On 02/23/2016 07:38 AM, Hannes Schmelzer wrote: > On 22.02.2016 18:59, Fabio Estevam wrote: >> On Mon, Feb 22, 2016 at 2:51 PM, Maxime Jayat <jayatmax...@gmail.com> >> wrote: >> >>> Hello, >>> I was hit by the same problem, where my USB SD card reader would timeout >>> in U-boot when reading a large file (16 MB). Changing USB_MAX_XFER_BLK >>> to 32767 fixed the problem but I investigated a little more. >>> I was curious to see what the Linux kernel used, because it had no >>> problem reading the file. In Linux, USB_MAX_XFER_BLK corresponds to >>> max_sector in the scsiglue, which is set to 240 blocks per transfer by >>> default, and is tunable via sysfs. >>> There is also a list of unusual devices which needs no higher than 64 >>> blocks per transfer. >>> The linux USB FAQ has a very interesting entry about this which explains >>> the rationale for this value: >>> http://www.linux-usb.org/FAQ.html#i5 >>> >>> FWIW: my USB card reader is >>> 0bda:0119 Realtek Semiconductor Corp. Storage Device (SD card reader) >>> >>> I've benchmarked in U-boot the time impact of this change. >>> For reading my 16764395 bytes file: >>> USB_MAX_XFER_BLK Read duration (as reported by U-boot): >>> 64 3578 ms >>> 128 2221 ms >>> 240 1673 ms >>> 32767 1020 ms >>> 65535 974 ms >>> >>> So there is definitely a strong impact for lower values. >> Ok, so with a USB_MAX_XFER_BLK size of 32767 there is not so much of a >> performance impact. >> >> Looks like that changing USB_MAX_XFER_BLK from 65535 to 32767 is the >> way to go. > I have configured a value of 8191 some few weeks ago on my zynq board, > there was no negative feedback until yesterday :-( > > A colleague of mine told me, that his USB-stick doesn't work. I had a look. > > Vendor: 0x1307 Product 0x0165 Version 1.0 > I had to reduce the USB_MAX_XFER_BLK downto 2048 to make it work. > > I'm not the big usb-expert ... but would it be possible to move away > from this > #define to some variable which is adapted to the lowest value on the bus. > Is it possible at all to get to right value out of some register ?
We will probably need a quirk table and for the crappy USB sticks, we will just have to use lower maximum xfer size. I would suggest to add an environment variable, which would allow to override the max xfer size. This would help in case the user had a device, which does need a quirk, but is not yet in a quirk table ; as a temporary work around of course. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
