[PATCH v9 6/7] mfd: cros_ec: differentiate SCP from EC by feature bit.

[Pi-Hsun Shih]

System Companion Processor (SCP) is Cortex M4 co-processor on some
MediaTek platform that can run EC-style firmware. Since a SCP and EC
would both exist on a system, and use the cros_ec_dev driver, we need to
differentiate between them for the userspace, or they would both be
registered at /dev/cros_ec, causing a conflict.

Signed-off-by: Pi-Hsun Shih <pihsun@xxxxxxxxxxxx>

---
Changes from v8:
 - No change.

Changes from v7:
 - Address comments in v7.
 - Rebase the series onto https://lore.kernel.org/patchwork/patch/1059196/.

Changes from v6, v5, v4, v3, v2:
 - No change.

Changes from v1:
 - New patch extracted from Patch 5.
---
 drivers/mfd/cros_ec_dev.c            | 10 ++++++++++
 include/linux/mfd/cros_ec.h          |  1 +
 include/linux/mfd/cros_ec_commands.h |  2 +-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index a5391f96eafd..66107de3dbce 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -440,6 +440,16 @@ static int ec_device_probe(struct platform_device *pdev)
 		ec_platform->ec_name = CROS_EC_DEV_TP_NAME;
 	}
 
+	/* Check whether this is actually a SCP rather than an EC. */
+	if (cros_ec_check_features(ec, EC_FEATURE_SCP)) {
+		dev_info(dev, "CrOS SCP MCU detected.\n");
+		/*
+		 * Help userspace differentiating ECs from SCP,
+		 * regardless of the probing order.
+		 */
+		ec_platform->ec_name = CROS_EC_DEV_SCP_NAME;
+	}
+
 	/*
 	 * Add the class device
 	 * Link to the character device for creating the /dev entry
diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index cfa78bb4990f..751cb3756d49 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -27,6 +27,7 @@
 #define CROS_EC_DEV_PD_NAME "cros_pd"
 #define CROS_EC_DEV_TP_NAME "cros_tp"
 #define CROS_EC_DEV_ISH_NAME "cros_ish"
+#define CROS_EC_DEV_SCP_NAME "cros_scp"
 
 /*
  * The EC is unresponsive for a time after a reboot command.  Add a
diff --git a/include/linux/mfd/cros_ec_commands.h b/include/linux/mfd/cros_ec_commands.h
index dcec96f01879..8b578b4c1ec7 100644
--- a/include/linux/mfd/cros_ec_commands.h
+++ b/include/linux/mfd/cros_ec_commands.h
@@ -884,7 +884,7 @@ enum ec_feature_code {
 	EC_FEATURE_REFINED_TABLET_MODE_HYSTERESIS = 37,
 	/* EC supports audio codec. */
 	EC_FEATURE_AUDIO_CODEC = 38,
-	/* EC Supports SCP. */
+	/* The MCU is a System Companion Processor (SCP). */
 	EC_FEATURE_SCP = 39,
 	/* The MCU is an Integrated Sensor Hub */
 	EC_FEATURE_ISH = 40,
-- 
2.22.0.rc1.257.g3120a18244-goog