From: Hui Fang <hui.fang@nxp.com>
To: Tomasz Figa <tfiga@chromium.org>
Cc: Anle Pan <anle.pan@nxp.com>,
"m.szyprowski@samsung.com" <m.szyprowski@samsung.com>,
"mchehab@kernel.org" <mchehab@kernel.org>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jindong Yue <jindong.yue@nxp.com>,
Xuegang Liu <xuegang.liu@nxp.com>
Subject: RE: [EXT] Re: [PATCH] media: videobuf2-dma-sg: limit the sg segment size
Date: Wed, 6 Sep 2023 08:16:29 +0000 [thread overview]
Message-ID: <DB9PR04MB9284A0CDB1FC7CAADE0A394F87EFA@DB9PR04MB9284.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <CAAFQd5BGJX7=Z1ukFRq_ktaQ0d7FbvV-ob5gs8hfGaNHUXPTww@mail.gmail.com>
On Wed, Sep 5, 2023 at 12:44 AM Tomasz Figa <tfiga@chromium.org> wrote:
>
> I see. I guess the mapping is done by the USB gadget controller driver? Could
> you point us to the exact driver that's used?
>
> Just to clarify, swiotlb should only be needed in the very extreme fallback case,
> because of the performance impact of the memory copy back and forth. The
> right approach would depend on the DMA capabilities of your device, though.
[ 138.493943][ T2104] Call trace:
[ 138.497090][ T2104] vb2_dma_sg_alloc+0x2ec/0x2fc
[ 138.501808][ T2104] __vb2_queue_alloc+0x224/0x724
[ 138.506608][ T2104] vb2_core_reqbufs+0x374/0x528
[ 138.511320][ T2104] vb2_reqbufs+0xe0/0xf4
[ 138.515428][ T2104] uvcg_alloc_buffers+0x18/0x34
[ 138.520159][ T2104] uvc_v4l2_reqbufs+0x38/0x54
[ 138.524703][ T2104] v4l_reqbufs+0x68/0x80
[ 138.528820][ T2104] __video_do_ioctl+0x370/0x4dc
[ 138.533535][ T2104] video_usercopy+0x43c/0xb38
[ 138.538076][ T2104] video_ioctl2+0x18/0x28
[ 138.542272][ T2104] v4l2_ioctl+0x6c/0x84
[ 138.546291][ T2104] __arm64_sys_ioctl+0xa8/0xe4
[ 138.550928][ T2104] invoke_syscall+0x58/0x114
[ 138.555389][ T2104] el0_svc_common+0x88/0xfc
[ 138.559755][ T2104] do_el0_svc+0x2c/0xb8
[ 138.563776][ T2104] el0_svc+0x2c/0xa4
[ 138.567544][ T2104] el0t_64_sync_handler+0x68/0xb4
[ 138.572434][ T2104] el0t_64_sync+0x1a4/0x1a8
[ 138.576803][ T2104] Code: 17ffffcb 928002b3 d4210000 17ffffc8 (d4210000)
[ 138.583598][ T2104] ---[ end trace 0000000000000000 ]---
Also, below should explain why vb2_dma_sg_alloc is used.
We tested on 8mp with use dwc3 controller.
In drivers/usb/dwc3/gadget.c:
dwc->gadget->sg_supported = true;
In drivers/usb/gadget/function/uvc_queue.c
if (cdev->gadget->sg_supported) {
queue->queue.mem_ops = &vb2_dma_sg_memops;
queue->use_sg = 1;
} else {
queue->queue.mem_ops = &vb2_vmalloc_memops;
}
BRs,
Fang Hui
next prev parent reply other threads:[~2023-09-06 8:16 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-28 7:54 [PATCH] media: videobuf2-dma-sg: limit the sg segment size Anle Pan
2023-08-29 10:03 ` Tomasz Figa
2023-08-29 11:14 ` Robin Murphy
2023-08-29 15:04 ` Christoph Hellwig
2023-08-30 3:47 ` Tomasz Figa
2023-08-30 14:33 ` Christoph Hellwig
2023-08-30 16:43 ` Jason Gunthorpe
2023-08-31 12:35 ` Christoph Hellwig
2023-08-31 15:32 ` Jason Gunthorpe
2023-09-01 6:10 ` Christoph Hellwig
2023-09-01 14:26 ` Jason Gunthorpe
[not found] ` <DB9PR04MB92841D8BC1122D5A4210F78987E6A@DB9PR04MB9284.eurprd04.prod.outlook.com>
2023-08-30 13:41 ` [EXT] " Robin Murphy
2023-08-30 3:59 ` Tomasz Figa
2023-09-06 8:52 ` Hans Verkuil
2023-09-06 9:26 ` Tomasz Figa
2023-09-06 9:43 ` Hans Verkuil
2023-08-30 8:50 ` Hui Fang
2023-08-30 9:28 ` Tomasz Figa
2023-09-04 7:10 ` [EXT] " Hui Fang
2023-09-05 3:43 ` Tomasz Figa
2023-09-06 8:16 ` Hui Fang [this message]
2023-09-06 9:28 ` Tomasz Figa
2023-09-11 6:13 ` Hui Fang
2023-09-12 2:22 ` Tomasz Figa
2023-09-12 7:01 ` Hui Fang
2023-09-12 7:10 ` Tomasz Figa
2023-09-12 7:43 ` Hui Fang
2023-09-12 7:51 ` Tomasz Figa
2023-09-13 9:13 ` Hui Fang
2023-09-13 9:44 ` Tomasz Figa
2023-09-13 13:16 ` Hui Fang
2023-09-18 2:28 ` Hui Fang
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