diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.4/0405-dmaengine-bcm2835-Avoid-splitting-periods-into-very-.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.4/0405-dmaengine-bcm2835-Avoid-splitting-periods-into-very-.patch | 56 |
1 files changed, 0 insertions, 56 deletions
diff --git a/target/linux/brcm2708/patches-4.4/0405-dmaengine-bcm2835-Avoid-splitting-periods-into-very-.patch b/target/linux/brcm2708/patches-4.4/0405-dmaengine-bcm2835-Avoid-splitting-periods-into-very-.patch deleted file mode 100644 index 6ee4e29c7c..0000000000 --- a/target/linux/brcm2708/patches-4.4/0405-dmaengine-bcm2835-Avoid-splitting-periods-into-very-.patch +++ /dev/null @@ -1,56 +0,0 @@ -From d9f7bbf7d6f175dc2363c027b931d36fb5e091d1 Mon Sep 17 00:00:00 2001 -From: Matthias Reichl <hias@horus.com> -Date: Wed, 8 Jun 2016 13:09:56 +0200 -Subject: [PATCH] dmaengine: bcm2835: Avoid splitting periods into very small - chunks - -The current cyclic DMA period splitting implementation can generate -very small chunks at the end of each period. For example a 65536 byte -period will be split into a 65532 byte chunk and a 4 byte chunk on -the "lite" DMA channels. - -This increases pressure on the RAM controller as the DMA controller -needs to fetch two control blocks from RAM in quick succession and -could potentially cause latency issues if the RAM is tied up by other -devices. - -We can easily avoid these situations by distributing the remaining -length evenly between the last-but-one and the last chunk, making -sure that split chunks will be at least half the maximum length the -DMA controller can handle. - -This patch checks if the last chunk would be less than half of -the maximum DMA length and if yes distributes the max len+4...max_len*1.5 -bytes evenly between the last 2 chunks. This results in chunk sizes -between max_len/2 and max_len*0.75 bytes. - -Signed-off-by: Matthias Reichl <hias@horus.com> -Signed-off-by: Martin Sperl <kernel@martin.sperl.org> -Tested-by: Clive Messer <clive.messer@digitaldreamtime.co.uk> ---- - drivers/dma/bcm2835-dma.c | 14 ++++++++++++++ - 1 file changed, 14 insertions(+) - ---- a/drivers/dma/bcm2835-dma.c -+++ b/drivers/dma/bcm2835-dma.c -@@ -253,6 +253,20 @@ static void bcm2835_dma_create_cb_set_le - - /* have we filled in period_length yet? */ - if (*total_len + control_block->length < period_len) { -+ /* -+ * If the next control block is the last in the period -+ * and it's length would be less than half of max_len -+ * change it so that both control blocks are (almost) -+ * equally long. This avoids generating very short -+ * control blocks (worst case would be 4 bytes) which -+ * might be problematic. We also have to make sure the -+ * new length is a multiple of 4 bytes. -+ */ -+ if (*total_len + control_block->length + max_len / 2 > -+ period_len) { -+ control_block->length = -+ DIV_ROUND_UP(period_len - *total_len, 8) * 4; -+ } - /* update number of bytes in this period so far */ - *total_len += control_block->length; - return; |