[PATCH v5 0/3] Add Amlogic secure monitor driver

[PATCH v5 0/3] Add Amlogic secure monitor driver

[Carlo Caione]

From: Carlo Caione <carlo@endlessm.com>

In the Amlogic SoCs the secure monitor calls are used for a lot of reasons:
interact with the NVMEM (efuses), check the reboot reason, set USB boot, ...

This driver defines a generic interface towards the secure monitor that can be
used by more specialized drivers to interact with the secure monitor itself
without worrying about bounce buffers managing.

Changelog:

v5:
  * Moved IDs from DT to header file
  * Made read/write bounce buffers not mandatory
  * Introduced helper meson_sm_map_shmem()

v4:
  * Changed patches order
  * Removed now useless PATCH 2/4
  * Changed compatible to be SoC-specific
  * In the DT now we use SoC-agnostic IDs for the SMC functions. These IDs are
    traslated into SoC specific function IDs inside the driver
  * Added error checking on meson_sm_call() to retrieve the base address
  * Improved printing on errors

v3:
  * Moved driver to drivers/firmware
  * Added EXPORT_SYMBOL macros
  * Changed '_' in '-'
  * Introduced 'struct meson_sm_firmware' and 'meson_sm_get_fw()' to be used by
    drivers using the secure-monitor to enforce probe ordering

v2:
  * All the SMC function identifiers are now in a SoC-specific header file to
    be included by the DTS files so the SMC commands are now defined in the DT
    instead to be hardcoded into the driver
  * Patchset is no longer an RFC
  * Better error management and boundary checking
  * s/unsigned int/u32/
  * SMC call not only on CPU 0
  * Fix memory leaking
  * s/amlogic/meson/ in the directory names


Carlo Caione (3):
  firmware: Amlogic: Add secure monitor driver
  documentation: Add secure monitor binding documentation
  ARM64: dts: amlogic: gxbb: Enable secure monitor

 .../bindings/firmware/meson/meson_sm.txt           |  33 +++
 arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi        |   8 +
 drivers/firmware/Kconfig                           |   1 +
 drivers/firmware/Makefile                          |   1 +
 drivers/firmware/meson/Kconfig                     |   8 +
 drivers/firmware/meson/Makefile                    |   1 +
 drivers/firmware/meson/meson_sm.c                  | 223 +++++++++++++++++++++
 include/linux/firmware/meson/meson_sm.h            |  32 +++
 8 files changed, 307 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
 create mode 100644 drivers/firmware/meson/Kconfig
 create mode 100644 drivers/firmware/meson/Makefile
 create mode 100644 drivers/firmware/meson/meson_sm.c
 create mode 100644 include/linux/firmware/meson/meson_sm.h

-- 
2.7.4

[PATCH v5 1/3] firmware: Amlogic: Add secure monitor driver

[Carlo Caione]

From: Carlo Caione <carlo@endlessm.com>

Introduce a driver to provide calls into secure monitor mode.

In the Amlogic SoCs these calls are used for multiple reasons: access to
NVMEM, set USB boot, enable JTAG, etc...

Signed-off-by: Carlo Caione <carlo@endlessm.com>
---
 drivers/firmware/Kconfig                |   1 +
 drivers/firmware/Makefile               |   1 +
 drivers/firmware/meson/Kconfig          |   8 ++
 drivers/firmware/meson/Makefile         |   1 +
 drivers/firmware/meson/meson_sm.c       | 223 ++++++++++++++++++++++++++++++++
 include/linux/firmware/meson/meson_sm.h |  32 +++++
 6 files changed, 266 insertions(+)
 create mode 100644 drivers/firmware/meson/Kconfig
 create mode 100644 drivers/firmware/meson/Makefile
 create mode 100644 drivers/firmware/meson/meson_sm.c
 create mode 100644 include/linux/firmware/meson/meson_sm.h

