bus: mhi: host: Add sysfs entry to force device to enter EDL

Add sysfs entry to allow users of MHI bus to force device to enter EDL
(Emergency Download) mode to download the device firmware. Since there is
no guarantee that all the devices will support EDL mode, the sysfs entry
is kept as an optional one and will appear only for the supported devices.

Controllers supporting the EDL mode are expected to provide edl_trigger()
callback that puts the device into EDL mode.

Signed-off-by: Qiang Yu <quic_qianyu@quicinc.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1713928915-18229-2-git-send-email-quic_qianyu@quicinc.com
[mani: fixed the kernel version and reworded the commit message]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

3 files changed, 48 insertions, 0 deletions

diff --git a/Documentation/ABI/stable/sysfs-bus-mhi b/Documentation/ABI/stable/sysfs-bus-mhi
index 1a47f9e0cc845c..8b9698fa0bebf3 100644
--- a/Documentation/ABI/stable/sysfs-bus-mhi
+++ b/Documentation/ABI/stable/sysfs-bus-mhi
@@ -29,3 +29,16 @@ Description:	Initiates a SoC reset on the MHI controller.  A SoC reset is
                 This can be useful as a method of recovery if the device is
                 non-responsive, or as a means of loading new firmware as a
                 system administration task.
+
+What:           /sys/bus/mhi/devices/.../trigger_edl
+Date:           April 2024
+KernelVersion:  6.10
+Contact:        mhi@lists.linux.dev
+Description:    Writing a non-zero value to this file will force devices to
+                enter EDL (Emergency Download) mode. This entry only exists for
+                devices capable of entering the EDL mode using the standard EDL
+                triggering mechanism defined in the MHI spec v1.2. Once in EDL
+                mode, the flash programmer image can be downloaded to the
+                device to enter the flash programmer execution environment.
+                This can be useful if user wants to use QDL (Qualcomm Download,
+                which is used to download firmware over EDL) to update firmware.
diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
index 44f934981de82a..7104c185698762 100644
--- a/drivers/bus/mhi/host/init.c
+++ b/drivers/bus/mhi/host/init.c
@@ -127,6 +127,30 @@ static ssize_t soc_reset_store(struct device *dev,
 }
 static DEVICE_ATTR_WO(soc_reset);
 
+static ssize_t trigger_edl_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t count)
+{
+	struct mhi_device *mhi_dev = to_mhi_device(dev);
+	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret < 0)
+		return ret;
+
+	if (!val)
+		return -EINVAL;
+
+	ret = mhi_cntrl->edl_trigger(mhi_cntrl);
+	if (ret)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_WO(trigger_edl);
+
 static struct attribute *mhi_dev_attrs[] = {
 	&dev_attr_serial_number.attr,
 	&dev_attr_oem_pk_hash.attr,
@@ -1018,6 +1042,12 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
 	if (ret)
 		goto err_release_dev;
 
+	if (mhi_cntrl->edl_trigger) {
+		ret = sysfs_create_file(&mhi_dev->dev.kobj, &dev_attr_trigger_edl.attr);
+		if (ret)
+			goto err_release_dev;
+	}
+
 	mhi_cntrl->mhi_dev = mhi_dev;
 
 	mhi_create_debugfs(mhi_cntrl);
@@ -1051,6 +1081,9 @@ void mhi_unregister_controller(struct mhi_controller *mhi_cntrl)
 	mhi_deinit_free_irq(mhi_cntrl);
 	mhi_destroy_debugfs(mhi_cntrl);
 
+	if (mhi_cntrl->edl_trigger)
+		sysfs_remove_file(&mhi_dev->dev.kobj, &dev_attr_trigger_edl.attr);
+
 	destroy_workqueue(mhi_cntrl->hiprio_wq);
 	kfree(mhi_cntrl->mhi_cmd);
 	kfree(mhi_cntrl->mhi_event);
diff --git a/include/linux/mhi.h b/include/linux/mhi.h
index cde01e133a1b16..d968e1ab44dc50 100644
--- a/include/linux/mhi.h
+++ b/include/linux/mhi.h
@@ -353,6 +353,7 @@ struct mhi_controller_config {
  * @read_reg: Read a MHI register via the physical link (required)
  * @write_reg: Write a MHI register via the physical link (required)
  * @reset: Controller specific reset function (optional)
+ * @edl_trigger: CB function to trigger EDL mode (optional)
  * @buffer_len: Bounce buffer length
  * @index: Index of the MHI controller instance
  * @bounce_buf: Use of bounce buffer
@@ -435,6 +436,7 @@ struct mhi_controller {
 	void (*write_reg)(struct mhi_controller *mhi_cntrl, void __iomem *addr,
 			  u32 val);
 	void (*reset)(struct mhi_controller *mhi_cntrl);
+	int (*edl_trigger)(struct mhi_controller *mhi_cntrl);
 
 	size_t buffer_len;
 	int index;