Re: [PATCH v20 13/17] acpi/arm64: Add GTDT table parse driver

Hanjun Guo
2017-01-19T09:11:29Z

On 2017/1/18 21:25, fu.wei@linaro.org wrote:
> From: Fu Wei <fu.wei@linaro.org>
>
> This patch adds support for parsing arch timer info in GTDT,
> provides some kernel APIs to parse all the PPIs and
> always-on info in GTDT and export them.
>
> By this driver, we can simplify arm_arch_timer drivers, and
> separate the ACPI GTDT knowledge from it.
>
> Signed-off-by: Fu Wei <fu.wei@linaro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Tested-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
> ---
> arch/arm64/Kconfig | 1 +
> drivers/acpi/arm64/Kconfig | 3 +
> drivers/acpi/arm64/Makefile | 1 +
> drivers/acpi/arm64/gtdt.c | 157 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/acpi.h | 6 ++
> 5 files changed, 168 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1117421..ab1ee10 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -2,6 +2,7 @@ config ARM64
> def_bool y
> select ACPI_CCA_REQUIRED if ACPI
> select ACPI_GENERIC_GSI if ACPI
> + select ACPI_GTDT if ACPI
> select ACPI_REDUCED_HARDWARE_ONLY if ACPI
> select ACPI_MCFG if ACPI
> select ACPI_SPCR_TABLE if ACPI
> diff --git a/drivers/acpi/arm64/Kconfig b/drivers/acpi/arm64/Kconfig
> index 4616da4..5a6f80f 100644
> --- a/drivers/acpi/arm64/Kconfig
> +++ b/drivers/acpi/arm64/Kconfig
> @@ -4,3 +4,6 @@
>
> config ACPI_IORT
> bool
> +
> +config ACPI_GTDT
> + bool
> diff --git a/drivers/acpi/arm64/Makefile b/drivers/acpi/arm64/Makefile
> index 72331f2..1017def 100644
> --- a/drivers/acpi/arm64/Makefile
> +++ b/drivers/acpi/arm64/Makefile
> @@ -1 +1,2 @@
> obj-$(CONFIG_ACPI_IORT) += iort.o
> +obj-$(CONFIG_ACPI_GTDT) += gtdt.o
> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
> new file mode 100644
> index 0000000..d93a790
> --- /dev/null
> +++ b/drivers/acpi/arm64/gtdt.c
> @@ -0,0 +1,157 @@
[...]
> +
> +/**
> + * acpi_gtdt_init() - Get the info of GTDT table to prepare for further init.
> + * @table: The pointer to GTDT table.
> + * @platform_timer_count: The pointer of int variate for returning the
> + * number of platform timers. It can be NULL, if
> + * driver don't need this info.
> + *
> + * Return: 0 if success, -EINVAL if error.
> + */
> +int __init acpi_gtdt_init(struct acpi_table_header *table,
> + int *platform_timer_count)
> +{
> + int ret = 0;
> + int timer_count = 0;
> + void *platform_timer = NULL;
> + struct acpi_table_gtdt *gtdt;
> +
> + gtdt = container_of(table, struct acpi_table_gtdt, header);
> + acpi_gtdt_desc.gtdt = gtdt;
> + acpi_gtdt_desc.gtdt_end = (void *)table + table->length;
> +
> + if (table->revision < 2)
> + pr_debug("Revision:%d doesn't support Platform Timers.\n",
> + table->revision);

GTDT table revision is updated to 2 in ACPI 5.1, we will
not support ACPI version under 5.1 and disable ACPI in FADT
parse before this code is called, so if we get revision
<2 here, I think we need to print warning (we need to keep
the firmware stick to the spec on ARM64).

> + else if (!gtdt->platform_timer_count)
> + pr_debug("No Platform Timer.\n");
> + else
> + timer_count = gtdt->platform_timer_count;
> +
> + if (timer_count) {
> + platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
> + if (platform_timer < (void *)table +
> + sizeof(struct acpi_table_gtdt)) {
> + pr_err(FW_BUG "invalid timer data.\n");

It's ok but I didn't see other ACPI tables parsing did this check,
maybe we can just remove it :)

> + timer_count = 0;
> + platform_timer = NULL;
> + ret = -EINVAL;
> + }
> + }
> +
> + acpi_gtdt_desc.platform_timer = platform_timer;
> + if (platform_timer_count)
> + *platform_timer_count = timer_count;

Then the code will much simple:

if (gtdt->platform_timer_count) {
acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
if (platform_timer_count)
*platform_timer_count = gtdt->platform_timer_count;
}

return 0;

and remove ret, timer_count and platform_timer.

Thanks
Hanjun