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 6664f11..686e395 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -199,5 +199,6 @@ config HAVE_ARM_SMCCC
 source "drivers/firmware/broadcom/Kconfig"
 source "drivers/firmware/google/Kconfig"
 source "drivers/firmware/efi/Kconfig"
+source "drivers/firmware/meson/Kconfig"
 
 endmenu
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 474bada..fc4bb09 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_QCOM_SCM_32)	+= qcom_scm-32.o
 CFLAGS_qcom_scm-32.o :=$(call as-instr,.arch armv7-a\n.arch_extension sec,-DREQUIRES_SEC=1) -march=armv7-a
 
 obj-y				+= broadcom/
+obj-y				+= meson/
 obj-$(CONFIG_GOOGLE_FIRMWARE)	+= google/
 obj-$(CONFIG_EFI)		+= efi/
 obj-$(CONFIG_UEFI_CPER)		+= efi/
diff --git a/drivers/firmware/meson/Kconfig b/drivers/firmware/meson/Kconfig
new file mode 100644
index 0000000..fff11a3
--- /dev/null
+++ b/drivers/firmware/meson/Kconfig
@@ -0,0 +1,8 @@
+#
+# Amlogic Secure Monitor driver
+#
+config MESON_SM
+	bool
+	default ARCH_MESON
+	help
+	  Say y here to enable the Amlogic secure monitor driver
diff --git a/drivers/firmware/meson/Makefile b/drivers/firmware/meson/Makefile
new file mode 100644
index 0000000..9ab3884
--- /dev/null
+++ b/drivers/firmware/meson/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_MESON_SM) +=	meson_sm.o
diff --git a/drivers/firmware/meson/meson_sm.c b/drivers/firmware/meson/meson_sm.c
new file mode 100644
index 0000000..e1ce487
--- /dev/null
+++ b/drivers/firmware/meson/meson_sm.c
@@ -0,0 +1,223 @@
+/*
+ * Amlogic Secure Monitor driver
+ *
+ * Copyright (C) 2016 Endless Mobile, Inc.
+ * Author: Carlo Caione <carlo@endlessm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdarg.h>
+#include <asm/cacheflush.h>
+#include <asm/compiler.h>
+#include <linux/arm-smccc.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/smp.h>
+#include <linux/firmware/meson/meson_sm.h>
+
+struct meson_sm_cmd {
+	unsigned int index;
+	u32 smc_id;
+};
+#define CMD(d, s) { .index = (d), .smc_id = (s), }
+
+struct meson_sm_chip {
+	unsigned int shmem_size;
+	u32 cmd_shmem_in_base;
+	u32 cmd_shmem_out_base;
+	struct meson_sm_cmd cmd[];
+};
+
+struct meson_sm_firmware {
+	struct device *dev;
+	const struct meson_sm_chip *chip;
+	void __iomem *sm_shmem_in_base;
+	void __iomem *sm_shmem_out_base;
+};
+
+struct meson_sm_chip gxbb_chip = {
+	.shmem_size		= 0x1000,
+	.cmd_shmem_in_base	= 0x82000020,
+	.cmd_shmem_out_base	= 0x82000021,
+	.cmd = {
+		CMD(SM_EFUSE_READ,	0x82000030),
+		CMD(SM_EFUSE_WRITE,	0x82000031),
+		CMD(SM_EFUSE_USER_MAX,	0x82000033),
+		{ /* sentinel */ },
+	},
+};
+
+static u32 meson_sm_get_cmd(const struct meson_sm_chip *chip, unsigned int cmd_index)
+{
+	unsigned int i;
+
+	for (i = 0; chip->cmd[i].smc_id; i++)
+		if (chip->cmd[i].index == cmd_index)
+			return chip->cmd[i].smc_id;
+
+	return 0;
+}
+
+static u32 __meson_sm_call(u32 cmd, u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(cmd, arg0, arg1, arg2, arg3, arg4, 0, 0, &res);
+	return res.a0;
+}
+
+u32 meson_sm_call(struct meson_sm_firmware *fw, unsigned int cmd_index,
+		  u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+{
+	u32 cmd;
+
+	if (!fw)
+		return -EINVAL;
+
+	cmd = meson_sm_get_cmd(fw->chip, cmd_index);
+	if (!cmd)
+		return -EINVAL;
+
+	return __meson_sm_call(cmd, arg0, arg1, arg2, arg3, arg4);
+}
+EXPORT_SYMBOL(meson_sm_call);
+
+u32 meson_sm_call_read(struct meson_sm_firmware *fw, void *buffer,
+		       unsigned int cmd_index, u32 arg0, u32 arg1,
+		       u32 arg2, u32 arg3, u32 arg4)
+{
+	u32 size;
+
+	if (!fw->chip->cmd_shmem_out_base)
+		return -EINVAL;
+
+	size = meson_sm_call(fw, cmd_index, arg0, arg1, arg2, arg3, arg4);
+	if (size <= 0 || size > fw->chip->shmem_size)
+		return -EINVAL;
+
+	memcpy(buffer, fw->sm_shmem_out_base, size);
+
