[U-Boot] [PATCH 1/2] common: usb_storage : Implement logic to calculate optimal usb maximum trasfer blocks
Rajesh Bhagat
rajesh.bhagat at nxp.com
Wed Jun 1 05:47:29 CEST 2016
> -----Original Message-----
> From: Marek Vasut [mailto:marex at denx.de]
> Sent: Tuesday, May 31, 2016 5:27 PM
> To: Rajesh Bhagat <rajesh.bhagat at nxp.com>; u-boot at lists.denx.de
> Cc: sjg at chromium.org; york sun <york.sun at nxp.com>; Sriram Dash
> <sriram.dash at nxp.com>
> Subject: Re: [PATCH 1/2] common: usb_storage : Implement logic to calculate
> optimal usb maximum trasfer blocks
>
> On 05/31/2016 05:23 AM, Rajesh Bhagat wrote:
> >
> >
> >> -----Original Message-----
> >> From: Marek Vasut [mailto:marex at denx.de]
> >> Sent: Tuesday, May 31, 2016 5:12 AM
> >> To: Rajesh Bhagat <rajesh.bhagat at nxp.com>; u-boot at lists.denx.de
> >> Cc: sjg at chromium.org; york sun <york.sun at nxp.com>; Sriram Dash
> >> <sriram.dash at nxp.com>
> >> Subject: Re: [PATCH 1/2] common: usb_storage : Implement logic to
> >> calculate optimal usb maximum trasfer blocks
> >>
> >> On 05/30/2016 01:23 PM, Rajesh Bhagat wrote:
> >>> Implements the logic to calculate the optimal usb maximum trasfer
> >>> blocks instead of sending USB_MAX_XFER_BLK blocks which is 65535 and
> >>> 20 in case of EHCI and other USB protocols respectively.
> >>>
> >>> It adds an array of trasfer blocks that should be checked for
> >>> success starting from minimum to maximum, and rest of the read/write
> >>> are performed with that optimal value. It tries to increase/decrease
> >>> the blocks in follwing scenarios:
> >>>
> >>> 1.decrease blocks: when read/write for a particular number of blocks
> >>> fails.
> >>> 2. increase blocks: when read/write for a particular number of
> >>> blocks pass and amount left to trasfer is greater than current
> >>> number of blocks.
> >>>
> >>> Currently changes are done for EHCI where min = 4096 andmax = 65535
> >>> is taken. And for other cases code is left unchanged by keeping min
> >>> = max = 20.
> >>>
> >>> Signed-off-by: Sriram Dash <sriram.dash at nxp.com>
> >>> Signed-off-by: Rajesh Bhagat <rajesh.bhagat at nxp.com>
> >>> ---
> >>> common/usb_storage.c | 54
> >> ++++++++++++++++++++++++++++++++++++++++----------
> >>> 1 file changed, 43 insertions(+), 11 deletions(-)
> >>>
> >>> diff --git a/common/usb_storage.c b/common/usb_storage.c index
> >>> 7e6e52d..7b5ad07 100644
> >>> --- a/common/usb_storage.c
> >>> +++ b/common/usb_storage.c
> >>> @@ -101,16 +101,15 @@ struct us_data { };
> >>>
> >>> #ifdef CONFIG_USB_EHCI
> >>> -/*
> >>> - * The U-Boot EHCI driver can handle any transfer length as long as
> >>> there is
> >>> - * enough free heap space left, but the SCSI READ(10) and WRITE(10)
> >>> commands are
> >>> - * limited to 65535 blocks.
> >>> - */
> >>> -#define USB_MAX_XFER_BLK 65535
> >>> +#define USB_XFER_BLK_TBL_SZ 5
> >>> +static unsigned short usb_xfer_blk_tbl[5] = {4096, 8192, 16384,
> >>> +32768, 65535};
> >>
> >> You should stick to using one block less than the power of two, the
> >> controllers react to that a bit better.
> >
> > Hello Marek,
> >
> > I agree to above point, Will change the logic to use one block less
> > than power of two i.e. 4095, 8191... 65535
> >
> >> Each value in this table can then be calculated really trivially, it's:
> >>
> >> (1 << (12 + n)) - 1
> >>
> >
> > Prior to current implementation, I created USB_MIN_XFER_BLK=4096 and
> > USB_MAX_XFER_BLK=65535 macros. And started the logic to multiple and
> > divide by two to reach USB_MAX_XFER_BLK. Then thought, calculation
> > would be costlier than indexing an array.
