Message-ID: <4a02833e-67a6-ec4f-d2f6-e0368412eca8@xs4all.nl>
Date:   Wed, 17 Oct 2018 12:41:09 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Eddie James <eajames@...ux.ibm.com>, linux-kernel@...r.kernel.org
Cc:     mark.rutland@....com, devicetree@...r.kernel.org,
        linux-aspeed@...ts.ozlabs.org, andrew@...id.au,
        openbmc@...ts.ozlabs.org, robh+dt@...nel.org, mchehab@...nel.org,
        linux-media@...r.kernel.org, joel@....id.au
Subject: Re: [PATCH v4 2/2] media: platform: Add Aspeed Video Engine driver

On 10/05/2018 09:57 PM, Eddie James wrote:
> The Video Engine (VE) embedded in the Aspeed AST2400 and AST2500 SOCs
> can capture and compress video data from digital or analog sources. With
> the Aspeed chip acting a service processor, the Video Engine can capture
> the host processor graphics output.
> 
> Add a V4L2 driver to capture video data and compress it to JPEG images.
> Make the video frames available through the V4L2 streaming interface.
> 
> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> ---
>  MAINTAINERS                           |    8 +
>  drivers/media/platform/Kconfig        |    8 +
>  drivers/media/platform/Makefile       |    1 +
>  drivers/media/platform/aspeed-video.c | 1674 +++++++++++++++++++++++++++++++++
>  4 files changed, 1691 insertions(+)
>  create mode 100644 drivers/media/platform/aspeed-video.c
> 

