>
>
> From: Matthew Bright [mailto:matthew.bri...@alliedtelesis.co.nz]
> Sent: Wednesday, June 22, 2016 11:56 AM
> To: Rajesh Bhagat <rajesh.bha...@nxp.com>; ma...@denx.de
> Cc: u-boot@lists.denx.de; Chris Packham <chris.pack...@alliedtelesis.co.nz>;
> Mark Tomlinson <mark.tomlin...@alliedtelesis.co.nz>
> Subject: comments: [PATCH v7 3/3] common: usb_storage: Implement logic to
> calculate optimal usb maximum trasfer blocks
>
Hello Matt,
Thanks for the review.
Hello Marek,
Would need your go ahead for changes.
> Hi Rajesh & Marek
>
> I have spend the last couple of days testing this patch and have a few review
> comments:
>
> On 06/16/2016 12:35 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 defines USB_MIN_XFER_BLK/USB_MAX_XFER_BLK 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 and max = 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>
> > Reviewed-by: Simon Glass <sjg at chromium.org>
> > ---
> > Changes in v7:
> > - None
> >
> > Changes in v6:
> > - Adds paranthesis around macro variables
> > - Removes extra ternary operator from dec_cur_xfer_blks
> > - Clamps the size to min(blks, USB_MAX_XFER_BLK) in inc_cur_xfer_blks
> >
> > Changes in v5:
> > - None
> >
> > Changes in v4:
> > - Adds udev paramater in dec/inc_cur_xfer_blks function and adds
> > sanity check on it.
> > - Changes type of pos varible to unsigned int in dec/inc_cur_xfer_blks
> > - Removes usage of pos varible from usb_stor_read/write
> >
> > Changes in v3:
> > - Adds cur_xfer_blks in struct usb_device to retain values
> > - Adds functions dec/inc_cur_xfer_blks to remove code duplication
> > - Moves check from macro to calling functions
> >
> > Changes in v2:
> > - Removes table to store blocks and use formula (1 << (12 + n)) - 1
> > - Adds logic to start from minimum, go to maximum in each read/write
> >
> > common/usb_storage.c | 66
> > ++++++++++++++++++++++++++++++++++++++++++++++++----
> > include/usb.h | 1 +
> > 2 files changed, 62 insertions(+), 5 deletions(-)
> >
> > diff --git a/common/usb_storage.c b/common/usb_storage.c
> > index a7d84bf..93b901c 100644
> > --- a/common/usb_storage.c
> > +++ b/common/usb_storage.c
> > @@ -106,11 +106,16 @@ struct us_data {
> > * enough free heap space left, but the SCSI READ(10) and WRITE(10)
> > commands are
> > * limited to 65535 blocks.
> > */
>
> Should this also include CONFIG_USB_XHCI? It appears
> that it is currently limited to the fixed 20 blocks.
>
I agree, same logic should be applied to CONFIG_XHCI also, which is also
very much required in case of CONFIG_DM_USB when both EHCI and XHCI are
defined. (As pointed in earlier email), Will take care in v8.
> > +#define USB_MIN_XFER_BLK 4095
>
> Where did this number 4095 come from; is 4095 blocks low enough?
This number was suggested by various experiments made in the thread you
mentioned,
as most of the pen drives worked with this number.
> It surprises me that USB_MIN_XFER_BLK has been set so high, when
> the linux default is 240 blocks and the windows default is 128
> blocks. Further, there appears to be some devices that will only
> support up to 64 blocks.
>
> http://lists.denx.de/pipermail/u-boot/2016-February/246250.html
>
> Maybe we could define a mid value for the transfer to start at;
> giving room to move in both directions dependent on the outcome
> of the transfer:
>
> #define USB_MIN_XFER_BLK 64
> #define USB_MID_XFER_BLK 4095
> #define USB_MAX_XFER_BLK 65535
>
> However the 5 second delay incurred for each ehci timeout would
> make working all the way down to 64 blocks painfully slow. Maybe
> if the first transfer fails (at 4095 blocks) then it should jump
> straight to 64 blocks and work its way up on each success.
