rpmsg: glink: Allow unaligned data access

Glink protocol requires that each message is aligned
on a 8 byte offset. This is purely a restriction
from glink, so in order to support clients which
do not adher to this, allow data packets of any size,
but align the head index accordingly, effectively
removing the alignment restriction.

Change-Id: I41a319d2822277c10eef54444aa003ff191b1a95
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>

drivers/rpmsg/qcom_glink_native.c

@@ -227,9 +227,6 @@ static int qcom_glink_tx(struct qcom_glink *glink,
 	if (tlen >= glink->tx_pipe->length)
 		return -EINVAL;
 
-	if (WARN(tlen % 8, "Unaligned TX request"))
-		return -EINVAL;
-
 	ret = mutex_lock_interruptible(&glink->tx_lock);
 	if (ret)
 		return ret;
@@ -695,9 +692,6 @@ static int __qcom_glink_send(struct glink_channel *channel,
 		__le32 left_size;
 	} __packed req;
 
-	if (WARN(len % 8, "RPM GLINK expects 8 byte aligned messages\n"))
-		return -EINVAL;
-
 	req.msg.cmd = cpu_to_le16(RPM_CMD_TX_DATA);
 	req.msg.param1 = cpu_to_le16(channel->lcid);
 	req.msg.param2 = cpu_to_le32(channel->rcid);

drivers/rpmsg/qcom_glink_rpm.c

@@ -156,11 +156,31 @@ static void glink_rpm_tx_write(struct qcom_glink_pipe *glink_pipe,
 			       const void *data, size_t dlen)
 {
 	struct glink_rpm_pipe *pipe = to_rpm_pipe(glink_pipe);
+	size_t tlen = hlen + dlen;
+	size_t aligned_dlen;
 	unsigned int head;
+	char padding[8] = {0};
+	size_t pad;
+
+	/* Header length comes from glink native and is always 4 byte aligned */
+	if (WARN(hlen % 4, "Glink Header length must be 4 bytes aligned\n"))
+		return;
+
+	/*
+	 * Move the unaligned tail of the message to the padding chunk, to
+	 * ensure word aligned accesses
+	 */
+	aligned_dlen = ALIGN_DOWN(dlen, 4);
+	if (aligned_dlen != dlen)
+		memcpy(padding, data + aligned_dlen, dlen - aligned_dlen);
 
 	head = readl(pipe->head);
 	head = glink_rpm_tx_write_one(pipe, head, hdr, hlen);
-	head = glink_rpm_tx_write_one(pipe, head, data, dlen);
+	head = glink_rpm_tx_write_one(pipe, head, data, aligned_dlen);
+
+	pad = ALIGN(tlen, 8) - ALIGN_DOWN(tlen, 4);
+	if (pad)
+		head = glink_rpm_tx_write_one(pipe, head, padding, pad);
 	writel(head, pipe->head);
 }