[PATCH 2/2] soundwire: bus: Update sdw_nread/nwrite_no_pm to handle page boundaries

[Charles Keepax <ckeepax@opensource.cirrus.com>]

Currently issuing a sdw_nread/nwrite_no_pm across a page boundary
will silently fail to write correctly as nothing updates the page
registers, meaning the same page of the chip will get rewritten
with each successive page of data.

As the sdw_msg structure contains page information it seems
reasonable that a single sdw_msg should always be within one
page. It is also mostly simpler to handle the paging at the
bus level rather than each master having to handle it in their
xfer_msg callback.

As such add handling to the bus code to split up a transfer into
multiple sdw_msg's when they go across page boundaries.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
---
 drivers/soundwire/bus.c | 47 +++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 3c67266f94834..bdd251e871694 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -386,37 +386,42 @@ int sdw_fill_msg(struct sdw_msg *msg, struct sdw_slave *slave,
  * Read/Write IO functions.
  */
 
-int sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+static int sdw_ntransfer_no_pm(struct sdw_slave *slave, u32 addr, u8 flags,
+			       size_t count, u8 *val)
 {
 	struct sdw_msg msg;
+	size_t size;
 	int ret;
 
-	ret = sdw_fill_msg(&msg, slave, addr, count,
-			   slave->dev_num, SDW_MSG_FLAG_READ, val);
-	if (ret < 0)
-		return ret;
+	while (count) {
+		// Only handle bytes up to next page boundary
+		size = min(count, (SDW_REGADDR + 1) - (addr & SDW_REGADDR));
 
-	ret = sdw_transfer(slave->bus, &msg);
-	if (slave->is_mockup_device)
-		ret = 0;
-	return ret;
+		ret = sdw_fill_msg(&msg, slave, addr, size, slave->dev_num, flags, val);
+		if (ret < 0)
+			return ret;
+
+		ret = sdw_transfer(slave->bus, &msg);
+		if (ret < 0 && !slave->is_mockup_device)
+			return ret;
+
+		addr += size;
+		val += size;
+		count -= size;
+	}
+
+	return 0;
+}
+
+int sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+{
+	return sdw_ntransfer_no_pm(slave, addr, SDW_MSG_FLAG_READ, count, val);
 }
 EXPORT_SYMBOL(sdw_nread_no_pm);
 
 int sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
 {
-	struct sdw_msg msg;
-	int ret;
-
-	ret = sdw_fill_msg(&msg, slave, addr, count,
-			   slave->dev_num, SDW_MSG_FLAG_WRITE, (u8 *)val);
-	if (ret < 0)
-		return ret;
-
-	ret = sdw_transfer(slave->bus, &msg);
-	if (slave->is_mockup_device)
-		ret = 0;
-	return ret;
+	return sdw_ntransfer_no_pm(slave, addr, SDW_MSG_FLAG_WRITE, count, (u8 *)val);
 }
 EXPORT_SYMBOL(sdw_nwrite_no_pm);
 
-- 
2.30.2