* [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked
@ 2018-09-13 5:58 Masahiro Yamada
2018-09-14 14:29 ` Miquel Raynal
2018-09-17 12:32 ` Boris Brezillon
0 siblings, 2 replies; 3+ messages in thread
From: Masahiro Yamada @ 2018-09-13 5:58 UTC (permalink / raw)
To: linux-mtd, Boris Brezillon, Miquel Raynal
Cc: Steffen Trumtrar, Masahiro Yamada, linux-kernel, Marek Vasut,
Brian Norris, Richard Weinberger, David Woodhouse
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.trumtrar@pengutronix.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked
2018-09-13 5:58 [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked Masahiro Yamada
@ 2018-09-14 14:29 ` Miquel Raynal
2018-09-17 12:32 ` Boris Brezillon
1 sibling, 0 replies; 3+ messages in thread
From: Miquel Raynal @ 2018-09-14 14:29 UTC (permalink / raw)
To: Masahiro Yamada
Cc: linux-mtd, Boris Brezillon, Steffen Trumtrar, linux-kernel,
Marek Vasut, Brian Norris, Richard Weinberger, David Woodhouse
Hello,
Masahiro Yamada <yamada.masahiro@socionext.com> wrote on Thu, 13 Sep
2018 14:58:49 +0900:
> 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.trumtrar@pengutronix.de>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Thanks,
Miquèl
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked
2018-09-13 5:58 [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked Masahiro Yamada
2018-09-14 14:29 ` Miquel Raynal
@ 2018-09-17 12:32 ` Boris Brezillon
1 sibling, 0 replies; 3+ messages in thread
From: Boris Brezillon @ 2018-09-17 12:32 UTC (permalink / raw)
To: Masahiro Yamada
Cc: linux-mtd, Miquel Raynal, Steffen Trumtrar, Marek Vasut,
Richard Weinberger, linux-kernel, Brian Norris, David Woodhouse
On Thu, 13 Sep 2018 14:58:49 +0900
Masahiro Yamada <yamada.masahiro@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.trumtrar@pengutronix.de>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@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);
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-09-17 12:32 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2018-09-13 5:58 [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked Masahiro Yamada
2018-09-14 14:29 ` Miquel Raynal
2018-09-17 12:32 ` Boris Brezillon
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