releases/4.18.11/mtd-rawnand-denali-fix-a-race-condition-when-dma-is-kicked.patch

   1 From cf51e4b9c34407bf0c3d9b582b7837e047e1df47 Mon Sep 17 00:00:00 2001
   2 From: Masahiro Yamada <yamada.masahiro@socionext.com>
   3 Date: Thu, 13 Sep 2018 14:58:49 +0900
   4 Subject: mtd: rawnand: denali: fix a race condition when DMA is kicked
   5
   6 From: Masahiro Yamada <yamada.masahiro@socionext.com>
   7
   8 commit cf51e4b9c34407bf0c3d9b582b7837e047e1df47 upstream.
   9
  10 I thought the read-back of the DMA_ENABLE register was unnecessary
  11 (at least it is working on my boards), then deleted it in commit
  12 586a2c52909d ("mtd: nand: denali: squash denali_enable_dma() helper
  13 into caller").  Sorry, I was wrong - it caused a timing issue on
  14 Cyclone5 SoCFPGAs.
  15
  16 Revive the register read-back, commenting why this is necessary.
  17
  18 Fixes: 586a2c52909d ("mtd: nand: denali: squash denali_enable_dma() helper into caller")
  19 Cc: <stable@vger.kernel.org>
  20 Reported-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
  21 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
  22 Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
  23 Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
  24 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  25
  26 ---
  27  drivers/mtd/nand/raw/denali.c |    6 ++++++
  28  1 file changed, 6 insertions(+)
  29
  30 --- a/drivers/mtd/nand/raw/denali.c
  31 +++ b/drivers/mtd/nand/raw/denali.c
  32 @@ -604,6 +604,12 @@ static int denali_dma_xfer(struct denali
  33         }
  34
  35         iowrite32(DMA_ENABLE__FLAG, denali->reg + DMA_ENABLE);
  36 +       /*
  37 +        * The ->setup_dma() hook kicks DMA by using the data/command
  38 +        * interface, which belongs to a different AXI port from the
  39 +        * register interface.  Read back the register to avoid a race.
  40 +        */
  41 +       ioread32(denali->reg + DMA_ENABLE);
  42
  43         denali_reset_irq(denali);
  44         denali->setup_dma(denali, dma_addr, page, write);