On Mon, Apr 20, 2020 at 7:31 PM Bin Meng bmeng.cn@gmail.com wrote:
Hi Jagan,
On Mon, Apr 20, 2020 at 8:52 PM Jagan Teki jagan@amarulasolutions.com wrote:
For historical reasons the existing logic of filling tx fifo
What historical reasons?
No real idea, seems like exciting logic is developed to make mmc_spi workable.
with data, rx fifo with NULL for tx transfer and filling rx fifo with data, tx fifo with NULL for rx transfer is not clear enough to support the Quad Page Program.
SiFive SPI controllers have specific sets of watermark registers and SPI I/O directions bits in order to program SPI controllers clear enough to support all sets of operating modes.
Here is the exact programing sequence that would follow on this patch and tested via SPI-NOR and MMC_SPI.
- set the frame format proto, endian
- set the frame format dir, set it for tx and clear it for rx
- TX transfer: fill tx fifo with data. wait for TX watermark bit to clear.
- TX transfer:
RX transfer ?
Thanks, my bad.
fill tx fifo with 0xff.
rx fifo ?
No it is rx fifo in order to read the rx fifo we need to pass 0xff to tx fifo, typical SPI protocol.
Jagan.