ARM64: kernel: acpi: refactor ACPI tables init and checks

Current ACPI init code on ARM64 relies on acpi_table_parse() API to
check if the FADT is present and to carry out sanity checks on that.

The handler passed to the acpi_table_parse() function and used to
carry out the parsing on the requested table returns a value that is
ignored by the acpi_table_parse() function, so it is not possible
to propagate errors back to the acpi_table_parse() caller through
the handler.

This forces ARM64 ACPI init code to have disable_acpi() calls scattered
all over the place that makes code unwieldy and not easy to follow.

This patch refactors the ARM64 ACPI init code, by creating a
self-contained function (ie acpi_fadt_sanity_check()) that carries
out the required checks on FADT and returns an adequate return value
to the caller. This allows creating a common error path that disables
ACPI and makes code more readable and easy to parse and change were
further checks FADT to be added in the future.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 59 insertions, 36 deletions

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index a70f7141c0f6..172b7c9f6881 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -218,43 +218,60 @@ void __init acpi_init_cpus(void)
         pr_info("%d CPUs enabled, %d CPUs total\n", enabled_cpus, total_cpus);
 }
 
-static int __init acpi_parse_fadt(struct acpi_table_header *table)
+/*
+ * acpi_fadt_sanity_check() - Check FADT presence and carry out sanity
+ *                            checks on it
+ *
+ * Return 0 on success,  <0 on failure
+ */
+static int __init acpi_fadt_sanity_check(void)
 {
-        struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
+        struct acpi_table_header *table;
+        struct acpi_table_fadt *fadt;
+        acpi_status status;
+        acpi_size tbl_size;
+        int ret = 0;
+
+        /*
+         * FADT is required on arm64; retrieve it to check its presence
+         * and carry out revision and ACPI HW reduced compliancy tests
+         */
+        status = acpi_get_table_with_size(ACPI_SIG_FADT, 0, &table, &tbl_size);
+        if (ACPI_FAILURE(status)) {
+                const char *msg = acpi_format_exception(status);
+
+                pr_err("Failed to get FADT table, %s\n", msg);
+                return -ENODEV;
+        }
+
+        fadt = (struct acpi_table_fadt *)table;
 
         /*
          * Revision in table header is the FADT Major revision, and there
          * is a minor revision of FADT which was introduced by ACPI 5.1,
          * we only deal with ACPI 5.1 or newer revision to get GIC and SMP
-         * boot protocol configuration data, or we will disable ACPI.
+         * boot protocol configuration data.
          */
-        if (table->revision > 5 ||
-            (table->revision == 5 && fadt->minor_revision >= 1)) {
-                if (!acpi_gbl_reduced_hardware) {
-                        pr_err("Not hardware reduced ACPI mode, will not be supported\n");
-                        goto disable_acpi;
-                }
-
-                /*
-                 * ACPI 5.1 only has two explicit methods to boot up SMP,
-                 * PSCI and Parking protocol, but the Parking protocol is
-                 * only specified for ARMv7 now, so make PSCI as the only
-                 * way for the SMP boot protocol before some updates for
-                 * the Parking protocol spec.
-                 */
-                if (acpi_psci_present())
-                        return 0;
-
-                pr_warn("No PSCI support, will not bring up secondary CPUs\n");
-                return -EOPNOTSUPP;
+        if (table->revision < 5 ||
+           (table->revision == 5 && fadt->minor_revision < 1)) {
+                pr_err("Unsupported FADT revision %d.%d, should be 5.1+\n",
+                       table->revision, fadt->minor_revision);
+                ret = -EINVAL;
+                goto out;
         }
 
-        pr_warn("Unsupported FADT revision %d.%d, should be 5.1+, will disable ACPI\n",
-                table->revision, fadt->minor_revision);
+        if (!(fadt->flags & ACPI_FADT_HW_REDUCED)) {
+                pr_err("FADT not ACPI hardware reduced compliant\n");
+                ret = -EINVAL;
+        }
 
-disable_acpi:
-        disable_acpi();
-        return -EINVAL;
+out:
+        /*
+         * acpi_get_table_with_size() creates FADT table mapping that
+         * should be released after parsing and before resuming boot
+         */
+        early_acpi_os_unmap_memory(table, tbl_size);
+        return ret;
 }
 
 /*
@@ -262,9 +279,13 @@ disable_acpi:
  *      1. find RSDP and get its address, and then find XSDT
  *      2. extract all tables and checksums them all
  *      3. check ACPI FADT revision
+ *      4. check ACPI FADT HW reduced flag
  *
  * We can parse ACPI boot-time tables such as MADT after
  * this function is called.
+ *
+ * ACPI is enabled on return if ACPI tables initialized and sanity checks
+ * passed, disabled otherwise
  */
 void __init acpi_boot_table_init(void)
 {
@@ -278,18 +299,20 @@ void __init acpi_boot_table_init(void)
             (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
                 return;
 
+        /*
+         * ACPI is disabled at this point. Enable it in order to parse
+         * the ACPI tables and carry out sanity checks
+         */
         enable_acpi();
 
-        /* Initialize the ACPI boot-time table parser. */
-        if (acpi_table_init()) {
-                disable_acpi();
-                return;
-        }
-
-        if (acpi_table_parse(ACPI_SIG_FADT, acpi_parse_fadt)) {
-                /* disable ACPI if no FADT is found */
+        /*
+         * If ACPI tables are initialized and FADT sanity checks passed,
+         * leave ACPI enabled and carry on booting; otherwise disable ACPI
+         * on initialization error.
+         */
+        if (acpi_table_init() || acpi_fadt_sanity_check()) {
+                pr_err("Failed to init ACPI tables\n");
                 disable_acpi();
-                pr_err("Can't find FADT\n");
         }
 }