On Fri, Dec 01, 2023 at 11:13:53AM -0500, Alan Stern wrote: > On Fri, Dec 01, 2023 at 03:47:05PM +0100, Hardik Gajjar wrote: > > There is a potential delay in notifying Linux USB drivers of downstream > > USB bus activity when connecting a high-speed or superSpeed device via the > > Microchip USB491x hub. This delay is due to the fixed bInterval value of > > 12 in the silicon of the Microchip USB491x hub. > > > > Microchip requested to ignore the device descriptor and decrease that > > value to 9 as it was too late to modify that in silicon. > > > > This patch speeds up the USB enummeration process that helps to pass > > Apple Carplay certifications and improve the User experience when utilizing > > the USB device via Microchip Multihost USB491x Hub. > > > > A new hub quirk HUB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL speeds up > > the notification process for Microchip USB491x hub by limiting > > the maximum bInterval value to 9. > > > > Signed-off-by: Hardik Gajjar <hgajjar@xxxxxxxxxxxxxx> > > --- > > changes since version 1: > > - Move implementation from config.c and quirk.c to hub.c as this is hub > > specific changes. > > - Improve commit message. > > - Link to v1 - https://lore.kernel.org/all/20231123081948.58776-1-hgajjar@xxxxxxxxxxxxxx/ > > > > changes since version 2: > > - Call usb_set_interface after updating the bInterval to Tell the HCD about modification > > - Link to v2 - https://lore.kernel.org/all/20231130084855.119937-1-hgajjar@xxxxxxxxxxxxxx/ > > --- > > drivers/usb/core/hub.c | 27 +++++++++++++++++++++++++++ > > 1 file changed, 27 insertions(+) > > > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > > index b4584a0cd484..b5ac29c5f016 100644 > > --- a/drivers/usb/core/hub.c > > +++ b/drivers/usb/core/hub.c > > @@ -47,12 +47,18 @@ > > #define USB_VENDOR_TEXAS_INSTRUMENTS 0x0451 > > #define USB_PRODUCT_TUSB8041_USB3 0x8140 > > #define USB_PRODUCT_TUSB8041_USB2 0x8142 > > +#define USB_VENDOR_MICROCHIP 0x0424 > > +#define USB_PRODUCT_USB4913 0x4913 > > +#define USB_PRODUCT_USB4914 0x4914 > > +#define USB_PRODUCT_USB4915 0x4915 > > #define HUB_QUIRK_CHECK_PORT_AUTOSUSPEND 0x01 > > #define HUB_QUIRK_DISABLE_AUTOSUSPEND 0x02 > > +#define HUB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL 0x08 > > Why use 0x08 instead of 0x04? And why not use BIT() as that's what these are. thanks, greg k-h
