[PATCH 1/2] video: udlfb: Fix unaligned access
From: Ladislav Michl <hidden>
Date: 2018-02-06 20:08:38
Driver generates lots of alignment trap exceptions on ARM. Fix that by replacing typecasting of odd addresses with byte shifting and remove uneccessary typecasting. Signed-off-by: Ladislav Michl <redacted> --- Here's what happens on at91sam9g20 few minutes after boot: $ cat /proc/cpu/alignment User: 0 System: 10747836 (dlfb_render_hline+0x22c/0x2f0 [udlfb]) Skipped: 0 Half: 10747971 Word: 159 DWord: 0 Multi: 0 Each hline transfer causes dozens alignment exceptions and few are in dlfb_parse_vendor_descriptor function. drivers/video/fbdev/udlfb.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
index 452a4207ac1b..45081297efa5 100644
--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c@@ -441,9 +441,9 @@ static void dlfb_compress_hline( *cmd++ = 0xAF; *cmd++ = 0x6B; - *cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF); - *cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF); - *cmd++ = (uint8_t) ((dev_addr) & 0xFF); + *cmd++ = dev_addr >> 16; + *cmd++ = dev_addr >> 8; + *cmd++ = dev_addr; cmd_pixels_count_byte = cmd++; /* we'll know this later */ cmd_pixel_start = pixel;
@@ -460,8 +460,8 @@ static void dlfb_compress_hline( while (pixel < cmd_pixel_end) { const uint16_t * const repeating_pixel = pixel; - *(uint16_t *)cmd = cpu_to_be16p(pixel); - cmd += 2; + *cmd++ = *pixel >> 8; + *cmd++ = *pixel; pixel++; if (unlikely((pixel < cmd_pixel_end) &&
@@ -1531,15 +1531,16 @@ static int dlfb_parse_vendor_descriptor(struct dlfb_data *dlfb, u8 length; u16 key; - key = le16_to_cpu(*((u16 *) desc)); - desc += sizeof(u16); - length = *desc; - desc++; + key = *desc++; + key |= (u16)*desc++ << 8; + length = *desc++; switch (key) { case 0x0200: { /* max_area */ - u32 max_area; - max_area = le32_to_cpu(*((u32 *)desc)); + u32 max_area = *desc++; + max_area |= (u32)*desc++ << 8; + max_area |= (u32)*desc++ << 16; + max_area |= (u32)*desc++ << 24; dev_warn(&intf->dev, "DL chip limited to %d pixel modes\n", max_area);
--
2.16.1