[PATCH 0/5] Exynos850 APM-to-AP mailbox support

[PATCH 0/5] Exynos850 APM-to-AP mailbox support

[Alexey Klimov]

Hi all,

This patch series introduces support for the APM-to-AP mailbox on the 
Exynos850 SoC. This mailbox is required for communicating with the APM 
co-processor using ACPM.

The Exynos850 mailbox operates similarly to the existing gs101 
implementation, but the register offsets and IRQ mask bits differ. 
This series abstracts these differences into platform-specific data 
structures matched via the device tree.

Also, it requires APM-to-AP mailbox clock in CMU_APM block.

In theory this can be split into two series with correct dependecies:
device tree node requires clock changes to be merged. The suggestion
is to let this go through Samsung SoC tree with corresponding acks
if it is okay.

Will be great if it can be tested on gs101 to make sure that I didn't
break anything, I don't have dev gs101 devices.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
Alexey Klimov (5):
      dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock
      clk: samsung: exynos850: Add APM-to-AP mailbox clock
      dt-bindings: mailbox: google,gs101-mbox: Add samsung,exynos850-mbox
      mailbox: exynos: Add support for Exynos850 mailbox
      arm64: dts: exynos850: Add ap2apm mailbox

 .../bindings/mailbox/google,gs101-mbox.yaml        |  4 +-
 arch/arm64/boot/dts/exynos/exynos850.dtsi          |  9 +++
 drivers/clk/samsung/clk-exynos850.c                |  7 ++-
 drivers/mailbox/exynos-mailbox.c                   | 65 +++++++++++++++++++++-
 include/dt-bindings/clock/exynos850.h              |  1 +
 5 files changed, 81 insertions(+), 5 deletions(-)
---
base-commit: 785f0eb2f85decbe7c1ef9ae922931f0194ffc2e
change-id: 20260320-exynos850-ap2apm-mailbox-cff0c8d69898

Best regards,
-- 
Alexey Klimov <alexey.klimov@linaro.org>

[PATCH 1/5] dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock

[Alexey Klimov]

Add a constant for APM-to-AP mailbox clock. This clock is needed
to access this mailbox registers.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 include/dt-bindings/clock/exynos850.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/dt-bindings/clock/exynos850.h b/include/dt-bindings/clock/exynos850.h
index 80dacda57229..95285589615a 100644
--- a/include/dt-bindings/clock/exynos850.h
+++ b/include/dt-bindings/clock/exynos850.h
@@ -126,6 +126,7 @@
 #define CLK_GOUT_GPIO_ALIVE_PCLK	22
 #define CLK_GOUT_PMU_ALIVE_PCLK		23
 #define CLK_GOUT_SYSREG_APM_PCLK	24
+#define CLK_GOUT_MAILBOX_APM_AP_PCLK	25
 
 /* CMU_AUD */
 #define CLK_DOUT_AUD_AUDIF		1

-- 
2.51.0

[PATCH 2/5] clk: samsung: exynos850: Add APM-to-AP mailbox clock

[Alexey Klimov]

Add APM mailbox clock for communicating between APM and main application
CPUs in CMU_APM unit. This clock is needed to access this mailbox
registers. This mailbox is used for ACPM communication between kernel
and APM co-processor.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 drivers/clk/samsung/clk-exynos850.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/samsung/clk-exynos850.c b/drivers/clk/samsung/clk-exynos850.c
index 56f27697c76b..eb9c80b60225 100644
--- a/drivers/clk/samsung/clk-exynos850.c
+++ b/drivers/clk/samsung/clk-exynos850.c
@@ -19,7 +19,7 @@
 
