The legacy sdma driver has below limitations or drawbacks:
1. Hardcode the max BDs number as "PAGE_SIZE / sizeof(*)", and alloc
one page size for one channel regardless of only few BDs needed
most time. But in few cases, the max PAGE_SIZE maybe not enough.
2. One SDMA channel can't stop immediatley once channel disabled which
means SDMA interrupt may come in after this channel terminated.There
are some patches for this corner case such as commit "2746e2c389f9",
but not cover non-cyclic.
The common virt-dma overcomes the above limitations. It can alloc bd
dynamically and free bd once this tx transfer done. No memory wasted or
maximum limititation here, only depends on how many memory can be requested
from kernel. For No.2, such issue can be workaround by checking if there
is available descript("sdmac->desc") now once the unwanted interrupt
coming. At last the common virt-dma is easier for sdma driver maintain.
Change from v2:
1. include Sascha's patch to make the main patch easier to review.
Thanks Sacha.
2. remove useless 'desc'/'chan' in struct sdma_channe.
Change from v1:
1. split v1 patch into 5 patches.
2. remove some unnecessary condition check.
3. remove unnecessary 'pending' list.
Robin Gong (5):
dmaengine: imx-sdma: add virt-dma support
Revert "dmaengine: imx-sdma: fix pagefault when channel is disabled
during interrupt"
dmaengine: imx-sdma: remove usless lock
dmaengine: imx-sdma: remove the maximum limation for bd numbers
dmaengine: imx-sdma: add sdma_transfer_init to decrease code overlap
drivers/dma/Kconfig | 1 +
drivers/dma/imx-sdma.c | 392 ++++++++++++++++++++++++++++---------------------
2 files changed, 227 insertions(+), 166 deletions(-)
--
2.7.4
Robin Gong (5):
dmaengine: imx-sdma: add virt-dma support
Revert "dmaengine: imx-sdma: fix pagefault when channel is disabled
during interrupt"
dmaengine: imx-sdma: remove usless lock
dmaengine: imx-sdma: remove the maximum limation for bd numbers
dmaengine: imx-sdma: add sdma_transfer_init to decrease code overlap
Sascha Hauer (1):
dmaengine: imx-sdma: factor out a struct sdma_desc from struct
sdma_channel
drivers/dma/Kconfig | 1 +
drivers/dma/imx-sdma.c | 391 ++++++++++++++++++++++++++++---------------------
2 files changed, 226 insertions(+), 166 deletions(-)
--
2.7.4