Hello Marek,
>
> Since the numbers are 16bit tops, they will most likely end up being optimized to mov
> rN, #imm16 or mov rN, imm16 + sub rN, #1 . That's two local instructions tops,
> which will always be at least as fast as any memory fetch.
>
Ok, I agree to your point. Will change the logic to use above formula as mentioned
by you in v2.
> > Please comment.
> >
> >> You also don't need such static data.
> >>
> >
> > Let me share the background for keeping this variable, It is taken to
> > store the last optimal value for next read/write operation. And these
> > value is reset to minimum when another USB device is connected.
>
> Consider the scenario where you have two sticks plugged in and mix reading from
> both. Your approach with static variable will fail miserably.
>
You are right, I missed it completely. Above logic would have been possible if at time
of changing the current device "usb dev ..", I reset the value to minimum again as we
I have done when new device is connected. But "usb dev .." doesn’t seem to mapped
to common/usb_storage.c code. Hence, it is difficult to retain value keeping a static
variable.
I will change the logic to start from minimum and try to go to maximum in every read/write
in v2.
Best Regards,
Rajesh Bhagat
> > Refer below log:
> >
> > 1st time (Iterated over all the possible size) => mw 81000000 55555555
> > 4000000; mw a0000000 aaaaaaaa 4000000; usb write a0000000 0 80000; usb
> > read 81000000 0 80000; cmp.b a0000000 81000000 10000000;
> >
> > USB write: device 0 block # 0, count 524288 ... usb_read: retry #2,
> > xfer_blk 4096, smallblks 4096
> > usb_read: retry #2, xfer_blk 8192, smallblks 8192
> > usb_read: retry #2, xfer_blk 16384, smallblks 16384
> > usb_read: retry #2, xfer_blk 32768, smallblks 32768
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 4103
> > 524288 blocks write: OK
> >
> > 2nd time (It started form 65535 blocks as it is last optimal value) =>
> > mw 81000000 55555555 4000000; mw a0000000 aaaaaaaa 4000000; usb write
> > a0000000 0 80000; usb read 81000000 0 80000; cmp.b a0000000 81000000
> > 10000000;
> >
> > USB write: device 0 block # 0, count 524288 ... usb_read: retry #2,
> > xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 65535
> > usb_read: retry #2, xfer_blk 65535, smallblks 8
> > 524288 blocks write: OK
> >
> > And I observed this value is different for read/write, Hence second
> > patch is sent for handle that situation.
> >
> > Best Regards,
> > Rajesh Bhagat
> >
> >>> #else
> >>> -#define USB_MAX_XFER_BLK 20
> >>> +#define USB_XFER_BLK_TBL_SZ 1
> >>> +static unsigned short usb_xfer_blk_tbl[1] = {20};
> >>> #endif
> >>>
> >>> +static unsigned short USB_MAX_XFER_BLK;
> >>
> >> This value is different on per-device basis, how can it be static data ?
> >>
> >>> #ifndef CONFIG_BLK
> >>> static struct us_data usb_stor[USB_MAX_STOR_DEV]; #endif @@
> >>> -1117,7
> >>> +1116,8 @@ static unsigned long usb_stor_read(struct blk_desc
> >>> +*block_dev,
> >> lbaint_t blknr,
> >>> unsigned short smallblks;
> >>> struct usb_device *udev;
> >>> struct us_data *ss;
> >>> - int retry;
> >>> + int retry, next = LOG2((USB_MAX_XFER_BLK + 1) /
> usb_xfer_blk_tbl[0]);
> >>> + bool retry_flag = false;
> >>> ccb *srb = &usb_ccb;
> >>> #ifdef CONFIG_BLK
> >>> struct blk_desc *block_dev;
> >>> @@ -1158,6 +1158,8 @@ static unsigned long usb_stor_read(struct
> >>> blk_desc