 /* NOTE: Must be equal to the last clock ID increased by one */
 #define CLKS_NR_TOP			(CLK_DOUT_CPUCL1_SWITCH + 1)
-#define CLKS_NR_APM			(CLK_GOUT_SYSREG_APM_PCLK + 1)
+#define CLKS_NR_APM			(CLK_GOUT_MAILBOX_APM_AP_PCLK + 1)
 #define CLKS_NR_AUD			(CLK_GOUT_AUD_CMU_AUD_PCLK + 1)
 #define CLKS_NR_CMGP			(CLK_GOUT_SYSREG_CMGP_PCLK + 1)
 #define CLKS_NR_CPUCL0			(CLK_CLUSTER0_SCLK + 1)
@@ -604,6 +604,7 @@ CLK_OF_DECLARE(exynos850_cmu_top, "samsung,exynos850-cmu-top",
 #define CLK_CON_GAT_GOUT_APM_APBIF_TOP_RTC_PCLK		0x2028
 #define CLK_CON_GAT_GOUT_APM_I3C_APM_PMIC_I_PCLK	0x2034
 #define CLK_CON_GAT_GOUT_APM_I3C_APM_PMIC_I_SCLK	0x2038
+#define CLK_CON_GAT_GOUT_APM_MAILBOX_APM_AP_PCLK	0x2060
 #define CLK_CON_GAT_GOUT_APM_SPEEDY_APM_PCLK		0x20bc
 #define CLK_CON_GAT_GOUT_APM_SYSREG_APM_PCLK		0x20c0
 
@@ -628,6 +629,7 @@ static const unsigned long apm_clk_regs[] __initconst = {
 	CLK_CON_GAT_GOUT_APM_I3C_APM_PMIC_I_SCLK,
 	CLK_CON_GAT_GOUT_APM_SPEEDY_APM_PCLK,
 	CLK_CON_GAT_GOUT_APM_SYSREG_APM_PCLK,
+	CLK_CON_GAT_GOUT_APM_MAILBOX_APM_AP_PCLK,
 };
 
 /* List of parent clocks for Muxes in CMU_APM */
@@ -698,6 +700,9 @@ static const struct samsung_gate_clock apm_gate_clks[] __initconst = {
 	     CLK_CON_GAT_GOUT_APM_APBIF_PMU_ALIVE_PCLK, 21, CLK_IS_CRITICAL, 0),
 	GATE(CLK_GOUT_SYSREG_APM_PCLK, "gout_sysreg_apm_pclk", "dout_apm_bus",
 	     CLK_CON_GAT_GOUT_APM_SYSREG_APM_PCLK, 21, 0, 0),
+	GATE(CLK_GOUT_MAILBOX_APM_AP_PCLK, "gout_mailbox_apm_ap_pclk",
+	     "dout_apm_func",
+	     CLK_CON_GAT_GOUT_APM_MAILBOX_APM_AP_PCLK, 21, 0, 0),
 };
 
 static const struct samsung_cmu_info apm_cmu_info __initconst = {

-- 
2.51.0

[PATCH 3/5] dt-bindings: mailbox: google,gs101-mbox: Add samsung,exynos850-mbox

[Alexey Klimov]

Document support for a mailbox present on Exynos850-based platforms.
While at this, convert the compatibles selection to enum.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml b/Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml
index e249db4c1fbc..c109c1f7af24 100644
--- a/Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml
+++ b/Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml
@@ -20,7 +20,9 @@ description:
 
 properties:
   compatible:
-    const: google,gs101-mbox
+    enum:
+      - google,gs101-mbox
+      - samsung,exynos850-mbox
 
   reg:
     maxItems: 1

-- 
2.51.0

[PATCH 4/5] mailbox: exynos: Add support for Exynos850 mailbox

[Alexey Klimov]

Exynos850-based platforms support ACPM and has similar workflow
of communicating with ACPM via mailbox, however mailbox controller
registers are located at different offsets and writes/reads could be
different. To distinguish between such different behaviours,
the registers offsets for Exynos850 and the platform-specific data
structs are introduced and configuration is described in such structs
for gs101 and exynos850 based SoCs. Probe routine now selects the
corresponding platform-specific data via device_get_match_data().

