mtd: rawnand: sunxi: add H616 MBUS DMA support

The H616 NAND controller uses a descriptor-based internal MBUS DMA
engine instead of the direct address and count registers used by the
A23/A33 controller. Since the driver does not support these descriptors,
it currently attempts to request an external rxtx DMA channel and falls
back to PIO when none is provided.

Add a single-descriptor backend to the existing ECC page DMA paths.
Allocate the descriptor coherently, constrain data mappings to the
controller's 32-bit address range, program the H6-style data block mask,
and request an interrupt for both command and DMA completion. Keep the
existing external DMA and legacy MBUS DMA paths unchanged, and fall back
to PIO if the descriptor cannot be allocated.

With identical kernels except for this patch, running
flash_speed -d -b 1906 -c 100 /dev/mtd6 on an H616 board with 2 KiB-page
SLC NAND reported:

                         PIO          descriptor DMA
eraseblock write        3365 KiB/s       4192 KiB/s
eraseblock read         6454 KiB/s      16040 KiB/s
page write              3254 KiB/s       4021 KiB/s
page read               6419 KiB/s      15686 KiB/s

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

0 files changed, 0 insertions, 0 deletions