soc: qcom: aoss: Move length requirements from caller

The existing implementation of qmp_send() requires the caller to provide
a buffer which is of word-aligned. The underlying reason for this is
that message ram only supports word accesses, but pushing this
requirement onto the clients results in the same boiler plate code
sprinkled in every call site.

By using a temporary buffer in qmp_send() we can hide the underlying
hardware limitations from the clients and allow them to pass their
NUL-terminates C string directly.

Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230811205839.727373-2-quic_bjorande@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: quic-bjorande

drivers/net/ipa/ipa_power.c

@@ -332,7 +332,7 @@ void ipa_power_retention(struct ipa *ipa, bool enable)
 
 	(void)snprintf(buf, sizeof(buf), fmt, enable ? '1' : '0');
 
-	ret = qmp_send(power->qmp, buf, sizeof(buf));
+	ret = qmp_send(power->qmp, buf);
 	if (ret)
 		dev_err(power->dev, "error %d sending QMP %sable request\n",
 			ret, enable ? "en" : "dis");

drivers/remoteproc/qcom_q6v5.c

@@ -35,7 +35,7 @@ static int q6v5_load_state_toggle(struct qcom_q6v5 *q6v5, bool enable)
 
 	WARN_ON(ret >= Q6V5_LOAD_STATE_MSG_LEN);
 
-	ret = qmp_send(q6v5->qmp, buf, sizeof(buf));
+	ret = qmp_send(q6v5->qmp, buf);
 	if (ret)
 		dev_err(q6v5->dev, "failed to toggle load state\n");
 

drivers/soc/qcom/qcom_aoss.c

@@ -206,36 +206,35 @@ static bool qmp_message_empty(struct qmp *qmp)
  * qmp_send() - send a message to the AOSS
  * @qmp: qmp context
  * @data: message to be sent
- * @len: length of the message
  *
  * Transmit @data to AOSS and wait for the AOSS to acknowledge the message.
- * @len must be a multiple of 4 and not longer than the mailbox size. Access is
- * synchronized by this implementation.
+ * data must not be longer than the mailbox size. Access is synchronized by
+ * this implementation.
  *
  * Return: 0 on success, negative errno on failure
  */
-int qmp_send(struct qmp *qmp, const void *data, size_t len)
+int qmp_send(struct qmp *qmp, const void *data)
 {
+	char buf[QMP_MSG_LEN];
 	long time_left;
 	int ret;
 
 	if (WARN_ON(IS_ERR_OR_NULL(qmp) || !data))
 		return -EINVAL;
 
-	if (WARN_ON(len + sizeof(u32) > qmp->size))
+	if (WARN_ON(strlen(data) >= sizeof(buf)))
 		return -EINVAL;
 
-	if (WARN_ON(len % sizeof(u32)))
-		return -EINVAL;
+	strscpy_pad(buf, data, sizeof(buf));
 
 	mutex_lock(&qmp->tx_lock);
 
 	/* The message RAM only implements 32-bit accesses */
 	__iowrite32_copy(qmp->msgram + qmp->offset + sizeof(u32),
-			 data, len / sizeof(u32));
-	writel(len, qmp->msgram + qmp->offset);
+			 buf, sizeof(buf) / sizeof(u32));
+	writel(sizeof(buf), qmp->msgram + qmp->offset);
 
-	/* Read back len to confirm data written in message RAM */
+	/* Read back length to confirm data written in message RAM */
 	readl(qmp->msgram + qmp->offset);
 	qmp_kick(qmp);
 
@@ -262,15 +261,15 @@ static int qmp_qdss_clk_prepare(struct clk_hw *hw)
 	static const char buf[QMP_MSG_LEN] = "{class: clock, res: qdss, val: 1}";
 	struct qmp *qmp = container_of(hw, struct qmp, qdss_clk);
 
-	return qmp_send(qmp, buf, sizeof(buf));
+	return qmp_send(qmp, buf);
 }
 
 static void qmp_qdss_clk_unprepare(struct clk_hw *hw)
 {
 	static const char buf[QMP_MSG_LEN] = "{class: clock, res: qdss, val: 0}";
 	struct qmp *qmp = container_of(hw, struct qmp, qdss_clk);
 
-	qmp_send(qmp, buf, sizeof(buf));
+	qmp_send(qmp, buf);
 }
 
 static const struct clk_ops qmp_qdss_clk_ops = {
@@ -344,7 +343,7 @@ static int qmp_cdev_set_cur_state(struct thermal_cooling_device *cdev,
 			qmp_cdev->name,
 			cdev_state ? "on" : "off");
 
-	ret = qmp_send(qmp_cdev->qmp, buf, sizeof(buf));
+	ret = qmp_send(qmp_cdev->qmp, buf);
 
 	if (!ret)
 		qmp_cdev->state = cdev_state;

include/linux/soc/qcom/qcom_aoss.h

@@ -13,13 +13,13 @@ struct qmp;
 
 #if IS_ENABLED(CONFIG_QCOM_AOSS_QMP)
 
-int qmp_send(struct qmp *qmp, const void *data, size_t len);
+int qmp_send(struct qmp *qmp, const void *data);
 struct qmp *qmp_get(struct device *dev);
 void qmp_put(struct qmp *qmp);
 
 #else
 
-static inline int qmp_send(struct qmp *qmp, const void *data, size_t len)
+static inline int qmp_send(struct qmp *qmp, const void *data)
 {
 	return -ENODEV;
 }