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Since commit 760b3dffb0 ("qdl: Rework qdl_write to limit write sizes
to out_maxpktsize") outgoing transfers has been chunked into blocks of
wMaxPacketSize.
As reported by Wiktor Drewniak, Maksim Paimushkin, and Luca Weiss in [1]
there's huge benefits to be found in reverting this change, but out of
caution the limit was untouched.
With the transition to libusb, the throughput dropped another ~15% on my
machine. The numbers for HighSpeed and SuperSpeed are also in the same
ballpark.
With SuperSpeed, benchmarking of different chunk sizes in the megabyte
range shows improvement over these numbers in the range of 15-20x on the
same machine/board combination.
The bug report related to the reduction in size describes a host machine
running out of swiotlb, from the fact that we requested 1MB physically
contiguous memory. It's unclear if attempts was made to correct the
kernel's behavior. libusb does inquiry the capabilities of the kernel
and will split the buffer and submitting multiple URBs at once, as
needed. While no definitive guidance has been found, multiple sources
seems to recommend passing 1-2MB of buffer to libusb at a time. So,
let's move the default chunk size back up to 1MB and hope that libusb
resolves the reported problem.
Additionally, introduce a new option --out-chunk-size, which allow the
user to override the chunk size. This would allow any user to reduce the
size if needed, but also allow the value to be increased as needed.
[1] https://github.com/linux-msm/qdl/pull/39
Reported-by: Wiktor Drewniak
Reported-by: Maksim Paimushkin
Reported-by: Luca Weiss
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Qualcomm Download ================= This tool communicates with USB devices of id 05c6:9008 to upload a flash loader and use this to flash images. Usage: qdl <prog.mbn> [<program> <patch> ...] Building ======== In order to build the project you need libxml2 and libusb-1.0 headers and libraries, found in e.g. the libxml2-dev and libusb-1.0.0-dev packages With these installed run: make