On Thu, Nov 23, 2023 at 01:17:03PM -0500, Alan Stern wrote: > 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? Thank you, Alan, for the feedback. To confirm my understanding, are you suggesting moving all implementations to hub.c, adding the hub-specific quirk, and using the same quirk to update the bInterval value parsed by usb_get_configuration() in usb_enumerate_device()?" > > > 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
