mtd: bcm47xxsflash: use uncached MMIO access for BCM53573

BCM53573 is a new series of Broadcom's SoCs. It's based on ARM and uses
this old ChipCommon-based flash access. Early tests resulted in flash
corruptions that were tracked down to using cached MMIO for flash read
access. Switch to ioremap_nocache conditionally to support BCM53573 and
don't break performance on old MIPS devices.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/drivers/mtd/devices/bcm47xxsflash.c b/drivers/mtd/devices/bcm47xxsflash.c
index 1c65c15b31a1..514be04c0b6c 100644
--- a/drivers/mtd/devices/bcm47xxsflash.c
+++ b/drivers/mtd/devices/bcm47xxsflash.c
@@ -296,16 +296,30 @@ static int bcm47xxsflash_bcma_probe(struct platform_device *pdev)
                 dev_err(dev, "can't request region for resource %pR\n", res);
                 return -EBUSY;
         }
-        b47s->window = ioremap_cache(res->start, resource_size(res));
-        if (!b47s->window) {
-                dev_err(dev, "ioremap failed for resource %pR\n", res);
-                return -ENOMEM;
-        }
 
         b47s->bcma_cc = container_of(sflash, struct bcma_drv_cc, sflash);
         b47s->cc_read = bcm47xxsflash_bcma_cc_read;
         b47s->cc_write = bcm47xxsflash_bcma_cc_write;
 
+        /*
+         * On old MIPS devices cache was magically invalidated when needed,
+         * allowing us to use cached access and gain some performance. Trying
+         * the same on ARM based BCM53573 results in flash corruptions, we need
+         * to use uncached access for it.
+         *
+         * It may be arch specific, but right now there is only 1 ARM SoC using
+         * this driver, so let's follow Broadcom's reference code and check
+         * ChipCommon revision.
+         */
+        if (b47s->bcma_cc->core->id.rev == 54)
+                b47s->window = ioremap_nocache(res->start, resource_size(res));
+        else
+                b47s->window = ioremap_cache(res->start, resource_size(res));
+        if (!b47s->window) {
+                dev_err(dev, "ioremap failed for resource %pR\n", res);
+                return -ENOMEM;
+        }
+
         switch (b47s->bcma_cc->capabilities & BCMA_CC_CAP_FLASHT) {
         case BCMA_CC_FLASHT_STSER:
                 b47s->type = BCM47XXSFLASH_TYPE_ST;