remoteproc: Add a rproc_set_firmware() API

A new API, rproc_set_firmware() is added to allow the remoteproc platform
drivers and remoteproc client drivers to be able to configure a custom
firmware name that is different from the default name used during
remoteproc registration. This function is being introduced to provide
a kernel-level equivalent of the current sysfs interface to remoteproc
client drivers, and can only change firmwares when the remoteproc is
offline. This allows some remoteproc drivers to choose different firmwares
at runtime based on the functionality the remote processor is providing.
The TI PRU Ethernet driver will be an example of such usage as it
requires to use different firmwares for different supported protocols.

Also, update the firmware_store() function used by the sysfs interface
to reuse this function to avoid code duplication.

Reviewed-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20201121032042.6195-1-s-anna@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1934,6 +1934,69 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
 #endif
 EXPORT_SYMBOL(rproc_get_by_phandle);
 
+/**
+ * rproc_set_firmware() - assign a new firmware
+ * @rproc: rproc handle to which the new firmware is being assigned
+ * @fw_name: new firmware name to be assigned
+ *
+ * This function allows remoteproc drivers or clients to configure a custom
+ * firmware name that is different from the default name used during remoteproc
+ * registration. The function does not trigger a remote processor boot,
+ * only sets the firmware name used for a subsequent boot. This function
+ * should also be called only when the remote processor is offline.
+ *
+ * This allows either the userspace to configure a different name through
+ * sysfs or a kernel-level remoteproc or a remoteproc client driver to set
+ * a specific firmware when it is controlling the boot and shutdown of the
+ * remote processor.
+ *
+ * Return: 0 on success or a negative value upon failure
+ */
+int rproc_set_firmware(struct rproc *rproc, const char *fw_name)
+{
+	struct device *dev;
+	int ret, len;
+	char *p;
+
+	if (!rproc || !fw_name)
+		return -EINVAL;
+
+	dev = rproc->dev.parent;
+
+	ret = mutex_lock_interruptible(&rproc->lock);
+	if (ret) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
+		return -EINVAL;
+	}
+
+	if (rproc->state != RPROC_OFFLINE) {
+		dev_err(dev, "can't change firmware while running\n");
+		ret = -EBUSY;
+		goto out;
+	}
+
+	len = strcspn(fw_name, "\n");
+	if (!len) {
+		dev_err(dev, "can't provide empty string for firmware name\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	p = kstrndup(fw_name, len, GFP_KERNEL);
+	if (!p) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	kfree(rproc->firmware);
+	rproc->firmware = p;
+
+out:
+	mutex_unlock(&rproc->lock);
+	return ret;
+}
+EXPORT_SYMBOL(rproc_set_firmware);
+
 static int rproc_validate(struct rproc *rproc)
 {
 	switch (rproc->state) {

drivers/remoteproc/remoteproc_sysfs.c

@@ -154,38 +154,9 @@ static ssize_t firmware_store(struct device *dev,
 			      const char *buf, size_t count)
 {
 	struct rproc *rproc = to_rproc(dev);
-	char *p;
-	int err, len = count;
+	int err;
 
-	err = mutex_lock_interruptible(&rproc->lock);
-	if (err) {
-		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, err);
-		return -EINVAL;
-	}
-
-	if (rproc->state != RPROC_OFFLINE) {
-		dev_err(dev, "can't change firmware while running\n");
-		err = -EBUSY;
-		goto out;
-	}
-
-	len = strcspn(buf, "\n");
-	if (!len) {
-		dev_err(dev, "can't provide a NULL firmware\n");
-		err = -EINVAL;
-		goto out;
-	}
-
-	p = kstrndup(buf, len, GFP_KERNEL);
-	if (!p) {
-		err = -ENOMEM;
-		goto out;
-	}
-
-	kfree(rproc->firmware);
-	rproc->firmware = p;
-out:
-	mutex_unlock(&rproc->lock);
+	err = rproc_set_firmware(rproc, buf);
 
 	return err ? err : count;
 }

include/linux/remoteproc.h

@@ -653,6 +653,7 @@ rproc_of_resm_mem_entry_init(struct device *dev, u32 of_resm_idx, size_t len,
 
 int rproc_boot(struct rproc *rproc);
 void rproc_shutdown(struct rproc *rproc);
+int rproc_set_firmware(struct rproc *rproc, const char *fw_name);
 void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type);
 int rproc_coredump_add_segment(struct rproc *rproc, dma_addr_t da, size_t size);
 int rproc_coredump_add_custom_segment(struct rproc *rproc,