<snip>

> +static void aspeed_video_check_polarity(struct aspeed_video *video)
> +{
> +	int i;
> +	int hsync_counter = 0;
> +	int vsync_counter = 0;
> +	u32 sts;
> +
> +	for (i = 0; i < NUM_POLARITY_CHECKS; ++i) {
> +		sts = aspeed_video_read(video, VE_MODE_DETECT_STATUS);
> +		if (sts & VE_MODE_DETECT_STATUS_VSYNC)
> +			vsync_counter--;
> +		else
> +			vsync_counter++;
> +
> +		if (sts & VE_MODE_DETECT_STATUS_HSYNC)
> +			hsync_counter--;
> +		else
> +			hsync_counter++;
> +	}
> +
> +	if (hsync_counter < 0 || vsync_counter < 0) {
> +		u32 ctrl;
> +
> +		if (hsync_counter < 0)
> +			ctrl = VE_CTRL_HSYNC_POL;
> +		else
> +			video->timings.polarities |= V4L2_DV_HSYNC_POS_POL;
> +
> +		if (vsync_counter < 0)
> +			ctrl = VE_CTRL_VSYNC_POL;
> +		else
> +			video->timings.polarities |= V4L2_DV_VSYNC_POS_POL;
> +
> +		aspeed_video_update(video, VE_CTRL, 0, ctrl);
> +	}
> +}
> +
> +static bool aspeed_video_alloc_buf(struct aspeed_video *video,
> +				   struct aspeed_video_addr *addr,
> +				   unsigned int size)
> +{
> +	addr->virt = dma_alloc_coherent(video->dev, size, &addr->dma,
> +					GFP_KERNEL);
> +	if (!addr->virt)
> +		return false;
> +
> +	addr->size = size;
> +	return true;
> +}
> +
> +static void aspeed_video_free_buf(struct aspeed_video *video,
> +				  struct aspeed_video_addr *addr)
> +{
> +	dma_free_coherent(video->dev, addr->size, addr->virt, addr->dma);
> +	addr->size = 0;
> +	addr->dma = 0ULL;
> +	addr->virt = NULL;
> +}
> +
> +/*
> + * Get the minimum HW-supported compression buffer size for the frame size.
> + * Assume worst-case JPEG compression size is 1/8 raw size. This should be
> + * plenty even for maximum quality; any worse and the engine will simply return
> + * incomplete JPEGs.
> + */
> +static void aspeed_video_calc_compressed_size(struct aspeed_video *video)
> +{
> +	int i, j;
> +	u32 compression_buffer_size_reg = 0;
> +	unsigned int size;
> +	const unsigned int num_compression_packets = 4;
> +	const unsigned int compression_packet_size = 1024;
> +	const unsigned int max_compressed_size =
> +		video->width * video->height / 2;	/* 4 Bpp / 8 */
> +
> +	video->max_compressed_size = UINT_MAX;
> +
> +	for (i = 0; i < 6; ++i) {
> +		for (j = 0; j < 8; ++j) {
> +			size = (num_compression_packets << i) *
> +				(compression_packet_size << j);
> +			if (size < max_compressed_size)
> +				continue;
> +
> +			if (size < video->max_compressed_size) {
> +				compression_buffer_size_reg = (i << 3) | j;
> +				video->max_compressed_size = size;
> +			}
> +		}
> +	}
> +
> +	aspeed_video_write(video, VE_STREAM_BUF_SIZE,
> +			   compression_buffer_size_reg);
> +
> +	dev_dbg(video->dev, "max compressed size: %x\n",
> +		video->max_compressed_size);
> +}
> +
> +#define res_check(v) test_and_clear_bit(VIDEO_MODE_DETECT_DONE, &(v)->flags)
> +
> +static int aspeed_video_get_resolution(struct aspeed_video *video)
> +{
> +	bool invalid_resolution = true;
> +	int rc;
> +	int tries = 0;
> +	unsigned int bottom;
> +	unsigned int left;
> +	unsigned int right;
> +	unsigned int size;
> +	unsigned int top;
> +	u32 mds;
> +	u32 src_lr_edge;
> +	u32 src_tb_edge;
> +	u32 sync;
> +	struct aspeed_video_addr src;
> +
> +	if (video->srcs[1].size)
> +		aspeed_video_free_buf(video, &video->srcs[1]);
> +
> +	if (video->srcs[0].size >= VE_MAX_SRC_BUFFER_SIZE) {
> +		src = video->srcs[0];
> +	} else {
> +		if (video->srcs[0].size)
> +			aspeed_video_free_buf(video, &video->srcs[0]);
> +
> +		if (!aspeed_video_alloc_buf(video, &src,
> +					    VE_MAX_SRC_BUFFER_SIZE))
> +			goto err_mem;
> +	}
> +
> +	aspeed_video_write(video, VE_SRC0_ADDR, src.dma);
> +
> +	video->width = 0;
> +	video->height = 0;
> +
> +	do {
> +		if (tries) {
> +			set_current_state(TASK_INTERRUPTIBLE);
> +			if (schedule_timeout(INVALID_RESOLUTION_DELAY))
> +				return -EINTR;
> +		}
> +
> +		aspeed_video_start_mode_detect(video);
> +
> +		rc = wait_event_interruptible_timeout(video->wait,
> +						      res_check(video),
> +						      MODE_DETECT_TIMEOUT);
> +		if (!rc) {
> +			dev_err(video->dev, "timed out on 1st mode detect\n");
> +			aspeed_video_disable_mode_detect(video);
> +			return -ETIMEDOUT;
> +		}
> +
> +		/* Disable mode detect in order to re-trigger */
> +		aspeed_video_update(video, VE_SEQ_CTRL,
> +				    VE_SEQ_CTRL_TRIG_MODE_DET, 0);
> +
> +		aspeed_video_check_polarity(video);
> +
> +		aspeed_video_start_mode_detect(video);
> +
> +		rc = wait_event_interruptible_timeout(video->wait,
> +						      res_check(video),
> +						      MODE_DETECT_TIMEOUT);
> +		if (!rc) {
> +			dev_err(video->dev, "timed out on 2nd mode detect\n");
> +			aspeed_video_disable_mode_detect(video);
> +			return -ETIMEDOUT;
> +		}
> +
> +		src_lr_edge = aspeed_video_read(video, VE_SRC_LR_EDGE_DET);
> +		src_tb_edge = aspeed_video_read(video, VE_SRC_TB_EDGE_DET);
> +		mds = aspeed_video_read(video, VE_MODE_DETECT_STATUS);
> +		sync = aspeed_video_read(video, VE_SYNC_STATUS);
> +
> +		bottom = (src_tb_edge & VE_SRC_TB_EDGE_DET_BOT) >>
> +			VE_SRC_TB_EDGE_DET_BOT_SHF;
> +		top = src_tb_edge & VE_SRC_TB_EDGE_DET_TOP;
> +		video->timings.vfrontporch = top;
> +		video->timings.vbackporch = ((mds & VE_MODE_DETECT_V_LINES) >>
> +			VE_MODE_DETECT_V_LINES_SHF) - bottom;
> +		video->timings.vsync = (sync & VE_SYNC_STATUS_VSYNC) >>
> +			VE_SYNC_STATUS_VSYNC_SHF;
> +		if (top > bottom)
> +			continue;
> +
> +		right = (src_lr_edge & VE_SRC_LR_EDGE_DET_RT) >>
> +			VE_SRC_LR_EDGE_DET_RT_SHF;
> +		left = src_lr_edge & VE_SRC_LR_EDGE_DET_LEFT;
> +		video->timings.hfrontporch = left;
> +		video->timings.hbackporch = (mds & VE_MODE_DETECT_H_PIXELS) -
> +			right;
> +		video->timings.hsync = sync & VE_SYNC_STATUS_HSYNC;

It's a bit odd that timings.width/height isn't set here.