> >> *block_dev, lbaint_t blknr,
> >>> else
> >>> smallblks = (unsigned short) blks;
> >>> retry_it:
> >>> + debug("usb_read: retry #%d, xfer_blk %hu, smallblks %hu\n",
> >>> + retry, USB_MAX_XFER_BLK, smallblks);
> >>> if (smallblks == USB_MAX_XFER_BLK)
> >>> usb_show_progress();
> >>> srb->datalen = block_dev->blksz * smallblks; @@ -1165,14 +1167,26
> >>> @@ retry_it:
> >>> if (usb_read_10(srb, ss, start, smallblks)) {
> >>> debug("Read ERROR\n");
> >>> usb_request_sense(srb, ss);
> >>> - if (retry--)
> >>> + if (retry--) {
> >>> + /* decrease the USB_MAX_XFER_BLK */
> >>> + if (next > 0) {
> >>> + smallblks = usb_xfer_blk_tbl[--next];
> >>> + USB_MAX_XFER_BLK = smallblks;
> >>> + }
> >>> + retry_flag = true;
> >>> goto retry_it;
> >>> + }
> >>> blkcnt -= blks;
> >>> break;
> >>> }
> >>> start += smallblks;
> >>> blks -= smallblks;
> >>> buf_addr += srb->datalen;
> >>> +
> >>> + /* try to increase the USB_MAX_XFER_BLK */
> >>> + if (next < USB_XFER_BLK_TBL_SZ - 1)
> >>> + if (!retry_flag && usb_xfer_blk_tbl[next + 1] <= blks)
> >>> + USB_MAX_XFER_BLK = usb_xfer_blk_tbl[++next];
> >>> } while (blks != 0);
> >>> ss->flags &= ~USB_READY;
> >>>
> >>> @@ -1199,7 +1213,8 @@ static unsigned long usb_stor_write(struct
> >>> blk_desc
> >> *block_dev, lbaint_t blknr,
> >>> unsigned short smallblks;
> >>> struct usb_device *udev;
> >>> struct us_data *ss;
> >>> - int retry;
> >>> + int retry, next = LOG2((USB_MAX_XFER_BLK + 1) /
> usb_xfer_blk_tbl[0]);
> >>> + bool retry_flag = false;
> >>> ccb *srb = &usb_ccb;
> >>> #ifdef CONFIG_BLK
> >>> struct blk_desc *block_dev;
> >>> @@ -1244,6 +1259,8 @@ static unsigned long usb_stor_write(struct
> >>> blk_desc
> >> *block_dev, lbaint_t blknr,
> >>> else
> >>> smallblks = (unsigned short) blks;
> >>> retry_it:
> >>> + debug("usb_write: retry #%d, xfer_blk %hu, smallblks %hu\n",
> >>> + retry, USB_MAX_XFER_BLK, smallblks);
> >>> if (smallblks == USB_MAX_XFER_BLK)
> >>> usb_show_progress();
> >>> srb->datalen = block_dev->blksz * smallblks; @@ -1251,14 +1268,26
> >>> @@ retry_it:
> >>> if (usb_write_10(srb, ss, start, smallblks)) {
> >>> debug("Write ERROR\n");
> >>> usb_request_sense(srb, ss);
> >>> - if (retry--)
> >>> + if (retry--) {
> >>> + /* decrease the USB_MAX_XFER_BLK */
> >>> + if (next > 0) {
> >>> + smallblks = usb_xfer_blk_tbl[--next];
> >>> + USB_MAX_XFER_BLK = smallblks;
> >>> + }
> >>> + retry_flag = true;
> >>> goto retry_it;
> >>> + }
> >>> blkcnt -= blks;
> >>> break;
> >>> }
> >>> start += smallblks;
> >>> blks -= smallblks;
> >>> buf_addr += srb->datalen;
> >>> +
> >>> + /* try to increase the USB_MAX_XFER_BLK */
> >>> + if (next < USB_XFER_BLK_TBL_SZ - 1)
> >>> + if (!retry_flag && usb_xfer_blk_tbl[next + 1] <= blks)
> >>> + USB_MAX_XFER_BLK = usb_xfer_blk_tbl[++next];
> >>> } while (blks != 0);
> >>> ss->flags &= ~USB_READY;
> >>>
> >>> @@ -1331,6 +1360,9 @@ int usb_storage_probe(struct usb_device *dev,
> >>> unsigned
> >> int ifnum,
> >>> break;
> >>> }
> >>>
> >>> + /* Initialize the current transfer blocks to minimum value */
> >>> + USB_MAX_XFER_BLK = usb_xfer_blk_tbl[0];
> >>> +
> >>> /*
> >>> * We are expecting a minimum of 2 endpoints - in and out (bulk).
> >>> * An optional interrupt is OK (necessary for CBI protocol).
> >>>
> >>
> >>
> >> --
> >> Best regards,
> >> Marek Vasut
>
>
> --
> Best regards,
> Marek Vasut
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