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From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Cc: linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	Helen Koike <helen.koike@collabora.com>,
	Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH] media: vimc: Add support for contiguous DMA buffers
Date: Fri, 30 Jul 2021 17:15:34 +0300	[thread overview]
Message-ID: <YQQJhjOtPb10+olI@pendragon.ideasonboard.com> (raw)
In-Reply-To: <69e4b3fe-5e31-840a-9ea6-a3050f9a6a20@collabora.com>

Hi Dafna,

On Fri, Jul 30, 2021 at 04:08:11PM +0200, Dafna Hirschfeld wrote:
> On 30.07.21 15:11, Laurent Pinchart wrote:
> > On Fri, Jul 30, 2021 at 02:35:20PM +0200, Dafna Hirschfeld wrote:
> >> On 30.07.21 02:19, Laurent Pinchart wrote:
> >>> The vimc driver is used for testing purpose, and some test use cases
> >>> involve sharing buffers with a consumer device. Consumers often require
> >>> DMA contiguous memory, which vimc doesn't currently support. This leads
> >>> in the best case to usage of bounce buffers, which is very slow, and in
> >>> the worst case in a complete failure.
> >>>
> >>> Add support for the dma-contig allocator in vimc to support those use
> >>> cases properly. The allocator is selected through a new "allocator"
> >>> module parameter, which defaults to vmalloc.
> >>>
> >>> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> >>> ---
> >>>    drivers/media/test-drivers/vimc/vimc-capture.c |  9 +++++++--
> >>>    drivers/media/test-drivers/vimc/vimc-common.h  |  2 ++
> >>>    drivers/media/test-drivers/vimc/vimc-core.c    | 10 ++++++++++
> >>>    3 files changed, 19 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/media/test-drivers/vimc/vimc-capture.c b/drivers/media/test-drivers/vimc/vimc-capture.c
> >>> index 5e9fd902cd37..92b69a6529fb 100644
> >>> --- a/drivers/media/test-drivers/vimc/vimc-capture.c
> >>> +++ b/drivers/media/test-drivers/vimc/vimc-capture.c
> >>> @@ -7,6 +7,7 @@
> >>>    
> >>>    #include <media/v4l2-ioctl.h>
> >>>    #include <media/videobuf2-core.h>
> >>> +#include <media/videobuf2-dma-contig.h>
> >>>    #include <media/videobuf2-vmalloc.h>
> >>>    
> >>>    #include "vimc-common.h"
> >>> @@ -423,14 +424,18 @@ static struct vimc_ent_device *vimc_cap_add(struct vimc_device *vimc,
> >>>    	/* Initialize the vb2 queue */
> >>>    	q = &vcap->queue;
> >>>    	q->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> >>> -	q->io_modes = VB2_MMAP | VB2_DMABUF | VB2_USERPTR;
> >>> +	q->io_modes = VB2_MMAP | VB2_DMABUF;
> >>
> >> maybe to be on the safe side VB2_DMABUF should be set only if vimc_allocator==1 ?
> > 
> > Why so ? vb2-vmalloc can import dma-bufs.
> 
> oh, I meant that exporting should not be supported.
> I see that vimc set ".vidioc_expbuf = vb2_ioctl_expbuf", maybe remove that if allocator is vmalloc?

If the importer support non-contiguous buffers, vb2-vmalloc can be used
as an exporter. I've successfully used this to test sharing buffers
between vimc in vmalloc mode and the R-Car H3 display driver with an
IOMMU.