>
> > #define USB_MAX_XFER_BLK 65535
> > #else
> > +#define USB_MIN_XFER_BLK 20
> > #define USB_MAX_XFER_BLK 20
> > #endif
> >
> > +#define GET_CUR_XFER_BLKS(blks) (LOG2(((blks) + 1) / (USB_MIN_XFER_BLK
> > + 1)))
> > +#define CALC_CUR_XFER_BLKS(pos) ((1 << (12 + (pos))) - 1)
> > +
> > #ifndef CONFIG_BLK
> > static struct us_data usb_stor[USB_MAX_STOR_DEV];
> > #endif
> > @@ -141,6 +146,44 @@ static void usb_show_progress(void)
> > debug(".");
> > }
> >
> > +static int dec_cur_xfer_blks(struct usb_device *udev)
> > +{
> > + /* decrease the cur_xfer_blks */
> > + unsigned int pos;
> > + unsigned short size;
> > +
> > + if (!udev)
> > + return -EINVAL;
> > +
> > + pos = GET_CUR_XFER_BLKS(udev->cur_xfer_blks);
> > + size = CALC_CUR_XFER_BLKS(pos - 1);
> > +
> > + if (size < USB_MIN_XFER_BLK)
> > + return -EINVAL;
> > +
> > + udev->cur_xfer_blks = size;
> > + return 0;
> > +}
> > +
> > +static int inc_cur_xfer_blks(struct usb_device *udev, lbaint_t blks)
> > +{
> > + /* try to increase the cur_xfer_blks */
> > + unsigned int pos;
> > + unsigned short size;
> > +
> > + if (!udev)
> > + return -EINVAL;
> > +
> > + pos = GET_CUR_XFER_BLKS(udev->cur_xfer_blks);
> > + size = CALC_CUR_XFER_BLKS(pos + 1);
> > +
> > + if (size > min(blks, (lbaint_t)USB_MAX_XFER_BLK))
> > + return -EINVAL;
> > +
> > + udev->cur_xfer_blks = size;
> > + return 0;
> > +}
> > +
> >
> > /*******************************************************************************
> > * show info on storage devices; 'usb start/init' must be invoked earlier
> > * as we only retrieve structures populated during devices initialization
> > @@ -1102,6 +1145,7 @@ static unsigned long usb_stor_read_write(struct
> > blk_desc *block_dev,
> > struct usb_device *udev;
> > struct us_data *ss;
> > int retry;
> > + bool retry_flag = false;
> > ccb *srb = &usb_ccb;
> > #ifdef CONFIG_BLK
> > struct blk_desc *block_dev;
> > @@ -1141,26 +1185,35 @@ static unsigned long usb_stor_read_write(struct
> > blk_desc *block_dev,
> > */
> > retry = 2;
> > srb->pdata = (unsigned char *)buf_addr;
> > - if (blks > USB_MAX_XFER_BLK)
> > - smallblks = USB_MAX_XFER_BLK;
> > + if (blks > udev->cur_xfer_blks)
> > + smallblks = udev->cur_xfer_blks;
> > else
> > smallblks = (unsigned short) blks;
> > retry_it:
> > - if (smallblks == USB_MAX_XFER_BLK)
> > + debug("%s: retry #%d, cur_xfer_blks %hu, smallblks %hu\n",
> > + __func__, retry, udev->cur_xfer_blks, smallblks);
> > + if (smallblks == udev->cur_xfer_blks)
> > usb_show_progress();
> > srb->datalen = block_dev->blksz * smallblks;
> > srb->pdata = (unsigned char *)buf_addr;
> > if (usb_read_write_10(srb, ss, start, smallblks, is_write)) {
> > debug("%s ERROR\n", __func__);
> > usb_request_sense(srb, ss);
> > - if (retry--)
> > + if (retry--) {
> > + if (!dec_cur_xfer_blks(udev))
> > + smallblks = udev->cur_xfer_blks;
>
> There is a potential error here:
>
> 1. A previous transfer has set udev->cur_xfer_blks=8191.
> 2. A current transfer with smallblks=10 fails (for whatever reason).
> 3. Both udev->cur_xfer_blks and smallblks are set to 4095 blocks.
> 4. The retry transfer will now occur with 4085 too many blocks.
>
> The smallblks should not be assigned here; instead the retry_it
> label should be moved to include the the four lines of code above
> it, which take into account the current blks value.
>
I agree, there is a potential error here. Will take care v8.
> > + retry_flag = true;
> > goto retry_it;
> > + }
> > blkcnt -= blks;
> > break;
> > }
> > start += smallblks;
> > blks -= smallblks;
> > buf_addr += srb->datalen;
> > +
> > + if (!retry_flag && !inc_cur_xfer_blks(udev, blks))
>
> There is a potential error here:
>
> 1. A previous transfer has set udev->cur_xfer_blks=8191, after a
> transfer with 16383 blocks caused an ehci time out error.
> 2. As retry_flag has been defined locally, all new transfers will
> again attempt to use 16383, which will cause another ehci time
> our error (each new transfer incurring another 5 second delay).
>
Defining retry_flag locally is very much required for the fact. Let us say you
performed a transfer which calculated the optimal blocks as 326767 due to
max size transferred. And now you are transferring more data, it should
not stick to last optimal size.
> I am not sure if this is the intended behavior. Maybe we do want
> to reattempt larger values on new transfers to weed out erroneous
> errors, however a 5 second delay on every new transfer is a steep
> price to pay for this. I suspect that once we have fallen back to
> a lower value, that we will want to stick to that lower value for
> all future transfers (on that specific device).
>
> A solution could be to replace the retry_flag with something
> like dev->xfer_throttled or dev->xfer_rate_limited.
>
> > + smallblks = udev->cur_xfer_blks;
> > } while (blks != 0);
> > ss->flags &= ~USB_READY;
> >
> > @@ -1169,7 +1222,7 @@ retry_it:
> > __func__, start, smallblks, buf_addr);
> >
> > usb_disable_asynch(0); /* asynch transfer allowed */
> > - if (blkcnt >= USB_MAX_XFER_BLK)
> > + if (blkcnt >= udev->cur_xfer_blks)
> > debug("\n");
> > return blkcnt;
> > }
> > @@ -1256,6 +1309,9 @@ int usb_storage_probe(struct usb_device *dev,
> > unsigned int ifnum,
> > break;
> > }
> >
> > + /* Initialize the current transfer blocks to minimum value */
> > + dev->cur_xfer_blks = USB_MIN_XFER_BLK;
> > +
> > /*
> > * We are expecting a minimum of 2 endpoints - in and out (bulk).
> > * An optional interrupt is OK (necessary for CBI protocol).
> > diff --git a/include/usb.h b/include/usb.h
> > index 02a0ccd..b815816 100644
> > --- a/include/usb.h
> > +++ b/include/usb.h
> > @@ -153,6 +153,7 @@ struct usb_device {
> > struct udevice *dev; /* Pointer to associated device */
> > struct udevice *controller_dev; /* Pointer to associated controller */
> > #endif
> > + unsigned short cur_xfer_blks; /* Current maximum transfer blocks */
> > };
> >
> > struct int_queue;
> > --
> > 2.6.2.198.g614a2ac
> >
Best Regards,
Rajesh Bhagat
>
> Cheers.
> - Matt Bright
>
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