Commit 00b5359b authored by Chen-Yu Tsai's avatar Chen-Yu Tsai Committed by Mauro Carvalho Chehab
Browse files

media: hantro: jpeg: Add COM segment to JPEG header to align image scan 



The JPEG header size is not 64-bit aligned. This makes the driver
require a bounce buffer for the encoded JPEG image scan output.

Add a COM (comment) segment to the JPEG header so that the header size
is a multiple of 64 bits. This will then allow dropping the use of the
bounce buffer, and instead have the hardware write out to the capture
buffer directly.

Signed-off-by: default avatarChen-Yu Tsai <wenst@chromium.org>
Reviewed-by: default avatarEzequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@kernel.org>
parent e90410d1

drivers/staging/media/hantro/hantro_jpeg.c

+22 −1
Original line number Diff line number Diff line
@@ -6,6 +6,9 @@ 
 * Copyright (C) Jean-Francois Moine (http://moinejf.free.fr)

 * Copyright (C) 2014 Philipp Zabel, Pengutronix

 */



#include <linux/align.h>

#include <linux/build_bug.h>

#include <linux/dma-mapping.h>

#include <linux/kernel.h>

#include <linux/string.h>
@@ -140,7 +143,7 @@ static const unsigned char chroma_ac_table[] = { 
 * and we'll use fixed offsets to change the width, height

 * quantization tables, etc.

 */

static const unsigned char hantro_jpeg_header[JPEG_HEADER_SIZE] = {

static const unsigned char hantro_jpeg_header[] = {

	/* SOI */

	0xff, 0xd8,
@@ -247,11 +250,29 @@ static const unsigned char hantro_jpeg_header[JPEG_HEADER_SIZE] = { 
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,



	/* COM */

	0xff, 0xfe, 0x00, 0x03, 0x00,



	/* SOS */

	0xff, 0xda, 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02,

	0x11, 0x03, 0x11, 0x00, 0x3f, 0x00,

};



/*

 * JPEG_HEADER_SIZE is used in other parts of the driver in lieu of

 * "sizeof(hantro_jpeg_header)". The two must be equal.

 */

static_assert(sizeof(hantro_jpeg_header) == JPEG_HEADER_SIZE);



/*

 * hantro_jpeg_header is padded with a COM segment, so that the payload

 * of the SOS segment (the entropy-encoded image scan), which should

 * trail the whole header, is 8-byte aligned for the hardware to write

 * to directly.

 */

static_assert(IS_ALIGNED(sizeof(hantro_jpeg_header), 8),

	      "Hantro JPEG header size needs to be 8-byte aligned.");



static unsigned char jpeg_scale_qp(const unsigned char qp, int scale)

{

	unsigned int temp;

drivers/staging/media/hantro/hantro_jpeg.h

+1 −1
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0+ */



#define JPEG_HEADER_SIZE	619

#define JPEG_HEADER_SIZE	624

#define JPEG_QUANT_SIZE		64



struct hantro_jpeg_ctx {