From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: linux-mtd@lists.infradead.org,
Boris Brezillon <boris.brezillon@bootlin.com>,
Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
linux-kernel@vger.kernel.org, Marek Vasut <marek.vasut@gmail.com>,
Brian Norris <computersforpeace@gmail.com>,
Richard Weinberger <richard@nod.at>,
David Woodhouse <dwmw2@infradead.org>
Subject: [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked
Date: Thu, 13 Sep 2018 14:58:49 +0900 [thread overview]
Message-ID: <1536818329-11068-1-git-send-email-yamada.masahiro@socionext.com> (raw)
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
next reply other threads:[~2018-09-13 6:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-13 5:58 Masahiro Yamada [this message]
2018-09-14 14:29 ` [PATCH] mtd: rawnand: denali: fix a race condition when DMA is kicked Miquel Raynal
2018-09-17 12:32 ` Boris Brezillon
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