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.

Acked-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.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);
 }