xen/arm: Add imx8q{m,x} platform glue

When using Linux for dom0 there are a bunch of drivers that need to do SMC
SIP calls into the firmware to enable certain hardware bits like the
watchdog.

Provide a basic platform glue that implements the needed SMC forwarding.

The format of these calls are as follows:
 - reg 0: function ID
 - reg 1: subfunction ID (when there's a subfunction)
 remaining regs: args

For now we only allow Dom0 to make these calls as they are all managing
hardware. There is no specification for these SIP calls, the IDs and names
have been extracted from the upstream linux kernel and the vendor kernel.

We can reject CPUFREQ because Dom0 cannot make an informed decision
regarding CPU frequency scaling, WAKEUP_SRC is to wake up from suspend,
which Xen doesn't support at this time.

This leaves the TIME SIP, OTP SIPs which for now are allowed to Dom0.

NOTE: This code is based on code found in NXP Xen tree located here:
https://github.com/nxp-imx/imx-xen/blob/lf-5.10.y_4.13/xen/arch/arm/platforms/imx8qm.c

Signed-off-by: Peng Fan <peng.fan@nxp.com>
[jernberg: Add SIP call filtering]
Signed-off-by: John Ernberg <john.ernberg@actia.se>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>
[stefano: commit message improvement]
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>

xen/arch/arm/platforms/Makefile

@@ -9,5 +9,6 @@ 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-$(CONFIG_ALL64_PLAT) += imx8qm.o
 obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp.o
 obj-$(CONFIG_MPSOC_PLATFORM)  += xilinx-zynqmp-eemi.o

xen/arch/arm/platforms/imx8qm.c

@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * xen/arch/arm/platforms/imx8qm.c
+ *
+ * i.MX 8QM setup
+ *
+ * Copyright (c) 2016 Freescale Inc.
+ * Copyright 2018-2019 NXP
+ *
+ *
+ * Peng Fan <peng.fan@nxp.com>
+ */
+
+#include <xen/sched.h>
+#include <asm/platform.h>
+#include <asm/smccc.h>
+
+static const char * const imx8qm_dt_compat[] __initconst =
+{
+    "fsl,imx8qm",
+    "fsl,imx8qxp",
+    NULL
+};
+
+#define IMX_SIP_FID(fid) \
+    ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+                       ARM_SMCCC_CONV_64, \
+                       ARM_SMCCC_OWNER_SIP, \
+                       (fid))
+
+#define IMX_SIP_F_CPUFREQ        0x1
+#define IMX_SIP_F_TIME           0x2
+#define IMX_SIP_F_WAKEUP_SRC     0x9
+#define IMX_SIP_F_OTP_WRITE      0xB
+
+#define IMX_SIP_TIME_SF_RTC_SET_TIME     0x00
+#define IMX_SIP_TIME_SF_WDOG_START       0x01
+#define IMX_SIP_TIME_SF_WDOG_STOP        0x02
+#define IMX_SIP_TIME_SF_WDOG_SET_ACT     0x03
+#define IMX_SIP_TIME_SF_WDOG_PING        0x04
+#define IMX_SIP_TIME_SF_WDOG_SET_TIMEOUT 0x05
+#define IMX_SIP_TIME_SF_WDOG_GET_STAT    0x06
+#define IMX_SIP_TIME_SF_WDOG_SET_PRETIME 0x07
+
+static bool imx8qm_is_sip_time_call_ok(uint32_t subfunction_id)
+{
+    switch ( subfunction_id )
+    {
+    case IMX_SIP_TIME_SF_RTC_SET_TIME:
+        return true;
+    case IMX_SIP_TIME_SF_WDOG_START:
+    case IMX_SIP_TIME_SF_WDOG_STOP:
+    case IMX_SIP_TIME_SF_WDOG_SET_ACT:
+    case IMX_SIP_TIME_SF_WDOG_PING:
+    case IMX_SIP_TIME_SF_WDOG_SET_TIMEOUT:
+    case IMX_SIP_TIME_SF_WDOG_GET_STAT:
+    case IMX_SIP_TIME_SF_WDOG_SET_PRETIME:
+        return true;
+    default:
+        gprintk(XENLOG_WARNING, "imx8qm: smc: time: Unknown subfunction id %x\n",
+                subfunction_id);
+        return false;
+    }
+}
+
+static bool imx8qm_smc(struct cpu_user_regs *regs)
+{
+    uint32_t function_id = get_user_reg(regs, 0);
+    uint32_t subfunction_id = get_user_reg(regs, 1);
+    struct arm_smccc_res res;
+
+    if ( !cpus_have_const_cap(ARM_SMCCC_1_1) )
+    {
+        printk_once(XENLOG_WARNING
+                    "imx8qm: smc: no SMCCC 1.1 support. Disabling firmware calls\n");
+
+        return false;
+    }
+
+    /* Only hardware domain may use the SIP calls */
+    if ( !is_hardware_domain(current->domain) )
+    {
+        gprintk(XENLOG_WARNING, "imx8qm: smc: No access\n");
+        return false;
+    }
+
+    switch ( function_id )
+    {
+    case IMX_SIP_FID(IMX_SIP_F_CPUFREQ):
+        /* Hardware domain can't take any informed decision here */
+        return false;
+    case IMX_SIP_FID(IMX_SIP_F_TIME):
+        if ( imx8qm_is_sip_time_call_ok(subfunction_id) )
+            goto allow_call;
+        return false;
+    /* Xen doesn't have suspend support */
+    case IMX_SIP_FID(IMX_SIP_F_WAKEUP_SRC):
+        return false;
+    case IMX_SIP_FID(IMX_SIP_F_OTP_WRITE):
+        /* subfunction_id is the fuse number, no sensible check possible */
+        goto allow_call;
+    default:
+        gprintk(XENLOG_WARNING, "imx8qm: smc: Unknown function id %x\n",
+                function_id);
+        return false;
+    }
+
+ allow_call:
+    arm_smccc_1_1_smc(function_id,
+                      subfunction_id,
+                      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(imx8qm, "i.MX 8Q{M,XP}")
+    .compatible = imx8qm_dt_compat,
+    .smc = imx8qm_smc,
+PLATFORM_END
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */