On Thu, Nov 23, 2023 at 09:19:48AM +0100, Hardik Gajjar wrote: > There is a potential delay in announcing downstream USB bus activity to > Linux USB drivers due to the default interrupt endpoint having a poll > interval of 256ms. > > Microchip has recommended ignoring the device descriptor and reducing > that value to 32ms, as it was too late to modify it in silicon. > > This patch aims to speed up the USB enumeration process, facilitating > the successful completion of Apple CarPlay certifications and enhancing > user experience when utilizing USB devices through the Microchip Multihost > Hub. > > A new quirk, USB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL, accelerates the > notification process by changing the Endpoint interrupt poll interval > from 256ms to 32ms. But this is meant to apply only to hubs, right? So shouldn't it be a HUB_QUIRK_32_MS_INTR_INTERVAL macro, used in hub.c's hub_id_table, rather than a general USB quirk? > Signed-off-by: Hardik Gajjar <hgajjar@xxxxxxxxxxxxxx> > --- > Documentation/admin-guide/kernel-parameters.txt | 4 ++++ > drivers/usb/core/config.c | 8 ++++++++ > drivers/usb/core/quirks.c | 11 +++++++++++ > include/linux/usb/quirks.h | 5 +++++ > 4 files changed, 28 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 65731b060e3f..6b0a66f0e6bf 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -6908,6 +6908,10 @@ > pause after every control message); > o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra > delay after resetting its port); > + p = USB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL (Set > + bInterval to a Maximum of 9 to Reduce > + default Poll Rate from 256 ms to > + 32 ms); 256 ms and 32 ms are _periods_ (or intervals), not _rates_. bInterval=9 corresponds to 32 ms only for High Speed and SuperSpeed* devices. For Low and Full Speed it corresponds to 9 ms. Explanatory comments should strive not to be misleading. Alan Stern