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 drivers/mailbox/exynos-mailbox.c | 65 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 62 insertions(+), 3 deletions(-)

diff --git a/drivers/mailbox/exynos-mailbox.c b/drivers/mailbox/exynos-mailbox.c
index 5f2d3b81c1db..3727e1ff0fc2 100644
--- a/drivers/mailbox/exynos-mailbox.c
+++ b/drivers/mailbox/exynos-mailbox.c
@@ -31,14 +31,59 @@
 
 #define EXYNOS_MBOX_CHAN_COUNT		HWEIGHT32(EXYNOS_MBOX_INTGR1_MASK)
 
+#define EXYNOS850_MBOX_MCUCTRL		0x0	/* Mailbox Control Register		*/
+#define EXYNOS850_MBOX_INTGR0		0x8	/* Interrupt Generation Register 0	*/
+#define EXYNOS850_MBOX_INTCR0		0x0C	/* Interrupt Clear Register 0		*/
+#define EXYNOS850_MBOX_INTMR0		0x10	/* Interrupt Mask Register 0		*/
+#define EXYNOS850_MBOX_INTSR0		0x14	/* Interrupt Status Register 0		*/
+#define EXYNOS850_MBOX_INTMSR0		0x18	/* Interrupt Mask Status Register 0	*/
+#define EXYNOS850_MBOX_INTGR1		0x1C	/* Interrupt Generation Register 1	*/
+#define EXYNOS850_MBOX_INTMR1		0x24	/* Interrupt Mask Register 1		*/
+#define EXYNOS850_MBOX_INTSR1		0x28	/* Interrupt Status Register 1		*/
+#define EXYNOS850_MBOX_INTMSR1		0x2C	/* Interrupt Mask Status Register 1	*/
+#define EXYNOS850_MBOX_VERSION		0x70
+
+#define EXYNOS850_MBOX_INTMR1_MASK	GENMASK(15, 0)
+
+/**
+ * struct exynos_mbox_driver_data - platform-specific mailbox configuration.
+ * @irq_doorbell_offset:	offset to the IRQ generation register, doorbell
+ *				to APM co-processor.
+ * @irq_doorbell_shift:		shift to apply to the value written to IRQ
+ *				generation register.
+ * @irq_mask_offset:		offset to the IRQ mask register.
+ */
+struct exynos_mbox_driver_data {
+	u16 irq_doorbell_offset;
+	u16 irq_doorbell_shift;
+	u16 irq_mask_offset;
+	u16 irq_mask_value;
+};
+
 /**
  * struct exynos_mbox - driver's private data.
  * @regs:	mailbox registers base address.
  * @mbox:	pointer to the mailbox controller.
+ * @data:	pointer to driver platform-specific data.
  */
 struct exynos_mbox {
 	void __iomem *regs;
 	struct mbox_controller *mbox;
+	const struct exynos_mbox_driver_data *data;
+};
+
+static const struct exynos_mbox_driver_data exynos850_mbox_data = {
+	.irq_doorbell_offset = EXYNOS850_MBOX_INTGR0,
+	.irq_doorbell_shift = 16,
+	.irq_mask_offset = EXYNOS850_MBOX_INTMR1,
+	.irq_mask_value = EXYNOS850_MBOX_INTMR1_MASK,
+};
+
+static const struct exynos_mbox_driver_data exynos_gs101_mbox_data = {
+	.irq_doorbell_offset = EXYNOS_MBOX_INTGR1,
+	.irq_doorbell_shift = 0,
+	.irq_mask_offset = EXYNOS_MBOX_INTMR0,
+	.irq_mask_value = EXYNOS_MBOX_INTMR0_MASK,
 };
 
 static int exynos_mbox_send_data(struct mbox_chan *chan, void *data)
@@ -57,7 +102,8 @@ static int exynos_mbox_send_data(struct mbox_chan *chan, void *data)
 		return -EINVAL;
 	}
 
