On Thu, 13 Sep 2018 14:58:49 +0900
Masahiro Yamada <yamada.masah...@socionext.com> wrote:
> 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 <s.trumt...@pengutronix.de>
> Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com>
Queued to master.
Thanks,
Boris
> ---
>
> 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);
