lib/iomap_copy.c: add __ioread32_copy()

Some drivers need to read data out of iomem areas 32-bits at a time.
Add an API to do this.
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Cc: <zajec5@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/io.h

@@ -29,6 +29,7 @@ struct device;
 struct resource;
 
 __visible void __iowrite32_copy(void __iomem *to, const void *from, size_t count);
+void __ioread32_copy(void *to, const void __iomem *from, size_t count);
 void __iowrite64_copy(void __iomem *to, const void *from, size_t count);
 
 #ifdef CONFIG_MMU

lib/iomap_copy.c

@@ -41,6 +41,27 @@ void __attribute__((weak)) __iowrite32_copy(void __iomem *to,
 }
 EXPORT_SYMBOL_GPL(__iowrite32_copy);
 
+/**
+ * __ioread32_copy - copy data from MMIO space, in 32-bit units
+ * @to: destination (must be 32-bit aligned)
+ * @from: source, in MMIO space (must be 32-bit aligned)
+ * @count: number of 32-bit quantities to copy
+ *
+ * Copy data from MMIO space to kernel space, in units of 32 bits at a
+ * time.  Order of access is not guaranteed, nor is a memory barrier
+ * performed afterwards.
+ */
+void __ioread32_copy(void *to, const void __iomem *from, size_t count)
+{
+	u32 *dst = to;
+	const u32 __iomem *src = from;
+	const u32 __iomem *end = src + count;
+
+	while (src < end)
+		*dst++ = __raw_readl(src++);
+}
+EXPORT_SYMBOL_GPL(__ioread32_copy);
+
 /**
  * __iowrite64_copy - copy data to MMIO space, in 64-bit or 32-bit units
  * @to: destination, in MMIO space (must be 64-bit aligned)