Because DMA2 may be in use by other peripherals, eg SPI1.
On PYBD-SF6 it's possible to trigger a bug in the existing code by turning
on WLAN and connecting to an AP, pinging the IP address from a PC and
running the following code on the PYBD:
def spi_test(s):
while 1:
s.write('test')
s.read(4)
spi_test(machine.SPI(1,100000000))
This will eventually fail with `OSError: [Errno 110] ETIMEDOUT` because
DMA2 was turned off by the CYW43 driver during the SPI1 transfer.
This commit fixes the bug by removing the code that explicitly disables
DMA2. Instead DMA2 will be automatically disabled after an inactivity
timeout, see commit a96afae90f
Signed-off-by: Damien George <damien@micropython.org>
The DMA driver will turn off DMA if it hasn't been used for an amount of
time (to save power). The SDIO driver for cyw43 WLAN was not informing the
DMA driver that it was using DMA and there was a chance that the DMA would
turn off in the middle of an SDIO DMA transfer. The symptoms of this would
be printing of SDIO error messages and a failure to communicate with the
cyw43 WLAN module.
This commit fixes this issue by changing the SDIO driver to use the
dma_nohal_XXX API to initialise and start the DMA.
Signed-off-by: Damien George <damien@micropython.org>
This can now be selected by setting MICROPY_HW_SDIO_SDMMC, which defaults
to 1, ie SDMMC1. The pins can also be selected and default to the standard
C8/C9/C10/C11/C12/D2.
