From: Peter Chen <peter.chen@nxp.com>
To: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Cc: "balbi@kernel.org" <balbi@kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] usb: gadget: epautoconf: claim smallest endpoints first
Date: Tue, 30 Jun 2020 01:58:19 +0000 [thread overview]
Message-ID: <20200630015843.GB12443@b29397-desktop> (raw)
In-Reply-To: <20200629201845.28138-1-ruslan.bilovol@gmail.com>
On 20-06-29 23:18:45, Ruslan Bilovol wrote:
> UDC hardware may have endpoints with different maxpacket
> size. Current endpoint matching code takes first matching
> endpoint from the list.
>
> It's always possible that gadget allocates endpoints for
> small transfers (maxpacket size) first, then larger ones.
> That works fine if all matching UDC endpoints have same
> maxpacket size or are big enough to serve that allocation.
>
> However, some UDCs have first endpoints in the list with
> bigger maxpacket size, whereas last endpoints are much
> smaller. In this case endpoint allocation will fail for
> the gadget (which allocates smaller endpoints first) on
> final endpoint allocations.
>
> To make endpoint allocation fair, pick up smallest
> matching endpoints first, leaving bigger ones for
> heavier applications.
>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> ---
>
> v2: rebased onto latest balbi/next branch
>
> drivers/usb/gadget/epautoconf.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/gadget/epautoconf.c b/drivers/usb/gadget/epautoconf.c
> index 1eb4fa2e623f..6c453b5d87bb 100644
> --- a/drivers/usb/gadget/epautoconf.c
> +++ b/drivers/usb/gadget/epautoconf.c
> @@ -66,7 +66,7 @@ struct usb_ep *usb_ep_autoconfig_ss(
> struct usb_ss_ep_comp_descriptor *ep_comp
> )
> {
> - struct usb_ep *ep;
> + struct usb_ep *ep, *ep_min = NULL;
>
> if (gadget->ops->match_ep) {
> ep = gadget->ops->match_ep(gadget, desc, ep_comp);
> @@ -74,14 +74,27 @@ struct usb_ep *usb_ep_autoconfig_ss(
> goto found_ep;
> }
>
> - /* Second, look at endpoints until an unclaimed one looks usable */
> + /*
> + * Second, look at endpoints until an unclaimed one looks usable.
> + * Try to find one with smallest maxpacket limit, leaving larger
> + * endpoints for heavier applications
> + */
> list_for_each_entry (ep, &gadget->ep_list, ep_list) {
> - if (usb_gadget_ep_match_desc(gadget, ep, desc, ep_comp))
> - goto found_ep;
> + if (usb_gadget_ep_match_desc(gadget, ep, desc, ep_comp)) {
> + if (desc->wMaxPacketSize == 0)
> + goto found_ep;
Why you do special handling for this? You still could give the smallest
maxpacket_limit EP for it, right?
Peter
> + else if (!ep_min)
> + ep_min = ep;
> + else if (ep->maxpacket_limit < ep_min->maxpacket_limit)
> + ep_min = ep;
> + }
> }
>
> /* Fail */
> - return NULL;
> + if (!ep_min)
> + return NULL;
> +
> + ep = ep_min;
> found_ep:
>
> /*
> --
> 2.17.1
>
--
Thanks,
Peter Chen
next prev parent reply other threads:[~2020-06-30 1:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 20:18 [PATCH v2] usb: gadget: epautoconf: claim smallest endpoints first Ruslan Bilovol
2020-06-30 1:58 ` Peter Chen [this message]
2020-07-03 10:46 ` Ruslan Bilovol
2020-07-04 10:42 ` Peter Chen
2023-02-10 20:07 ` Ruslan Bilovol
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