target/linux/generic/patches-4.4/042-0003-mtd-bcm47xxsflash-use-uncached-MMIO-access-for-BCM53.patch

   1 From 64ad46379fcf14f437553f654d1adcd3d0e0d7f9 Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
   3 Date: Mon, 15 Aug 2016 14:21:28 +0200
   4 Subject: [PATCH] mtd: bcm47xxsflash: use uncached MMIO access for BCM53573
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 BCM53573 is a new series of Broadcom's SoCs. It's based on ARM and uses
  10 this old ChipCommon-based flash access. Early tests resulted in flash
  11 corruptions that were tracked down to using cached MMIO for flash read
  12 access. Switch to ioremap_nocache conditionally to support BCM53573 and
  13 don't break performance on old MIPS devices.
  14
  15 Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
  16 Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
  17 Signed-off-by: Brian Norris <computersforpeace@gmail.com>
  18 ---
  19  drivers/mtd/devices/bcm47xxsflash.c | 24 +++++++++++++++++++-----
  20  1 file changed, 19 insertions(+), 5 deletions(-)
  21
  22 --- a/drivers/mtd/devices/bcm47xxsflash.c
  23 +++ b/drivers/mtd/devices/bcm47xxsflash.c
  24 @@ -296,16 +296,30 @@ static int bcm47xxsflash_bcma_probe(stru
  25                 dev_err(dev, "can't request region for resource %pR\n", res);
  26                 return -EBUSY;
  27         }
  28 -       b47s->window = ioremap_cache(res->start, resource_size(res));
  29 -       if (!b47s->window) {
  30 -               dev_err(dev, "ioremap failed for resource %pR\n", res);
  31 -               return -ENOMEM;
  32 -       }
  33
  34         b47s->bcma_cc = container_of(sflash, struct bcma_drv_cc, sflash);
  35         b47s->cc_read = bcm47xxsflash_bcma_cc_read;
  36         b47s->cc_write = bcm47xxsflash_bcma_cc_write;
  37
  38 +       /*
  39 +        * On old MIPS devices cache was magically invalidated when needed,
  40 +        * allowing us to use cached access and gain some performance. Trying
  41 +        * the same on ARM based BCM53573 results in flash corruptions, we need
  42 +        * to use uncached access for it.
  43 +        *
  44 +        * It may be arch specific, but right now there is only 1 ARM SoC using
  45 +        * this driver, so let's follow Broadcom's reference code and check
  46 +        * ChipCommon revision.
  47 +        */
  48 +       if (b47s->bcma_cc->core->id.rev == 54)
  49 +               b47s->window = ioremap_nocache(res->start, resource_size(res));
  50 +       else
  51 +               b47s->window = ioremap_cache(res->start, resource_size(res));
  52 +       if (!b47s->window) {
  53 +               dev_err(dev, "ioremap failed for resource %pR\n", res);
  54 +               return -ENOMEM;
  55 +       }
  56 +
  57         switch (b47s->bcma_cc->capabilities & BCMA_CC_CAP_FLASHT) {
  58         case BCMA_CC_FLASHT_STSER:
  59                 b47s->type = BCM47XXSFLASH_TYPE_ST;