-	writel(BIT(msg->chan_id), exynos_mbox->regs + EXYNOS_MBOX_INTGR1);
+	writel(BIT(msg->chan_id) << exynos_mbox->data->irq_doorbell_shift,
+	       exynos_mbox->regs + exynos_mbox->data->irq_doorbell_offset);
 
 	return 0;
 }
@@ -87,13 +133,21 @@ static struct mbox_chan *exynos_mbox_of_xlate(struct mbox_controller *mbox,
 }
 
 static const struct of_device_id exynos_mbox_match[] = {
-	{ .compatible = "google,gs101-mbox" },
+	{
+		.compatible = "google,gs101-mbox",
+		.data = &exynos_gs101_mbox_data
+	},
+	{
+		.compatible = "samsung,exynos850-mbox",
+		.data = &exynos850_mbox_data
+	},
 	{},
 };
 MODULE_DEVICE_TABLE(of, exynos_mbox_match);
 
 static int exynos_mbox_probe(struct platform_device *pdev)
 {
+	const struct exynos_mbox_driver_data *data;
 	struct device *dev = &pdev->dev;
 	struct exynos_mbox *exynos_mbox;
 	struct mbox_controller *mbox;
@@ -123,6 +177,11 @@ static int exynos_mbox_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(pclk),
 				     "Failed to enable clock.\n");
 
+	data = device_get_match_data(&pdev->dev);
+	if (!data)
+		return -ENODEV;
+
+	exynos_mbox->data = data;
 	mbox->num_chans = EXYNOS_MBOX_CHAN_COUNT;
 	mbox->chans = chans;
 	mbox->dev = dev;
@@ -137,7 +196,7 @@ static int exynos_mbox_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, exynos_mbox);
 
 	/* Mask out all interrupts. We support just polling channels for now. */
-	writel(EXYNOS_MBOX_INTMR0_MASK, exynos_mbox->regs + EXYNOS_MBOX_INTMR0);
+	writel(data->irq_mask_value, exynos_mbox->regs + data->irq_mask_offset);
 
 	return devm_mbox_controller_register(dev, mbox);
 }

-- 
2.51.0

[PATCH 5/5] arm64: dts: exynos850: Add ap2apm mailbox

[Alexey Klimov]

Add mailbox node that describes AP-to-APM mailbox, that can be
used for communicating with APM co-processor on Exynos850 SoCs.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 arch/arm64/boot/dts/exynos/exynos850.dtsi | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm64/boot/dts/exynos/exynos850.dtsi b/arch/arm64/boot/dts/exynos/exynos850.dtsi
index cb55015c8dce..fcb665ccc7ae 100644
--- a/arch/arm64/boot/dts/exynos/exynos850.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos850.dtsi
@@ -298,6 +298,15 @@ cmu_apm: clock-controller@11800000 {
 			clock-names = "oscclk", "dout_clkcmu_apm_bus";
 		};
 
+		ap2apm_mailbox: mailbox@11900000 {
+			compatible = "samsung,exynos850-mbox";
+			reg = <0x11900000 0x1000>;
+			clocks = <&cmu_apm CLK_GOUT_MAILBOX_APM_AP_PCLK>;
+			clock-names = "pclk";
+			interrupts = <GIC_SPI 49 IRQ_TYPE_LEVEL_HIGH>;
+			#mbox-cells = <0>;
+		};
+
 		cmu_cmgp: clock-controller@11c00000 {
 			compatible = "samsung,exynos850-cmu-cmgp";
 			reg = <0x11c00000 0x8000>;

-- 
2.51.0

Re: [PATCH 0/5] Exynos850 APM-to-AP mailbox support

[Krzysztof Kozlowski]

On Fri, Mar 20, 2026 at 09:15:12PM +0000, Alexey Klimov wrote:
> Hi all,
> 
> This patch series introduces support for the APM-to-AP mailbox on the 
> Exynos850 SoC. This mailbox is required for communicating with the APM 
> co-processor using ACPM.
> 
> The Exynos850 mailbox operates similarly to the existing gs101 
> implementation, but the register offsets and IRQ mask bits differ. 
> This series abstracts these differences into platform-specific data 
> structures matched via the device tree.
> 
> Also, it requires APM-to-AP mailbox clock in CMU_APM block.
> 
> In theory this can be split into two series with correct dependecies:
> device tree node requires clock changes to be merged. The suggestion
> is to let this go through Samsung SoC tree with corresponding acks
> if it is okay.