+	return size;
+}
+EXPORT_SYMBOL(meson_sm_call_read);
+
+u32 meson_sm_call_write(struct meson_sm_firmware *fw, void *buffer,
+			unsigned int b_size, unsigned int cmd_index,
+			u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+{
+	u32 size;
+
+	if (b_size > fw->chip->shmem_size)
+		return -EINVAL;
+
+	if (!fw->chip->cmd_shmem_in_base)
+		return -EINVAL;
+
+	memcpy(fw->sm_shmem_in_base, buffer, b_size);
+
+	size = meson_sm_call(fw, cmd_index, arg0, arg1, arg2, arg3, arg4);
+	if (size <= 0)
+		return -EINVAL;
+
+	return size;
+}
+EXPORT_SYMBOL(meson_sm_call_write);
+
+static void __iomem *meson_sm_map_shmem(u32 cmd_shmem, unsigned int size)
+{
+	u32 sm_phy_base;
+
+	sm_phy_base = __meson_sm_call(cmd_shmem, 0, 0, 0, 0, 0);
+	if (!sm_phy_base)
+		return 0;
+
+	return ioremap_cache(sm_phy_base, size);
+}
+
+static int meson_sm_probe(struct platform_device *pdev)
+{
+	const struct meson_sm_chip *chip;
+	struct meson_sm_firmware *fw;
+
+	fw = devm_kzalloc(&pdev->dev, sizeof(*fw), GFP_KERNEL);
+	if (!fw)
+		return -ENOMEM;
+
+	fw->dev = &pdev->dev;
+
+	chip = of_device_get_match_data(fw->dev);
+	if (!chip) {
+		dev_err(fw->dev, "Unable to setup secure-monitor data\n");
+		return -ENODEV;
+	}
+
+	if (chip->cmd_shmem_in_base) {
+		fw->sm_shmem_in_base = meson_sm_map_shmem(chip->cmd_shmem_in_base,
+							  chip->shmem_size);
+		if (!fw->sm_shmem_in_base)
+			goto out;
+	}
+
+	if (chip->cmd_shmem_out_base) {
+		fw->sm_shmem_out_base = meson_sm_map_shmem(chip->cmd_shmem_out_base,
+							   chip->shmem_size);
+		if (!fw->sm_shmem_out_base)
+			goto out;
+	}
+
+	fw->chip = chip;
+	platform_set_drvdata(pdev, fw);
+
+	dev_info(fw->dev, "secure-monitor enabled\n");
+
+	return 0;
+
+out:
+	if (fw->sm_shmem_in_base)
+		iounmap(fw->sm_shmem_in_base);
+
+	return -EINVAL;
+}
+
+struct meson_sm_firmware *meson_sm_get_fw(struct device_node *firmware_node)
+{
+	struct platform_device *pdev = of_find_device_by_node(firmware_node);
+
+	/*
+	 * Returns NULL is the firmware device is not ready.
+	 */
+	if (!pdev)
+		return NULL;
+
+	return platform_get_drvdata(pdev);
+}
+EXPORT_SYMBOL(meson_sm_get_fw);
+
+static const struct of_device_id meson_sm_ids[] = {
+	{ .compatible = "amlogic,meson-gxbb-sm", .data = &gxbb_chip },
+	{ /* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, meson_sm_ids);
+
+static struct platform_driver meson_sm_platform_driver = {
+	.probe	= meson_sm_probe,
+	.driver	= {
+		.name		= "secure-monitor",
+		.of_match_table	= meson_sm_ids,
+	},
+};
+module_platform_driver(meson_sm_platform_driver);
+
+MODULE_AUTHOR("Carlo Caione <carlo@endlessm.com>");
+MODULE_DESCRIPTION("Amlogic secure monitor driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/firmware/meson/meson_sm.h b/include/linux/firmware/meson/meson_sm.h
new file mode 100644
index 0000000..f653916
--- /dev/null
+++ b/include/linux/firmware/meson/meson_sm.h
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2016 Endless Mobile, Inc.
+ * Author: Carlo Caione <carlo@endlessm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _MESON_SM_FW_H_
+#define _MESON_SM_FW_H_
+
+#define SM_EFUSE_READ		0
+#define SM_EFUSE_WRITE		1
+#define SM_EFUSE_USER_MAX	2
+
+struct meson_sm_firmware;
+
+u32 meson_sm_call(struct meson_sm_firmware *fw, unsigned int cmd_index,
+		  u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4);
+u32 meson_sm_call_write(struct meson_sm_firmware *fw, void *buffer,
+			unsigned int b_size, unsigned int cmd_index,
+			u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4);
+u32 meson_sm_call_read(struct meson_sm_firmware *fw, void *buffer,
+		       unsigned int cmd_index, u32 arg0, u32 arg1,
+		       u32 arg2, u32 arg3, u32 arg4);
+struct meson_sm_firmware *meson_sm_get_fw(struct device_node *firmware_node);
+
+#endif /* _MESON_SM_FW_H_ */
-- 
2.7.4

