From: Alan Stern <stern@rowland.harvard.edu>
To: Hardik Gajjar <hgajjar@de.adit-jv.com>
Cc: gregkh@linuxfoundation.org, corbet@lwn.net,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
erosca@de.adit-jv.com, tj@kernel.org, paulmck@kernel.org,
Martin.Mueller5@de.bosch.com
Subject: Re: [PATCH v5 2/2] usb: hub: Add quirk to decrease IN-ep poll interval for Microchip USB491x hub
Date: Tue, 5 Dec 2023 13:22:09 -0500 [thread overview]
Message-ID: <1773e17b-a94e-4101-8881-54e33fb700d6@rowland.harvard.edu> (raw)
In-Reply-To: <20231205181829.127353-2-hgajjar@de.adit-jv.com>
On Tue, Dec 05, 2023 at 07:18:29PM +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@de.adit-jv.com>
> ---
> 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@de.adit-jv.com/
>
> 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@de.adit-jv.com/
>
> changes since version 3:
> - Change HUB_QUIRK_REDUCE_FRAME_INTR_BINTERVAL value from 0x08 to 0x04
> - Link to v3 - https://lore.kernel.org/all/20231201144705.97385-1-hgajjar@de.adit-jv.com/
>
> changes since version 4:
> - change quirk hardcoded value to BIT() Macro
> - Link to v4 - https://lore.kernel.org/all/20231204073834.112509-1-hgajjar@de.adit-jv.com/
> ---
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
next prev parent reply other threads:[~2023-12-05 18:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-05 18:18 [PATCH 1/2] usb: hub: Replace hardcoded quirk value with BIT() macro Hardik Gajjar
2023-12-05 18:18 ` [PATCH v5 2/2] usb: hub: Add quirk to decrease IN-ep poll interval for Microchip USB491x hub Hardik Gajjar
2023-12-05 18:22 ` Alan Stern [this message]
2023-12-05 18:21 ` [PATCH 1/2] usb: hub: Replace hardcoded quirk value with BIT() macro Alan Stern
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