On 26.12.2023 7.24, Prashanth K wrote:
On 22-12-23 11:40 am, Greg Kroah-Hartman wrote:
On Fri, Dec 22, 2023 at 11:29:01AM +0530, Prashanth K wrote:
On 15-12-23 06:12 pm, Greg Kroah-Hartman wrote:
On Tue, Dec 12, 2023 at 04:55:20PM +0530, Prashanth K wrote:
Upstream commit bac1ec551434 ("usb: xhci: Set quirk for
XHCI_SG_TRB_CACHE_SIZE_QUIRK") introduced a new quirk in XHCI
which fixes XHC timeout, which was seen on synopsys XHCs while
using SG buffers. But the support for this quirk isn't present
in the DWC3 layer.
We will encounter this XHCI timeout/hung issue if we run iperf
loopback tests using RTL8156 ethernet adaptor on DWC3 targets
with scatter-gather enabled. This gets resolved after enabling
the XHCI_SG_TRB_CACHE_SIZE_QUIRK. This patch enables it using
the xhci device property since its needed for DWC3 controller.
In Synopsys DWC3 databook,
Table 9-3: xHCI Debug Capability Limitations
Chained TRBs greater than TRB cache size: The debug capability
driver must not create a multi-TRB TD that describes smaller
than a 1K packet that spreads across 8 or more TRBs on either
the IN TR or the OUT TR.
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
What commit id does this fix?
This doesn't fix any commit as such, but adds the support for
XHCI_SG_TRB_CACHE_SIZE_QUIRK (which is present in XHCI layer) to DWC3 layer.
So this is a new feature?
How does this fit into the stable kernel rules?
This isn't a new feature. To give some background, upstream commit bac1ec551434 ("usb: xhci: Set quirk for XHCI_SG_TRB_CACHE_SIZE_QUIRK")
added a XHCI quirk which converts SG lists to CMA buffers/URBS if certain conditions aren't met. But they never enabled this xhci quirk
since no issues were hit at that time. So, the support for the above mentioned quirk is added from 5.11 kernel onwards, but was never enabled anywhere.
I remember this now.
Original series had three patches, two adding the feature to xhci, and one for dwc3 enabling it.
The xhci patches were fine and got in.
https://marc.info/?l=linux-usb&m=160570849625065&w=2
The last dwc3 patch had issues and never apparently got in
https://marc.info/?l=linux-usb&m=161008968009766&w=2
As this feature hasn't been enabled and code not widely run I think it would be better
to skip stable for now. Stable can be added later once this has been successfully running
in upstream for a while.
Thanks
Mathias