[PATCH v5 2/3] documentation: Add secure monitor binding documentation

[Carlo Caione]

From: Carlo Caione <carlo@endlessm.com>

Add the binding documentation for the Amlogic secure monitor driver.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
---
 .../bindings/firmware/meson/meson_sm.txt           | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/firmware/meson/meson_sm.txt

diff --git a/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
new file mode 100644
index 0000000..6f0b5bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
@@ -0,0 +1,33 @@
+* Amlogic Secure Monitor
+
+In the Amlogic SoCs the Secure Monitor code is used to provide access to the
+NVMEM, enable JTAG, set USB boot, etc...
+
+Required properties for the secure monitor node:
+- compatible: Should be "amlogic,meson-gxbb-sm"
+
+Example:
+
+	firmware {
+		compatible = "simple-bus";
+
+		sm: secure-monitor {
+			compatible = "amlogic,meson-gxbb-sm";
+		};
+	};
+
+Example of the node using the secure monitor:
+
+	#include <dt-bindings/firmware/meson-sm.h>
+
+	...
+
+	efuse: efuse {
+		compatible = "amlogic,meson-gxbb-efuse";
+		secure-monitor = <&sm>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		...
+	};
+
-- 
2.7.4

[PATCH v5 3/3] ARM64: dts: amlogic: gxbb: Enable secure monitor

[Carlo Caione]

From: Carlo Caione <carlo@endlessm.com>

Add the secure monitor node in the Amlogic Meson GXBB DTSI file to
enable it.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
---
 arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
index 76b3b6d..a453bbf 100644
--- a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
+++ b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
@@ -98,6 +98,14 @@
 		method = "smc";
 	};
 
+	firmware {
+		compatible = "simple-bus";
+
+		sm: secure-monitor {
+			compatible = "amlogic,meson-gxbb-sm";
+		};
+	};
+
 	timer {
 		compatible = "arm,armv8-timer";
 		interrupts = <GIC_PPI 13
-- 
2.7.4