> >>> +	if (vimc_allocator != 1)
> >>
> >> maybe define a macro instead of `1` ?
> > 
> > Good idea.
> > 
> >>> +		q->io_modes |= VB2_USERPTR;
> >>>    	q->drv_priv = vcap;
> >>>    	q->buf_struct_size = sizeof(struct vimc_cap_buffer);
> >>>    	q->ops = &vimc_cap_qops;
> >>> -	q->mem_ops = &vb2_vmalloc_memops;
> >>> +	q->mem_ops = vimc_allocator == 1
> >>> +		   ? &vb2_dma_contig_memops : &vb2_vmalloc_memops;
> >>>    	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> >>>    	q->min_buffers_needed = 2;
> >>>    	q->lock = &vcap->lock;
> >>> +	q->dev = v4l2_dev->dev;
> >>>    
> >>>    	ret = vb2_queue_init(q);
> >>>    	if (ret) {
> >>> diff --git a/drivers/media/test-drivers/vimc/vimc-common.h b/drivers/media/test-drivers/vimc/vimc-common.h
> >>> index a289434e75ba..b77939123501 100644
> >>> --- a/drivers/media/test-drivers/vimc/vimc-common.h
> >>> +++ b/drivers/media/test-drivers/vimc/vimc-common.h
> >>> @@ -35,6 +35,8 @@
> >>>    
> >>>    #define VIMC_PIX_FMT_MAX_CODES 8
> >>>    
> >>> +extern unsigned int vimc_allocator;
> >>> +
> >>>    /**
> >>>     * vimc_colorimetry_clamp - Adjust colorimetry parameters
> >>>     *
> >>> diff --git a/drivers/media/test-drivers/vimc/vimc-core.c b/drivers/media/test-drivers/vimc/vimc-core.c
> >>> index 4b0ae6f51d76..7badcecb7aed 100644
> >>> --- a/drivers/media/test-drivers/vimc/vimc-core.c
> >>> +++ b/drivers/media/test-drivers/vimc/vimc-core.c
> >>> @@ -5,6 +5,7 @@
> >>>     * Copyright (C) 2015-2017 Helen Koike <helen.fornazier@gmail.com>
> >>>     */
> >>>    
> >>> +#include <linux/dma-mapping.h>
> >>>    #include <linux/font.h>
> >>>    #include <linux/init.h>
> >>>    #include <linux/module.h>
> >>> @@ -15,6 +16,12 @@
> >>>    
> >>>    #include "vimc-common.h"
> >>>    
> >>> +unsigned int vimc_allocator;
> >>> +module_param_named(allocator, vimc_allocator, uint, 0444);
> >>> +MODULE_PARM_DESC(allocator, " memory allocator selection, default is 0.\n"
> >>> +			     "\t\t    0 == vmalloc\n"
> >>> +			     "\t\t    1 == dma-contig");
> >>> +
> >>
> >> There is a section 'Module options' in vimc.rst. So a doc should be added there.
> > 
> > OK, I'll update that.
> > 
> >>>    #define VIMC_MDEV_MODEL_NAME "VIMC MDEV"
> >>>    
> >>>    #define VIMC_ENT_LINK(src, srcpad, sink, sinkpad, link_flags) {	\
> >>> @@ -278,6 +285,9 @@ static int vimc_probe(struct platform_device *pdev)
> >>>    
> >>>    	tpg_set_font(font->data);
> >>>    
> >>> +	if (vimc_allocator == 1)
> >>> +		dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> >>> +
> >>>    	vimc = kzalloc(sizeof(*vimc), GFP_KERNEL);
> >>>    	if (!vimc)
> >>>    		return -ENOMEM;
> >>>

-- 
Regards,

Laurent Pinchart

  reply	other threads:[~2021-07-30 14:15 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30  0:19 Laurent Pinchart
2021-07-30 12:35 ` Dafna Hirschfeld
2021-07-30 13:11   ` Laurent Pinchart
2021-07-30 14:08     ` Dafna Hirschfeld
2021-07-30 14:15       ` Laurent Pinchart [this message]
2021-07-30 15:59         ` Nicolas Dufresne
2021-07-30 16:56           ` Laurent Pinchart
2021-07-30 15:56     ` Nicolas Dufresne
2021-07-30 16:13   ` Ezequiel Garcia
2021-07-30 16:50     ` Laurent Pinchart

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