From: Peter Chen <peter.chen@nxp.com>
To: Felipe Balbi <balbi@kernel.org>
Cc: "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
dl-linux-imx <linux-imx@nxp.com>,
"pawell@cadence.com" <pawell@cadence.com>,
"rogerq@ti.com" <rogerq@ti.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
Jun Li <jun.li@nxp.com>
Subject: Re: [PATCH 8/8] usb: cdns3: gadget: enlarge the TRB ring length
Date: Tue, 8 Sep 2020 09:18:06 +0000 [thread overview]
Message-ID: <20200908091738.GC18578@b29397-desktop> (raw)
In-Reply-To: <871rjcn5hb.fsf@kernel.org>
On 20-09-08 09:32:32, Felipe Balbi wrote:
>
> Hi,
>
> Peter Chen <peter.chen@nxp.com> writes:
> > At Android ADB and MTP use case, it uses f_fs which supports scatter list,
> > it means one request may need several TRBs for it. Besides, TRB consumes
> > very fast compared to TRB has prepared for above use case, so we need to
> > enlarge the TRB ring length to avoid "no free TRB error".
>
> can you give a little more detail here?
I will.
> How many sg entries do you get with ADB? What's the size of each TRB?
I remembered it is about 120 requests for ADB and MTP use case, 16KB for
each sg entry, so four TRBs (4KB/TRB) per sg entry at worst case.
> How many memory does 600 TRBs
> actually amount to? How many segments are you using per endpoint?
>
Each TRB consumes 3 * 32 bits = 12 bytes, 600 TRB consumes 7200 bytes.
One segment for each endpoint, one segment includes 600 TRBs.
--
Thanks,
Peter Chen
next prev parent reply other threads:[~2020-09-08 9:18 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 8:44 [PATCH 0/8] usb: cdns3: improve the sg use case Peter Chen
2020-09-01 8:44 ` [PATCH 1/8] usb: cdns3: gadget: using correct sg operations Peter Chen
2020-09-08 6:19 ` Felipe Balbi
2020-09-08 7:11 ` Peter Chen
2020-09-01 8:44 ` [PATCH 2/8] usb: cdns3: gadget: improve the dump TRB operation at cdns3_ep_run_transfer Peter Chen
2020-09-08 6:19 ` Felipe Balbi
2020-09-08 7:11 ` Peter Chen
2020-09-01 8:44 ` [PATCH 3/8] usb: cdns3: gadget: calculate TDL correctly Peter Chen
2020-09-08 6:21 ` Felipe Balbi
2020-09-08 7:15 ` Peter Chen
2020-09-01 8:44 ` [PATCH 4/8] usb: cdns3: gadget: add CHAIN and ISP bit for sg list use case Peter Chen
2020-09-08 6:22 ` Felipe Balbi
2020-09-08 7:21 ` Peter Chen
2020-09-08 7:43 ` Felipe Balbi
2020-09-01 8:44 ` [PATCH 5/8] usb: cdns3: gadget: handle sg list use case at completion correctly Peter Chen
2020-09-08 6:25 ` Felipe Balbi
2020-09-08 8:34 ` Peter Chen
2020-09-10 8:37 ` Peter Chen
2020-09-01 8:44 ` [PATCH 6/8] usb: cdns3: gadget: need to handle sg case for WA2 case Peter Chen
2020-09-08 6:29 ` Felipe Balbi
2020-09-08 9:07 ` Peter Chen
2020-09-01 8:44 ` [PATCH 7/8] usb: cdns3: gadget: sg_support is only for DEV_VER_V2 or above Peter Chen
2020-09-08 6:30 ` Felipe Balbi
2020-09-08 9:08 ` Peter Chen
2020-09-01 8:44 ` [PATCH 8/8] usb: cdns3: gadget: enlarge the TRB ring length Peter Chen
2020-09-08 6:32 ` Felipe Balbi
2020-09-08 9:18 ` Peter Chen [this message]
2020-09-08 9:30 ` Felipe Balbi
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