ARM64 / ACPI: Introduce early_param "acpi=" to enable/disable ACPI

This implements the following policy to decide whether ACPI should
be used to boot the system:
- acpi=off: ACPI will not be used to boot the system, even if there is
  no alternative available (e.g., device tree is empty)
- acpi=force: only ACPI will be used to boot the system; if that fails,
  there will be no fallback to alternative methods (such as device tree)
- otherwise, ACPI will be used as a fallback if the device tree turns out
  to lack a platform description; the heuristic to decide this is whether
  /chosen is the only node present at depth 1

CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Rafael J. Wysocki <rjw@rjwysocki.net>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Grant Likely <grant.likely@linaro.org>
Tested-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Graeme Gregory <graeme.gregory@linaro.org>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bfcb1a6..d6c35a7 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -165,7 +165,7 @@ multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
 bytes respectively. Such letter suffixes can also be entirely omitted.
 
 
-       acpi=           [HW,ACPI,X86]
+       acpi=           [HW,ACPI,X86,ARM64]
                        Advanced Configuration and Power Interface
                        Format: { force | off | strict | noirq | rsdt }
                        force -- enable ACPI if default was off
@@ -175,6 +175,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                                strictly ACPI specification compliant.
                        rsdt -- prefer RSDT over (default) XSDT
                        copy_dsdt -- copy DSDT to memory
+                       For ARM64, ONLY "acpi=off" or "acpi=force" are available
 
                        See also Documentation/power/runtime_pm.txt, pci=noacpi
 

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 40e0924..c5a9b97 100644 (file)
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -39,6 +39,13 @@ static inline void disable_acpi(void)
        acpi_noirq = 1;
 }
 
+static inline void enable_acpi(void)
+{
+       acpi_disabled = 0;
+       acpi_pci_disabled = 0;
+       acpi_noirq = 0;
+}
+
 /*
  * It's used from ACPI core in kdump to boot UP system with SMP kernel,
  * with this check the ACPI core will not override the CPU index

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 7abac24..2269e30 100644 (file)
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -22,15 +22,49 @@
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/memblock.h>
+#include <linux/of_fdt.h>
 #include <linux/smp.h>
 
-int acpi_noirq;                        /* skip ACPI IRQ initialization */
-int acpi_disabled;
+int acpi_noirq = 1;            /* skip ACPI IRQ initialization */
+int acpi_disabled = 1;
 EXPORT_SYMBOL(acpi_disabled);
 
-int acpi_pci_disabled;         /* skip ACPI PCI scan and IRQ initialization */
+int acpi_pci_disabled = 1;     /* skip ACPI PCI scan and IRQ initialization */
 EXPORT_SYMBOL(acpi_pci_disabled);
 
+static bool param_acpi_off __initdata;
+static bool param_acpi_force __initdata;
+
+static int __init parse_acpi(char *arg)
+{
+       if (!arg)
+               return -EINVAL;
+
+       /* "acpi=off" disables both ACPI table parsing and interpreter */
+       if (strcmp(arg, "off") == 0)
+               param_acpi_off = true;
+       else if (strcmp(arg, "force") == 0) /* force ACPI to be enabled */
+               param_acpi_force = true;
+       else
+               return -EINVAL; /* Core will print when we return error */
+
+       return 0;
+}
+early_param("acpi", parse_acpi);
+
+static int __init dt_scan_depth1_nodes(unsigned long node,
+                                      const char *uname, int depth,
+                                      void *data)
+{
+       /*
+        * Return 1 as soon as we encounter a node at depth 1 that is
+        * not the /chosen node.
+        */
+       if (depth == 1 && (strcmp(uname, "chosen") != 0))
+               return 1;
+       return 0;
+}
+
 /*
  * __acpi_map_table() will be called before page_init(), so early_ioremap()
  * or early_memremap() should be called here to for ACPI table mapping.
@@ -83,10 +117,18 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table)
  */
 void __init acpi_boot_table_init(void)
 {
-       /* If acpi_disabled, bail out */
-       if (acpi_disabled)
+       /*
+        * Enable ACPI instead of device tree unless
+        * - ACPI has been disabled explicitly (acpi=off), or
+        * - the device tree is not empty (it has more than just a /chosen node)
+        *   and ACPI has not been force enabled (acpi=force)
+        */
+       if (param_acpi_off ||
+           (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
                return;
 
+       enable_acpi();
+
        /* Initialize the ACPI boot-time table parser. */
        if (acpi_table_init()) {
                disable_acpi();