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Message-ID: <20150325142623.GK24636@arm.com>
Date: Wed, 25 Mar 2015 14:26:23 +0000
From: Will Deacon <will.deacon@....com>
To: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
Catalin Marinas <Catalin.Marinas@....com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH 4/5] ARM64: kernel: acpi: refactor ACPI tables init and
checks
On Tue, Mar 24, 2015 at 05:58:54PM +0000, Lorenzo Pieralisi wrote:
> 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@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Hanjun Guo <hanjun.guo@...aro.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> ---
> arch/arm64/kernel/acpi.c | 104 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 70 insertions(+), 34 deletions(-)
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index a70f714..542f045 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;
> }
>
> /*
> @@ -262,12 +279,18 @@ 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)
> {
> + int err;
> +
> /*
> * Enable ACPI instead of device tree unless
> * - ACPI has been disabled explicitly (acpi=off), or
> @@ -278,19 +301,32 @@ 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;
> + err = acpi_table_init();
> + if (err) {
> + pr_err("Failed to init ACPI tables\n");
> + goto out;
> }
>
> - if (acpi_table_parse(ACPI_SIG_FADT, acpi_parse_fadt)) {
> - /* disable ACPI if no FADT is found */
> + /*
> + * Check FADT presence and carry out FADT sanity checks
> + */
> + err = acpi_fadt_sanity_check();
> +
> +out:
> + /*
> + * If ACPI tables are initialized and FADT sanity checks passed,
> + * leave ACPI enabled and carry on booting; otherwise disable ACPI
> + * on initialization error.
> + */
> + if (err)
> disable_acpi();
> - pr_err("Can't find FADT\n");
> - }
Could you rewrite most of this as:
enable_acpi();
if (acpi_table_init() || acpi_fadt_sanity_check()) {
pr_err("Failed to init ACPI tables\n");
disable_acpi();
}
I think it reads a bit better without the out: label.
Will
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