I don't understand why this cannot be split into two seris
*practically*. What is exactly the dependency between mailbox and DTS,
that it had to be combined here?


Best regards,
Krzysztof

Re: [PATCH 3/5] dt-bindings: mailbox: google,gs101-mbox: Add samsung,exynos850-mbox

[Krzysztof Kozlowski]

On Fri, Mar 20, 2026 at 09:15:15PM +0000, Alexey Klimov wrote:
> Document support for a mailbox present on Exynos850-based platforms.

Here you explain the hardware, e.g. that they are not compatible.

> While at this, convert the compatibles selection to enum.

This part is redundant and obvious, can you do it without any sort of
conversion? Not really.

Best regards,
Krzysztof

Re: [PATCH 4/5] mailbox: exynos: Add support for Exynos850 mailbox

[kernel test robot]

Hi Alexey,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 785f0eb2f85decbe7c1ef9ae922931f0194ffc2e]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexey-Klimov/dt-bindings-clock-exynos850-Add-APM_AP-MAILBOX-clock/20260322-085441
base:   785f0eb2f85decbe7c1ef9ae922931f0194ffc2e
patch link:    https://lore.kernel.org/r/20260320-exynos850-ap2apm-mailbox-v1-4-983eb3f296fc%40linaro.org
patch subject: [PATCH 4/5] mailbox: exynos: Add support for Exynos850 mailbox
config: x86_64-buildonly-randconfig-004-20260322 (https://download.01.org/0day-ci/archive/20260322/202603222239.JTuBxs7K-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260322/202603222239.JTuBxs7K-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603222239.JTuBxs7K-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/mailbox/exynos-mailbox.c:60 struct member 'irq_mask_value' not described in 'exynos_mbox_driver_data'
>> Warning: drivers/mailbox/exynos-mailbox.c:60 struct member 'irq_mask_value' not described in 'exynos_mbox_driver_data'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 4/5] mailbox: exynos: Add support for Exynos850 mailbox

[Alexey Klimov]

On Sun Mar 22, 2026 at 2:15 PM GMT, kernel test robot wrote:
> Hi Alexey,
> kernel test robot noticed the following build warnings:
[..]
>>> Warning: drivers/mailbox/exynos-mailbox.c:60 struct member 'irq_mask_value' not described in 'exynos_mbox_driver_data'
>>> Warning: drivers/mailbox/exynos-mailbox.c:60 struct member 'irq_mask_value' not described in 'exynos_mbox_driver_data'

Thanks, I'll correct it in the next version. The warning is a bit vague itself
though, the problem is comment that describes the mentioned struct.

Thanks,
Alexey

Re: (subset) [PATCH 1/5] dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock

[Krzysztof Kozlowski]

On Fri, 20 Mar 2026 21:15:13 +0000, Alexey Klimov wrote:
> Add a constant for APM-to-AP mailbox clock. This clock is needed
> to access this mailbox registers.

Applied, thanks!

[1/5] dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock
      https://git.kernel.org/krzk/linux/c/bf9462c82721e42f49e4a62efe96ef7b41a5e42e

Best regards,
-- 
Krzysztof Kozlowski <krzk@kernel.org>

Re: (subset) [PATCH 2/5] clk: samsung: exynos850: Add APM-to-AP mailbox clock

[Krzysztof Kozlowski]

On Fri, 20 Mar 2026 21:15:14 +0000, Alexey Klimov wrote:
> Add APM mailbox clock for communicating between APM and main application
> CPUs in CMU_APM unit. This clock is needed to access this mailbox
> registers. This mailbox is used for ACPM communication between kernel
> and APM co-processor.

Applied, thanks!

[2/5] clk: samsung: exynos850: Add APM-to-AP mailbox clock
      https://git.kernel.org/krzk/linux/c/e57c36bc1a3e459239ead492ebce731a88a264b1

Best regards,
-- 
Krzysztof Kozlowski <krzk@kernel.org>