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| H A D | spi-rockchip.c | diff 47300728fb213486a830565d2af49da967c9d16a Fri Apr 12 12:53:20 CEST 2019 Emil Renner Berthing <kernel@esmil.dk> spi: rockchip: turn down tx dma bursts
This fixes tx and bi-directional dma transfers on rk3399-gru-kevin.
It seems the SPI fifo must have room for 2 bursts when the dma_tx_req
signal is generated or it might skip some words. This in turn makes
the rx dma channel never complete for bi-directional transfers.
Fix it by setting tx burst length to fifo_len / 4 and the dma
watermark to fifo_len / 2.
However the rk3399 TRM says (sic):
"DMAC support incrementing-address burst and fixed-address burst. But in
the case of access SPI and UART at byte or halfword size, DMAC only
support fixed-address burst and the address must be aligned to word."
So this relies on fifo_len being a multiple of 16 such that the
burst length (= fifo_len / 4) is a multiple of 4 and the addresses
will be word-aligned.
Fixes: dcfc861d24ec ("spi: rockchip: adjust dma watermark and burstlen")
Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>
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