[PATCH RFC 1/2] scatterlist: add I/O variant of sg_pcopy & sg_copy

[Neil Armstrong <narmstrong@baylibre.com>]

When copying from/to an iomem mapped memory, the current sg_copy & sg_pcopy can't
be used and lead to local variants in drivers like in [1] & [2].

This introduces an I/O variant to be used instead of the local variants.

[1] mv_cesa_sg_copy in drivers/crypto/marvell/cesa/tdma.c
[2] meson_mmc_copy_buffer in drivers/mmc/host/meson-gx-mmc.c

Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 include/linux/scatterlist.h |  14 +++++
 lib/scatterlist.c           | 119 ++++++++++++++++++++++++++++++++++++
 2 files changed, 133 insertions(+)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 6f70572b2938..6ef339ba5290 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -308,15 +308,29 @@ void sgl_free(struct scatterlist *sgl);
 size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 		      size_t buflen, off_t skip, bool to_buffer);
 
+size_t sg_copy_io(struct scatterlist *sgl, unsigned int nents, void __iomem *buf,
+		  size_t buflen, off_t skip, bool to_buffer);
+
 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 			   const void *buf, size_t buflen);
 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 			 void *buf, size_t buflen);
 
+size_t sg_copy_from_io(struct scatterlist *sgl, unsigned int nents,
+		       const void __iomem *buf, size_t buflen);
+size_t sg_copy_to_io(struct scatterlist *sgl, unsigned int nents,
+		     void __iomem *buf, size_t buflen);
+
 size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 			    const void *buf, size_t buflen, off_t skip);
 size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 			  void *buf, size_t buflen, off_t skip);
+
+size_t sg_pcopy_from_io(struct scatterlist *sgl, unsigned int nents,
+			const void __iomem *buf, size_t buflen, off_t skip);
+size_t sg_pcopy_to_io(struct scatterlist *sgl, unsigned int nents,
+		      void __iomem *buf, size_t buflen, off_t skip);
+
 size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
 		       size_t buflen, off_t skip);
 
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index a59778946404..e52f37b181fa 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -954,6 +954,55 @@ size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
 }
 EXPORT_SYMBOL(sg_copy_buffer);
 
+/**
+ * sg_copy_io - Copy data between an I/O mapped buffer and an SG list
+ * @sgl:		 The SG list
+ * @nents:		 Number of SG entries
+ * @buf:		 Where to copy from
+ * @buflen:		 The number of bytes to copy
+ * @skip:		 Number of bytes to skip before copying
+ * @to_buffer:		 transfer direction (true == from an sg list to a
+ *			 buffer, false == from a buffer to an sg list)
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_copy_io(struct scatterlist *sgl, unsigned int nents, void __iomem *buf,
+		  size_t buflen, off_t skip, bool to_buffer)
+{
+	unsigned int offset = 0;
+	struct sg_mapping_iter miter;
+	unsigned int sg_flags = SG_MITER_ATOMIC;
+
+	if (to_buffer)
+		sg_flags |= SG_MITER_FROM_SG;
+	else
+		sg_flags |= SG_MITER_TO_SG;
+
+	sg_miter_start(&miter, sgl, nents, sg_flags);
+
+	if (!sg_miter_skip(&miter, skip))
+		return 0;
+
+	while ((offset < buflen) && sg_miter_next(&miter)) {
+		unsigned int len;
+
+		len = min(miter.length, buflen - offset);
+
+		if (to_buffer)
+			memcpy_toio(buf + offset, miter.addr, len);
+		else
+			memcpy_fromio(miter.addr, buf + offset, len);
+
+		offset += len;
+	}
+
+	sg_miter_stop(&miter);
+
+	return offset;
+}
+EXPORT_SYMBOL(sg_copy_io);
+
 /**
  * sg_copy_from_buffer - Copy from a linear buffer to an SG list
  * @sgl:		 The SG list
@@ -988,6 +1037,40 @@ size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 }
 EXPORT_SYMBOL(sg_copy_to_buffer);
 
+/**
+ * sg_copy_from_io - Copy from an I/O mapped buffer to an SG list
+ * @sgl:		 The SG list
+ * @nents:		 Number of SG entries
+ * @buf:		 Where to copy from
+ * @buflen:		 The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_copy_from_io(struct scatterlist *sgl, unsigned int nents,
+		       const void *buf, size_t buflen)
+{
+	return sg_copy_io(sgl, nents, (void __iomem *)buf, buflen, 0, false);
+}
+EXPORT_SYMBOL(sg_copy_from_io);
+
+/**
+ * sg_copy_to_io - Copy from an SG list to an I/O mapped buffer
+ * @sgl:		 The SG list
+ * @nents:		 Number of SG entries
+ * @buf:		 Where to copy to
+ * @buflen:		 The number of bytes to copy
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_copy_to_io(struct scatterlist *sgl, unsigned int nents,
+		     void __iomem *buf, size_t buflen)
+{
+	return sg_copy_io(sgl, nents, buf, buflen, 0, true);
+}
+EXPORT_SYMBOL(sg_copy_to_io);
+
 /**
  * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
  * @sgl:		 The SG list
@@ -1024,6 +1107,42 @@ size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 }
 EXPORT_SYMBOL(sg_pcopy_to_buffer);
 
+/**
+ * sg_pcopy_from_io - Copy from an I/O mapped buffer to an SG list
+ * @sgl:		 The SG list
+ * @nents:		 Number of SG entries
+ * @buf:		 Where to copy from
+ * @buflen:		 The number of bytes to copy
+ * @skip:		 Number of bytes to skip before copying
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_from_io(struct scatterlist *sgl, unsigned int nents,
+			const void __iomem *buf, size_t buflen, off_t skip)
+{
+	return sg_copy_io(sgl, nents, (void __iomem *)buf, buflen, skip, false);
+}
+EXPORT_SYMBOL(sg_pcopy_from_io);
+
+/**
+ * sg_pcopy_to_io - Copy from an SG list to an I/O mapped buffer
+ * @sgl:		 The SG list
+ * @nents:		 Number of SG entries
+ * @buf:		 Where to copy to
+ * @buflen:		 The number of bytes to copy
+ * @skip:		 Number of bytes to skip before copying
+ *
+ * Returns the number of copied bytes.
+ *
+ **/
+size_t sg_pcopy_to_io(struct scatterlist *sgl, unsigned int nents,
+		      void __iomem *buf, size_t buflen, off_t skip)
+{
+	return sg_copy_io(sgl, nents, buf, buflen, skip, true);
+}
+EXPORT_SYMBOL(sg_pcopy_to_io);
+
 /**
  * sg_zero_buffer - Zero-out a part of a SG list
  * @sgl:		 The SG list
-- 
2.25.1