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: Chen-Yu Tsai <wenst@xxxxxxxxxxxx> --- drivers/staging/media/hantro/hantro_jpeg.c | 23 +++++++++++++++++++++- drivers/staging/media/hantro/hantro_jpeg.h | 2 +- 2 files changed, 23 insertions(+), 2 deletions(-) diff --git a/drivers/staging/media/hantro/hantro_jpeg.c b/drivers/staging/media/hantro/hantro_jpeg.c index 7d4018bd6876..e63eeef3952d 100644 --- a/drivers/staging/media/hantro/hantro_jpeg.c +++ b/drivers/staging/media/hantro/hantro_jpeg.c @@ -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; diff --git a/drivers/staging/media/hantro/hantro_jpeg.h b/drivers/staging/media/hantro/hantro_jpeg.h index f33c492134e4..0b49d0b82caa 100644 --- a/drivers/staging/media/hantro/hantro_jpeg.h +++ b/drivers/staging/media/hantro/hantro_jpeg.h @@ -1,6 +1,6 @@ /* 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 { -- 2.34.1.575.g55b058a8bb-goog
