[PATCH 3/3] xen/arm: add i.MX8M platform support

[Wig Cheng <onlywig@xxxxxxxxx>]

Add platform glue for the NXP i.MX8M family (i.MX8MP/MQ/MM/MN).

When Linux is used as dom0 a number of drivers make SiP SMC calls into
TF-A to manage hardware: GPC power domains, DDR frequency scaling, SRC
(M-core remoteproc), SoC info, NoC QoS and BBSM tamper status.  There
is no public specification for these calls; the function IDs are taken
from the upstream and vendor kernels.

Forward this reviewed set of calls from the hardware domain, following
the whitelist model of the i.MX8QM platform.  CPU frequency scaling is
denied because the hardware domain cannot make an informed decision,
and any unknown function ID is rejected.

Signed-off-by: Wig Cheng <onlywig@xxxxxxxxx>
---
 xen/arch/arm/platforms/Makefile |   1 +
 xen/arch/arm/platforms/imx8m.c  | 116 ++++++++++++++++++++++++++++++++
 2 files changed, 117 insertions(+)
 create mode 100644 xen/arch/arm/platforms/imx8m.c

diff --git a/xen/arch/arm/platforms/Makefile b/xen/arch/arm/platforms/Makefile
index bec6e55d1f..cdf936c50d 100644
--- a/xen/arch/arm/platforms/Makefile
+++ b/xen/arch/arm/platforms/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_ALL_PLAT)   += sunxi.o
 obj-$(CONFIG_ALL64_PLAT) += thunderx.o
 obj-$(CONFIG_ALL64_PLAT) += xgene-storm.o
 obj-$(CONFIG_ALL64_PLAT) += brcm-raspberry-pi.o
+obj-$(CONFIG_ALL64_PLAT) += imx8m.o
 obj-$(CONFIG_ALL64_PLAT) += imx8qm.o
 obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp.o
 obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp-eemi.o
diff --git a/xen/arch/arm/platforms/imx8m.c b/xen/arch/arm/platforms/imx8m.c
new file mode 100644
index 0000000000..dc49e754ee
--- /dev/null
+++ b/xen/arch/arm/platforms/imx8m.c
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * xen/arch/arm/platforms/imx8m.c
+ *
+ * i.MX 8M family setup
+ *
+ * Copyright 2026 Open-EP (E-Paper) Community
+ */
+
+#include <xen/sched.h>
+#include <asm/platform.h>
+#include <asm/smccc.h>
+
+static const char * const imx8m_dt_compat[] __initconst =
+{
+    "fsl,imx8mp",
+    "fsl,imx8mq",
+    "fsl,imx8mm",
+    "fsl,imx8mn",
+    NULL
+};
+
+/*
+ * SiP SMC function IDs used by the i.MX8M Linux drivers.  There is no
+ * public specification for these; the IDs and names are extracted from
+ * the upstream and vendor kernels (see drivers/soc/imx, drivers/devfreq,
+ * drivers/remoteproc, drivers/firmware/imx).
+ */
+#define IMX_SIP_GPC         0xC2000000  /* GPC power-domain control */
+#define IMX_SIP_CPUFREQ     0xC2000001
+#define IMX_SIP_DDR_DVFS    0xC2000004  /* DRAM frequency scaling */
+#define IMX_SIP_SRC         0xC2000005  /* SRC: M-core remoteproc start/stop */
+#define IMX_SIP_GET_SOC_INFO 0xC2000006
+#define IMX_SIP_NOC         0xC2000008  /* NoC QoS priority setup */
+#define IMX_SIP_BBSM        0xC200000D  /* BBSM tamper status */
+
+static bool imx8m_smc(struct cpu_user_regs *regs)
+{
+    uint32_t function_id = get_user_reg(regs, 0);
+    struct arm_smccc_res res;
+
+    if ( !cpus_have_const_cap(ARM_SMCCC_1_1) )
+    {
+        printk_once(XENLOG_WARNING
+                    "imx8m: smc: no SMCCC 1.1 support. Disabling firmware 
calls\n");
+
+        return false;
+    }
+
+    /* Only the hardware domain may use the SiP calls */
+    if ( !is_hardware_domain(current->domain) )
+    {
+        gprintk(XENLOG_WARNING, "imx8m: smc: No access\n");
+        return false;
+    }
+
+    switch ( function_id )
+    {
+    /*
+     * All of these manage hardware that belongs to the hardware domain
+     * (power domains, DRAM controller, M-core, NoC, secure RTC) or are
+     * read-only queries.  Forward them.
+     */
+    case IMX_SIP_GPC:
+    case IMX_SIP_DDR_DVFS:
+    case IMX_SIP_SRC:
+    case IMX_SIP_GET_SOC_INFO:
+    case IMX_SIP_NOC:
+    case IMX_SIP_BBSM:
+        break;
+
+    /*
+     * CPU frequency scaling: the hardware domain does not see the whole
+     * system and cannot make an informed decision, so deny it (matches
+     * the i.MX8QM platform).
+     */
+    case IMX_SIP_CPUFREQ:
+        return false;
+
+    default:
+        gprintk(XENLOG_WARNING, "imx8m: smc: Unknown function id %x\n",
+                function_id);
+        return false;
+    }
+
+    arm_smccc_1_1_smc(function_id,
+                      get_user_reg(regs, 1),
+                      get_user_reg(regs, 2),
+                      get_user_reg(regs, 3),
+                      get_user_reg(regs, 4),
+                      get_user_reg(regs, 5),
+                      get_user_reg(regs, 6),
+                      get_user_reg(regs, 7),
+                      &res);
+
+    set_user_reg(regs, 0, res.a0);
+    set_user_reg(regs, 1, res.a1);
+    set_user_reg(regs, 2, res.a2);
+    set_user_reg(regs, 3, res.a3);
+
+    return true;
+}
+
+PLATFORM_START(imx8m, "i.MX 8M")
+    .compatible = imx8m_dt_compat,
+    .smc = imx8m_smc,
+PLATFORM_END
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.43.0