media: vimc: Add support for contiguous DMA buffers

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.

[hverkuil: add missing 'select VIDEOBUF2_DMA_CONFIG' to Kconfig]
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/admin-guide/media/vimc.rst

@@ -76,3 +76,16 @@ vimc-capture:
 
 	* 1 Pad sink
 	* 1 Pad source
+
+Module options
+--------------
+
+Vimc has a module parameter to configure the driver.
+
+* ``allocator=<unsigned int>``
+
+	memory allocator selection, default is 0. It specifies the way buffers
+	will be allocated.
+
+		- 0: vmalloc
+		- 1: dma-contig

drivers/media/test-drivers/vimc/Kconfig

@@ -7,6 +7,7 @@ config VIDEO_VIMC
 	select MEDIA_CONTROLLER
 	select VIDEO_V4L2_SUBDEV_API
 	select VIDEOBUF2_VMALLOC
+	select VIDEOBUF2_DMA_CONTIG
 	select VIDEO_V4L2_TPG
 	help
 	  Skeleton driver for Virtual Media Controller

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;
+	if (vimc_allocator == VIMC_ALLOCATOR_VMALLOC)
+		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 == VIMC_ALLOCATOR_DMA_CONTIG
+		   ? &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) {

drivers/media/test-drivers/vimc/vimc-common.h

@@ -35,6 +35,13 @@
 
 #define VIMC_PIX_FMT_MAX_CODES 8
 
+extern unsigned int vimc_allocator;
+
+enum vimc_allocator_type {
+	VIMC_ALLOCATOR_VMALLOC = 0,
+	VIMC_ALLOCATOR_DMA_CONTIG = 1,
+};
+
 /**
  * vimc_colorimetry_clamp - Adjust colorimetry parameters
  *

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");
+
 #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 == VIMC_ALLOCATOR_DMA_CONTIG)
+		dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+
 	vimc = kzalloc(sizeof(*vimc), GFP_KERNEL);
 	if (!vimc)
 		return -ENOMEM;