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mtd: rawnand: denali: fix a race condition when DMA is kicked

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I thought the read-back of the DMA_ENABLE register was unnecessary
(at least it is working on my boards), then deleted it in commit
586a2c5290 ("mtd: nand: denali: squash denali_enable_dma() helper
into caller").  Sorry, I was wrong - it caused a timing issue on
Cyclone5 SoCFPGAs.

Revive the register read-back, commenting why this is necessary.

Fixes: 586a2c5290 ("mtd: nand: denali: squash denali_enable_dma() helper into caller")
Cc: <[email protected]>
Reported-by: Steffen Trumtrar <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Miquel Raynal <[email protected]>
Signed-off-by: Boris Brezillon <[email protected]>
This commit is contained in:
Masahiro Yamada 2018-09-13 14:58:49 +09:00 • committed by Boris Brezillon
commit cf51e4b9c3
1 changed files with 6 additions and 0 deletions
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6
drivers/mtd/nand/raw/denali.c
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@ -596,6 +596,12 @@ static int denali_dma_xfer(struct denali_nand_info *denali, void *buf,
}
iowrite32(DMA_ENABLE__FLAG, denali->reg + DMA_ENABLE);
/*
* The ->setup_dma() hook kicks DMA by using the data/command
* interface, which belongs to a different AXI port from the
* register interface. Read back the register to avoid a race.
*/
ioread32(denali->reg + DMA_ENABLE);
denali_reset_irq(denali);
denali->setup_dma(denali, dma_addr, page, write);