> +		if (left > right)
> +			continue;
> +
> +		invalid_resolution = false;
> +	} while (invalid_resolution && (tries++ < INVALID_RESOLUTION_RETRIES));
> +
> +	if (invalid_resolution) {
> +		dev_err(video->dev, "invalid resolution detected\n");
> +		return -ERANGE;
> +	}

So far, so good. You now have detected the new resolution, but...

> +
> +	video->height = (bottom - top) + 1;
> +	video->width = (right - left) + 1;
> +	size = video->height * video->width;

here and below you appear to actually switch the capture timings to the new
resolution as well.

That should only happen when s_dv_timings is called.

It is always very dangerous to automatically switch resolution since a new
resolution might mean larger buffers, and userspace has to prepare for that.

The normal sequence is:

1) the driver detects a change in resolution (or the video signal disappears
completely). It will send V4L2_EVENT_SOURCE_CHANGE to let userspace know.

2) Userspace stops streaming, frees all buffers, calls QUERY_DV_TIMINGS and,
   if valid, follows with S_DV_TIMINGS.

3) Userspace calls REQBUFS to allocate the new buffers sized for the new timings
   and starts streaming again.

That way everything remains under control of the application.

> +
> +	/* Don't use direct mode below 1024 x 768 (irqs don't fire) */
> +	if (size < DIRECT_FETCH_THRESHOLD) {
> +		aspeed_video_write(video, VE_TGS_0,
> +				   FIELD_PREP(VE_TGS_FIRST, left - 1) |
> +				   FIELD_PREP(VE_TGS_LAST, right));
> +		aspeed_video_write(video, VE_TGS_1,
> +				   FIELD_PREP(VE_TGS_FIRST, top) |
> +				   FIELD_PREP(VE_TGS_LAST, bottom + 1));
> +		aspeed_video_update(video, VE_CTRL, 0, VE_CTRL_INT_DE);
> +	} else {
> +		aspeed_video_update(video, VE_CTRL, 0, VE_CTRL_DIRECT_FETCH);
> +	}
> +
> +	aspeed_video_write(video, VE_CAP_WINDOW,
> +			   video->width << 16 | video->height);
> +	aspeed_video_write(video, VE_COMP_WINDOW,
> +			   video->width << 16 | video->height);
> +	aspeed_video_write(video, VE_SRC_SCANLINE_OFFSET, video->width * 4);
> +
> +	aspeed_video_update(video, VE_INTERRUPT_CTRL, 0,
> +			    VE_INTERRUPT_MODE_DETECT_WD);
> +	aspeed_video_update(video, VE_SEQ_CTRL, 0,
> +			    VE_SEQ_CTRL_AUTO_COMP | VE_SEQ_CTRL_EN_WATCHDOG);
> +
> +	dev_dbg(video->dev, "got resolution[%dx%d]\n", video->width,
> +		video->height);
> +
> +	size *= 4;
> +	if (size == src.size / 2) {
> +		aspeed_video_write(video, VE_SRC1_ADDR, src.dma + size);
> +		video->srcs[0] = src;
> +	} else if (size == src.size) {
> +		video->srcs[0] = src;
> +
> +		if (!aspeed_video_alloc_buf(video, &video->srcs[1], size))
> +			goto err_mem;
> +
> +		aspeed_video_write(video, VE_SRC1_ADDR, video->srcs[1].dma);
> +	} else {
> +		aspeed_video_free_buf(video, &src);
> +
> +		if (!aspeed_video_alloc_buf(video, &video->srcs[0], size))
> +			goto err_mem;
> +
> +		if (!aspeed_video_alloc_buf(video, &video->srcs[1], size))
> +			goto err_mem;
> +
> +		aspeed_video_write(video, VE_SRC0_ADDR, video->srcs[0].dma);
> +		aspeed_video_write(video, VE_SRC1_ADDR, video->srcs[1].dma);
> +	}
> +
> +	aspeed_video_calc_compressed_size(video);
> +
> +	return 0;
> +
> +err_mem:
> +	dev_err(video->dev, "failed to allocate source buffers\n");
> +
> +	if (video->srcs[0].size)
> +		aspeed_video_free_buf(video, &video->srcs[0]);
> +
> +	return -ENOMEM;
> +}

Regards,

	Hans

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