[PATCH v5 1/3] firmware: Amlogic: Add secure monitor driver

[Carlo Caione]

On 29/05/16 12:27, Ben Dooks wrote:

[...]
> > +u32 meson_sm_call_read(struct meson_sm_firmware *fw, void *buffer,
> > +                      unsigned int cmd_index, u32 arg0, u32 arg1,
> > +                      u32 arg2, u32 arg3, u32 arg4)
> > +{
> > +       u32 size;
> > +
> > +       if (!fw->chip->cmd_shmem_out_base)
> > +               return -EINVAL;
> > +
> > +       size = meson_sm_call(fw, cmd_index, arg0, arg1, arg2, arg3, arg4);
> > +       if (size <= 0 || size > fw->chip->shmem_size)
> > +               return -EINVAL;
> > +
> u32 cannot be less than 0

Ouch. Definitely overlooked that. Fix coming.

[...]
> > +static int meson_sm_probe(struct platform_device *pdev)
> > +{
> > +       const struct meson_sm_chip *chip;
> > +       struct meson_sm_firmware *fw;
> > +
> > +       fw = devm_kzalloc(&pdev->dev, sizeof(*fw), GFP_KERNEL);
> > +       if (!fw)
> > +               return -ENOMEM;
> > +
> > +       fw->dev = &pdev->dev;
> > +
> > +       chip = of_device_get_match_data(fw->dev);
> > +       if (!chip) {
> > +               dev_err(fw->dev, "Unable to setup secure-monitor data\n");
> > +               return -ENODEV;
> > +       }
> -ENODEV not best return here. Return -EINVAL better. -ENODEV won't get
> reported by device layer

Ok

[...]
> > +               if (!fw->sm_shmem_in_base)
> > +                       goto out;
> > +       }
>   Maybe use WarnOn here

Alright.

Cheers,

-- 
Carlo Caione

[PATCH v5 2/3] documentation: Add secure monitor binding documentation

[Rob Herring]

On Sun, May 29, 2016 at 01:12:02PM +0200, Carlo Caione wrote:
> From: Carlo Caione <carlo@endlessm.com>
> 
> Add the binding documentation for the Amlogic secure monitor driver.
> 
> Signed-off-by: Carlo Caione <carlo@endlessm.com>
> ---
>  .../bindings/firmware/meson/meson_sm.txt           | 33 ++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
> 
> diff --git a/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
> new file mode 100644
> index 0000000..6f0b5bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
> @@ -0,0 +1,33 @@
> +* Amlogic Secure Monitor
> +
> +In the Amlogic SoCs the Secure Monitor code is used to provide access to the
> +NVMEM, enable JTAG, set USB boot, etc...
> +
> +Required properties for the secure monitor node:
> +- compatible: Should be "amlogic,meson-gxbb-sm"
> +
> +Example:
> +
> +	firmware {
> +		compatible = "simple-bus";

Drop this. Sorry, but no abusing simple-bus to get automagic creation of 
your platform device.

> +
> +		sm: secure-monitor {
> +			compatible = "amlogic,meson-gxbb-sm";
> +		};
> +	};
> +
> +Example of the node using the secure monitor:
> +
> +	#include <dt-bindings/firmware/meson-sm.h>
> +
> +	...
> +
> +	efuse: efuse {
> +		compatible = "amlogic,meson-gxbb-efuse";
> +		secure-monitor = <&sm>;

Why do you need this? Given there can only be one node, just use 
of_find_compatible_node();

> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +
> +		...
> +	};
> +
> -- 
> 2.7.4
> 

[PATCH v5 2/3] documentation: Add secure monitor binding documentation

[Carlo Caione]

