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>

diff --git a/drivers/mtd/devices/bcm47xxsflash.c b/drivers/mtd/devices/bcm47xxsflash.c
index 1c65c15b31a1aaed713363d5430c917754b13f13..514be04c0b6cc64962c1c4a4b2947346c5fa05dd 100644 (file)
--- 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;