sp193
commented
2 months ago There is a hardware issue in the USB OHCI controller, which causes problems when a certain transfer size is used for outbound flows. The normal version will do some workaround, while the "aligned" version does not (assumption: you provide an aligned memory buffer, which will thus not meet the condition for the hardware bug). For more details, you may need to refer to the official documentation.
Actually, I did try using the normal function and I recall it somewhat worked. But as Sony remarked, the internal workaround might result in issues with some devices. I recall that writes resulted in corruption on my SanDisk.
Therefore, writes were left to use the aligned variant.
fjtrujy
👋 I have been facing some issues with USB drivers when using
fwritefrom unaligned 4-byte buffers... Given the next example:It works as expected, however, if we replace
unsigned char *dummy_content_offset = dummy_contentwithunsigned char *dummy_content_offset = dummy_content + 6to force having an offset, it fails due to alignment issues on the USB driver.Compiling
PS2SDKwithDEBUG=1we can have some extra information.Without
offset:With
offset:If you see, we start to suffer errors likes this one:
Where
bulk data transfer 262262=0x106which isfrom
iop/usb/usbd/include/usbd.hOfficial documentation for FatFs - Generic FAT Filesystem Module mentioned in the
dreadanddwriteinformation about possible alignment issues: http://elm-chan.org/fsw/ff/doc/dread.html http://elm-chan.org/fsw/ff/doc/dwrite.htmlThis is something that I actually see reflected on the execution... Let's follow the callback functions:
Buffer is aligned till it reaches the
iop/fs/bdmfs_fatfs/src/ff.c ==> f_writefunction where it plays with buffer index, producing already an unaligned buffer. Is important to mention that code fromf_writebelong tofswlibrary. So, why it is failing? It fails because on thesceUsbdTransferPipewe have the next condition:If you see it check if data is aligned with
((u32)data & 3)), but it only check it if theep->alignFlagis different that0.This flag is set when registering the endpoints
We generate 2 different endpoint, one for reading from USB (INPUT), and another one for writing (
OUTPUT).If we see how this is done is through the function
usb_bulk_probeEndpointiniop/usb/usbmass_bd/src/usb_mass.cIf you take a look it uses
sceUsbdOpenPipeAlignedforUSB_DIR_OUT. ThesceUsbdOpenPipeAlignedis the one that set thealignFlag = 1, which triggers the condition that fails later on theiop/usb/usbd/src/interface.c ==> sceUsbdTransferPipe.I don't know how to fix it as I don't have enough experience with drivers at that low level... however, I hope all this information is useful for you...
Pinging @sp193 @rickgaiser @davidgfnet @uyjulian as I know you have experience with these kinds of things.
Cheers.