On 02/06/16 12:14, Rob Herring wrote:
> On Sun, May 29, 2016 at 01:12:02PM +0200, Carlo Caione wrote:
> > From: Carlo Caione <carlo@endlessm.com>
> > 
> > Add the binding documentation for the Amlogic secure monitor driver.
> > 
> > Signed-off-by: Carlo Caione <carlo@endlessm.com>
> > ---
> >  .../bindings/firmware/meson/meson_sm.txt           | 33 ++++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
> > new file mode 100644
> > index 0000000..6f0b5bc
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
> > @@ -0,0 +1,33 @@
> > +* Amlogic Secure Monitor
> > +
> > +In the Amlogic SoCs the Secure Monitor code is used to provide access to the
> > +NVMEM, enable JTAG, set USB boot, etc...
> > +
> > +Required properties for the secure monitor node:
> > +- compatible: Should be "amlogic,meson-gxbb-sm"
> > +
> > +Example:
> > +
> > +	firmware {
> > +		compatible = "simple-bus";
> 
> Drop this. Sorry, but no abusing simple-bus to get automagic creation of 
> your platform device.

Sounds reasonable. I can hook this up to some *_initcall. What about
introducing a new FIRMWARE_OF_DECLARE() ?

Cheers,

-- 
Carlo Caione

[PATCH v5 2/3] documentation: Add secure monitor binding documentation

[Rob Herring]

On Fri, Jun 3, 2016 at 4:25 AM, Carlo Caione <carlo@caione.org> wrote:
> On 02/06/16 12:14, Rob Herring wrote:
>> On Sun, May 29, 2016 at 01:12:02PM +0200, Carlo Caione wrote:
>> > From: Carlo Caione <carlo@endlessm.com>
>> >
>> > Add the binding documentation for the Amlogic secure monitor driver.
>> >
>> > Signed-off-by: Carlo Caione <carlo@endlessm.com>
>> > ---
>> >  .../bindings/firmware/meson/meson_sm.txt           | 33 ++++++++++++++++++++++
>> >  1 file changed, 33 insertions(+)
>> >  create mode 100644 Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
>> >
>> > diff --git a/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
>> > new file mode 100644
>> > index 0000000..6f0b5bc
>> > --- /dev/null
>> > +++ b/Documentation/devicetree/bindings/firmware/meson/meson_sm.txt
>> > @@ -0,0 +1,33 @@
>> > +* Amlogic Secure Monitor
>> > +
>> > +In the Amlogic SoCs the Secure Monitor code is used to provide access to the
>> > +NVMEM, enable JTAG, set USB boot, etc...
>> > +
>> > +Required properties for the secure monitor node:
>> > +- compatible: Should be "amlogic,meson-gxbb-sm"
>> > +
>> > +Example:
>> > +
>> > +   firmware {
>> > +           compatible = "simple-bus";
>>
>> Drop this. Sorry, but no abusing simple-bus to get automagic creation of
>> your platform device.
>
> Sounds reasonable. I can hook this up to some *_initcall. What about
> introducing a new FIRMWARE_OF_DECLARE() ?

Please don't add FIRMWARE_OF_DECLARE unless it needs to be early.

Rob

[PATCH v5 2/3] documentation: Add secure monitor binding documentation

[Carlo Caione]

On 02/06/16 12:14, Rob Herring wrote:
> On Sun, May 29, 2016 at 01:12:02PM +0200, Carlo Caione wrote:

[...]
> > +Example of the node using the secure monitor:
> > +
> > +	#include <dt-bindings/firmware/meson-sm.h>
> > +
> > +	...
> > +
> > +	efuse: efuse {
> > +		compatible = "amlogic,meson-gxbb-efuse";
> > +		secure-monitor = <&sm>;
> 
> Why do you need this? Given there can only be one node, just use 
> of_find_compatible_node();

of_find_compatible_node() in the driver works fine if we have only one
possible compatible property for the secure-monitor node. In this case
we have a different compatible property for each SoC (GXBB in this case)
so I think having the phandle in the DT is still the best thing to do.

Any thought on this Rob?

-- 
Carlo Caione