Re: [PATCH v17 1/8] drm: bridge: Cadence: Create mhdp helper driver

MHDP8546 mailbox access functions will be share to other mhdp driver
and Cadence HDP-TX HDMI/DP PHY drivers.
Create a new mhdp helper driver and move all those functions into.

cdns_mhdp_reg_write() is renamed to cdns_mhdp_dp_reg_write(),
because it use the DPTX command ID DPTX_WRITE_REGISTER.

New cdns_mhdp_reg_write() is created with the general command ID
GENERAL_REGISTER_WRITE.

Rewrite cdns_mhdp_set_firmware_active() in mhdp8546 core driver,
use cdns_mhdp_mailbox_send() to replace cdns_mhdp_mailbox_write()
same as the other mailbox access functions.

Replaces the local mutex mbox_mutex with a global mutex mhdp_mailbox_mutex
to prevent race conditions in mailbox access by multi drivers.

Signed-off-by: Sandor Yu <redacted>
---
v16->v17:
- Replaces the local mutex mbox_mutex with a global mutex mhdp_mailbox_mutex

v12->v16:
 *No change.

V11->v12:
- Move status initialize out of mbox_mutex.
- Reorder API functions in alphabetical.
- Add notes for malibox access functions.
- Add year 2024 to copyright.

 drivers/gpu/drm/bridge/cadence/Kconfig        |   4 +
 drivers/gpu/drm/bridge/cadence/Makefile       |   1 +
 .../gpu/drm/bridge/cadence/cdns-mhdp-helper.c | 307 +++++++++++++
 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 425 ++++--------------
 .../drm/bridge/cadence/cdns-mhdp8546-core.h   |  47 +-
 .../drm/bridge/cadence/cdns-mhdp8546-hdcp.c   |  36 +-
 include/drm/bridge/cdns-mhdp-helper.h         |  94 ++++
 7 files changed, 507 insertions(+), 407 deletions(-)
 create mode 100644 drivers/gpu/drm/bridge/cadence/cdns-mhdp-helper.c
 create mode 100644 include/drm/bridge/cdns-mhdp-helper.h

diff --git a/drivers/gpu/drm/bridge/cadence/Kconfig b/drivers/gpu/drm/bridge/cadence/Kconfig
index cced81633ddcd..e0973339e9e33 100644
--- a/drivers/gpu/drm/bridge/cadence/Kconfig
+++ b/drivers/gpu/drm/bridge/cadence/Kconfig

@@ -21,6 +21,9 @@ config DRM_CDNS_DSI_J721E
 	  the routing of the DSS DPI signal to the Cadence DSI.
 endif
 
+config CDNS_MHDP_HELPER
+	tristate
+
 config DRM_CDNS_MHDP8546
 	tristate "Cadence DPI/DP bridge"
 	select DRM_DISPLAY_DP_HELPER

@@ -28,6 +31,7 @@ config DRM_CDNS_MHDP8546
 	select DRM_DISPLAY_HELPER
 	select DRM_KMS_HELPER
 	select DRM_PANEL_BRIDGE
+	select CDNS_MHDP_HELPER
 	depends on OF
 	help
 	  Support Cadence DPI to DP bridge. This is an internal

diff --git a/drivers/gpu/drm/bridge/cadence/Makefile b/drivers/gpu/drm/bridge/cadence/Makefile
index c95fd5b81d137..087dc074820d7 100644
--- a/drivers/gpu/drm/bridge/cadence/Makefile
+++ b/drivers/gpu/drm/bridge/cadence/Makefile

@@ -2,6 +2,7 @@
 obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
 cdns-dsi-y := cdns-dsi-core.o
 cdns-dsi-$(CONFIG_DRM_CDNS_DSI_J721E) += cdns-dsi-j721e.o
+obj-$(CONFIG_CDNS_MHDP_HELPER) += cdns-mhdp-helper.o
 obj-$(CONFIG_DRM_CDNS_MHDP8546) += cdns-mhdp8546.o
 cdns-mhdp8546-y := cdns-mhdp8546-core.o cdns-mhdp8546-hdcp.o
 cdns-mhdp8546-$(CONFIG_DRM_CDNS_MHDP8546_J721E) += cdns-mhdp8546-j721e.o

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp-helper.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp-helper.c
new file mode 100644
index 0000000000000..c60a6b69a5343
--- /dev/null
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp-helper.c

@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023, 2024 NXP Semiconductor, Inc.
+ *
+ */
+#include <drm/bridge/cdns-mhdp-helper.h>
+#include <linux/dev_printk.h>
+#include <linux/module.h>
+
+/* Protects mailbox communications with the firmware */
+DEFINE_MUTEX(mhdp_mailbox_mutex);