kernel: add BCM53573 flash fix sent upstream

This fixes flash corruptions. It touches bcm47xxsflash driver shared
between brcm47xx and bcm53xx so put it in generic.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/generic/patches-4.4/143-mtd-bcm47xxsflash-use-uncached-MMIO-access-for-BCM53.patch

@@ -0,0 +1,57 @@
+From 77fab8f7dc756ba65f37145c493cc04f17e36bea Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Mon, 15 Aug 2016 14:13:09 +0200
+Subject: [PATCH] mtd: bcm47xxsflash: use uncached MMIO access for BCM53573
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+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>
+---
+ drivers/mtd/devices/bcm47xxsflash.c | 24 +++++++++++++++++++-----
+ 1 file changed, 19 insertions(+), 5 deletions(-)
+
+--- a/drivers/mtd/devices/bcm47xxsflash.c
++++ b/drivers/mtd/devices/bcm47xxsflash.c
+@@ -296,16 +296,30 @@ static int bcm47xxsflash_bcma_probe(stru
+ 		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;