Re: FYI: RPi4B's and such: VLI_SS_BULK_OUT_BUG quirk handling vs. VL805 (linux example)
Hans Petter Selasky <[email protected]>
| Newsgroups | gmane.os.freebsd.devel.arm |
|---|---|
| Message-ID | <[email protected]> |
On 9/17/22 18:09, Mark Millard wrote: > https://github.com/raspberrypi/linux/pull/5173 reports: > > QUOTE > After several months back-and-forth with VIA, we have a candidate root-cause for #4844 and a suggested fix. My known-bad pendrive now gets written to endlessly without suffering data corruption. > END QUOTE > > and: > > QUOTE > usb: xhci: expand mitigations for VLI_SS_BULK_OUT_BUG quirk … c9e051a > > The VL805 can cause data corruption if a SS Bulk OUT endpoint enters a > flow-control condition and there are TRBs in the transfer ring that are > not an integral size of wMaxPacket and the endpoint is behind one or more > hubs. > > This is frequently the case encountered when FAT32 filesystems are > present on mass-storage devices with cluster sizes of 1 sector, and the > filesystem is being written to with an aggregate of small files. > > The initial implementation of this quirk separated TRBs that didn't > adhere to this limitation into two - the first a multiple of wMaxPacket > and the second the 512-byte remainder - in an attempt to force TD > fragments to align with packet boundaries. This reduced the incidence > rate of data corruption but did not resolve it. > > The fix as recommended by VIA is to disable bursts if this sequence of > TRBs can occur. > > Limit turning off bursts to just USB mass-storage devices by searching > the device's configuration for an interface with a class type of > USB_CLASS_MASS_STORAGE. > > Signed-off-by: Jonathan Bell <[email protected]> > END QUOTE > > and the drivers/usb/host/xhci-mem.c change has the comments: > > > /* > * VL805 errata - Bulk OUT bursts to superspeed mass-storage > * devices behind hub ports can cause data corruption with > * non-wMaxPacket-multiple transfers. > */ > . . . > > /* > * Slight hack - look at interface altsetting 0, which > * should be the UMS bulk-only interface. If the class > * matches, then we disable out bursts for all OUT > * endpoints because endpoint assignments may change > * between alternate settings. > */ > > === > Mark Millard > marklmi at yahoo.com > > Hi, It doesn't make sense that this only applies to USB mass storage devices. Doesn't it apply to all SuperSpeed USB BULK transfers? What about other OS'es, do they also get a fix? --HPS