amount = 0;
 
-	if (usbdev->usecps && usbdev->last_write_siz) {
-		cgtimer_t now, already_done;
-		double sleep_estimate;
-		double write_time = (double)(usbdev->last_write_siz) /
-				    (double)(usbdev->cps) * 1000;
-
-		cgtimer_time(&now);
-		cgtimer_sub(&now, &usbdev->cgt_last_write, &already_done);
-		sleep_estimate = write_time - cgtimer_to_ms(&already_done);
-
-		if (sleep_estimate > 0.0) {
-			cgsleep_ms_r(&usbdev->cgt_last_write, write_time);
-			cgpu->usbinfo.read_delay_count++;
-			cgpu->usbinfo.total_read_delay += sleep_estimate;
-		}
-	}
 	memset(tbuf, 0, 64);
 	STATS_TIMEVAL(&tv_start);
 	err = usb_control_transfer(cgpu, usbdev->handle, request_type, bRequest,