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
586a2c52909d ("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: 586a2c52909d ("mtd: nand: denali: squash denali_enable_dma() helper into
caller")
Reported-by: Steffen Trumtrar <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
---
drivers/mtd/nand/raw/denali.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/mtd/nand/raw/denali.c b/drivers/mtd/nand/raw/denali.c
index 67b2065..b864b93 100644
--- a/drivers/mtd/nand/raw/denali.c
+++ b/drivers/mtd/nand/raw/denali.c
@@ -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);
--
2.7.4
