Hi Jim,
On Thu, Jul 26, 2012 at 10:20:48 PM, Jim Shimer wrote:
I'm seeing a 5ms delay in usb_stor_BBB_transport, which occurs every 10K of data for fatload usb or 500ms of delay per 1MB of image size. This adds up to quite a bit of delay if you're loading a large ramdisk.
Does anyone know what the reason for the 5ms delay really is? I'm assuming that this delay is to debounce the 5V/100ma USB power up. I made some modification, where the delay is skipped if the device has already been queried as ready. This has save me 500ms/M on fatload times (eg, 140M=70seconds). Is there anything wrong with this tweak?
Here's a diff of what I've done to get the performance I need:
--- usb_storage.c.orig 2012-07-26 16:06:40.775251000 -0400 +++ usb_storage.c 2012-07-26 13:49:36.000000000 -0400 @@ -132,6 +132,7 @@ static block_dev_desc_t usb_dev_desc[USB struct us_data; typedef int (*trans_cmnd)(ccb *cb, struct us_data *data); typedef int (*trans_reset)(struct us_data *data); +typedef enum us_status { USB_NOT_READY, USB_READY} us_status;
struct us_data { struct usb_device *pusb_dev; /* this usb_device */ @@ -154,6 +155,7 @@ struct us_data { ccb *srb; /* current srb */ trans_reset transport_reset; /* reset routine */ trans_cmnd transport; /* transport routine */
us_status status;};
static struct us_data usb_stor[USB_MAX_STOR_DEV]; @@ -691,7 +693,10 @@ int usb_stor_BBB_transport(ccb *srb, str usb_stor_BBB_reset(us); return USB_STOR_TRANSPORT_FAILED; }
wait_ms(5);
if(us->status != USB_READY){wait_ms(5);} pipein = usb_rcvbulkpipe(us->pusb_dev, us->ep_in); pipeout = usb_sndbulkpipe(us->pusb_dev, us->ep_out); /* DATA phase + error handling */@@ -957,7 +962,10 @@ static int usb_test_unit_ready(ccb *srb, srb->datalen = 0; srb->cmdlen = 12; if (ss->transport(srb, ss) == USB_STOR_TRANSPORT_GOOD)
{ss->status = USB_READY; return 0;} usb_request_sense(srb, ss); wait_ms(100); } while (retries--);@@ -965,6 +973,11 @@ static int usb_test_unit_ready(ccb *srb, return -1; }
+static void usb_set_unit_not_ready(struct us_data *ss) +{
ss->status = USB_NOT_READY;+}
static int usb_read_capacity(ccb *srb, struct us_data *ss) { int retry; @@ -1108,6 +1121,7 @@ retry_it: blks -= smallblks; buf_addr += srb->datalen; } while (blks != 0);
usb_set_unit_not_ready((struct us_data *)dev->privptr); USB_STOR_PRINTF("usb_read: end startblk %lx, blccnt %x buffer%lx\n", start, smallblks, buf_addr); @@ -1188,6 +1202,7 @@ retry_it: blks -= smallblks; buf_addr += srb->datalen; } while (blks != 0);
usb_set_unit_not_ready((struct us_data *)dev->privptr); USB_STOR_PRINTF("usb_write: end startblk %lx, blccnt %x buffer%lx\n", start, smallblks, buf_addr); @@ -1398,6 +1413,7 @@ int usb_stor_get_info(struct usb_device cap[0] = 2880; cap[1] = 0x200; }
usb_set_unit_not_ready((struct us_data *)dev->privptr); USB_STOR_PRINTF("Read Capacity returns: 0x%lx, 0x%lx\n", cap[0], cap[1]);#if 0
I'd appreciate any feedback. Regards
I have not looked into this delay issue, but I had similar performance issues that I fixed with the following series: http://patchwork.ozlabs.org/patch/172052/ http://patchwork.ozlabs.org/patch/172204/ http://patchwork.ozlabs.org/patch/172054/ http://patchwork.ozlabs.org/patch/172055/ http://patchwork.ozlabs.org/patch/172056/
Your suggestion is interesting and might be a complement to my series. I don't have time to check its correctness right now, but I'll try soon.
Best regards, Benoît