Subject: Re: [PATCH v2 1/3] media: cedrus: Fix decoding for some H264 videos

From: Paul Kocialkowski <[email-masked]>
Date: Tue, 22 Oct 2019 11:10:02 +0200

Hi,

On Tue 15 Oct 19, 19:16, Jernej Škrabec wrote:
> Please understand that I was working on this on and off for almost half a year 
> and checked many times all register values. At one point I tried libvdpau-
> sunxi which has no problem with sample video.  Still, all relevant register 
> values were the same. In a desperate attempt, I tried with HW header parsing 
> which magically solved the issue. After that, I reused values provided in 
> controls and then finally I made minimal solution as suggested in this patch. 

Okay thanks for the details.

I think I've delayed this for far too long already so I think we should get it
in without further delay.

The patch apparently no longer applies on top of media/master, but feel free
to send out a rebased series with:

Acked-by: Paul Kocialkowski <[email-masked]>

Let's leave out 2/3 though, I think I will submit a series adding the flag
as indication for the per-slice value in the uAPI and use it in cedrus.

Cheers,

Paul

> > 
> > I could try and have a look if you have an available sample for testing the
> > erroneous case!
> 
> Of course: http://jernej.libreelec.tv/videos/h264/test.mkv
> 
> > 
> > Another minor thing: do you have some idea of whether the udelay call adds
> > significant delay in the process?
> 
> I didn't notice any issue with it. Do you have any better idea? I just didn't 
> want to make empty loop and udelay is the shortest delay that is provided by 
> the kernel API.
> 
> Best regards,
> Jernej
> 
> > 
> > Cheers and thanks for the patch!
> > 
> > Paul
> > 
> > > Signed-off-by: Jernej Skrabec <[email-masked]>
> > > ---
> > > 
> > >  .../staging/media/sunxi/cedrus/cedrus_h264.c  | 30 +++++++++++++++++--
> > >  .../staging/media/sunxi/cedrus/cedrus_regs.h  |  3 ++
> > >  2 files changed, 30 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c index
> > > d6a782703c9b..bd848146eada 100644
> > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > @@ -6,6 +6,7 @@
> > > 
> > >   * Copyright (c) 2018 Bootlin
> > >   */
> > > 
> > > +#include <linux/delay.h>
> > > 
> > >  #include <linux/types.h>
> > >  
> > >  #include <media/videobuf2-dma-contig.h>
> > > 
> > > @@ -289,6 +290,28 @@ static void cedrus_write_pred_weight_table(struct
> > > cedrus_ctx *ctx,> 
> > >  	}
> > >  
> > >  }
> > > 
> > > +/*
> > > + * It turns out that using VE_H264_VLD_OFFSET to skip bits is not
> > > reliable. In + * rare cases frame is not decoded correctly. However,
> > > setting offset to 0 and + * skipping appropriate amount of bits with
> > > flush bits trigger always works. + */
> > > +static void cedrus_skip_bits(struct cedrus_dev *dev, int num)
> > > +{
> > > +	int count = 0;
> > > +
> > > +	while (count < num) {
> > > +		int tmp = min(num - count, 32);
> > > 
> > > +
> > > +		cedrus_write(dev, VE_H264_TRIGGER_TYPE,
> > > +			     VE_H264_TRIGGER_TYPE_FLUSH_BITS |
> > > +			     VE_H264_TRIGGER_TYPE_N_BITS(tmp));
> > > +		while (cedrus_read(dev, VE_H264_STATUS) & 
> VE_H264_STATUS_VLD_BUSY)
> > > +			udelay(1);
> > > +
> > > +		count += tmp;
> > > +	}
> > > +}
> > > +
> > > 
> > >  static void cedrus_set_params(struct cedrus_ctx *ctx,
> > >  
> > >  			      struct cedrus_run *run)
> > >  
> > >  {
> > > 
> > > @@ -299,12 +322,11 @@ static void cedrus_set_params(struct cedrus_ctx
> > > *ctx,
> > > 
> > >  	struct vb2_buffer *src_buf = &run->src->vb2_buf;
> > >  	struct cedrus_dev *dev = ctx->dev;
> > >  	dma_addr_t src_buf_addr;
> > > 
> > > -	u32 offset = slice->header_bit_size;
> > > -	u32 len = (slice->size * 8) - offset;
> > > +	u32 len = slice->size * 8;
> > > 
> > >  	u32 reg;
> > >  	
> > >  	cedrus_write(dev, VE_H264_VLD_LEN, len);
> > > 
> > > -	cedrus_write(dev, VE_H264_VLD_OFFSET, offset);
> > > +	cedrus_write(dev, VE_H264_VLD_OFFSET, 0);
> > > 
> > >  	src_buf_addr = vb2_dma_contig_plane_dma_addr(src_buf, 0);
> > >  	cedrus_write(dev, VE_H264_VLD_END,
> > > 
> > > @@ -323,6 +345,8 @@ static void cedrus_set_params(struct cedrus_ctx *ctx,
> > > 
> > >  	cedrus_write(dev, VE_H264_TRIGGER_TYPE,
> > >  	
> > >  		     VE_H264_TRIGGER_TYPE_INIT_SWDEC);
> > > 
> > > +	cedrus_skip_bits(dev, slice->header_bit_size);
> > > +
> > > 
> > >  	if (((pps->flags & V4L2_H264_PPS_FLAG_WEIGHTED_PRED) &&
> > >  	
> > >  	     (slice->slice_type == V4L2_H264_SLICE_TYPE_P ||
> > >  	     
> > >  	      slice->slice_type == V4L2_H264_SLICE_TYPE_SP)) ||
> > > 
> > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> > > b/drivers/staging/media/sunxi/cedrus/cedrus_regs.h index
> > > 3329f9aaf975..b52926a54025 100644
> > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_regs.h
> > > @@ -538,13 +538,16 @@
> > > 
> > >  					 
> VE_H264_CTRL_SLICE_DECODE_INT)
> > >  
> > >  #define VE_H264_TRIGGER_TYPE		0x224
> > > 
> > > +#define VE_H264_TRIGGER_TYPE_N_BITS(x)		(((x) & 0x3f) << 8)
> > > 
> > >  #define VE_H264_TRIGGER_TYPE_AVC_SLICE_DECODE	(8 << 0)
> > >  #define VE_H264_TRIGGER_TYPE_INIT_SWDEC		(7 << 0)
> > > 
> > > +#define VE_H264_TRIGGER_TYPE_FLUSH_BITS		(3 << 0)
> > > 
> > >  #define VE_H264_STATUS			0x228
> > >  #define VE_H264_STATUS_VLD_DATA_REQ_INT		
> VE_H264_CTRL_VLD_DATA_REQ_INT
> > >  #define VE_H264_STATUS_DECODE_ERR_INT		
> VE_H264_CTRL_DECODE_ERR_INT
> > >  #define VE_H264_STATUS_SLICE_DECODE_INT		
> VE_H264_CTRL_SLICE_DECODE_INT
> > > 
> > > +#define VE_H264_STATUS_VLD_BUSY			BIT(8)
> > > 
> > >  #define VE_H264_STATUS_INT_MASK			
> VE_H264_CTRL_INT_MASK
> 
> 
> 
> 
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