Re: [PATCH v7 4/9] acpi/arm64: Add GTDT table parse driver

From: Rafael J. Wysocki
Date: Wed Jul 13 2016 - 16:39:51 EST

On Wed, Jul 13, 2016 at 10:30 PM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> On Wed, Jul 13, 2016 at 7:53 PM, <fu.wei@xxxxxxxxxx> wrote:
>> From: Fu Wei <fu.wei@xxxxxxxxxx>
>>
>> This patch adds support for parsing arch timer 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@xxxxxxxxxx>
>> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> ---
>> drivers/acpi/Kconfig | 5 ++
>> drivers/acpi/Makefile | 1 +
>> drivers/acpi/arm64/Kconfig | 15 ++++
>> drivers/acpi/arm64/Makefile | 1 +
>> drivers/acpi/arm64/acpi_gtdt.c | 170 +++++++++++++++++++++++++++++++++++++++++
>> include/linux/acpi.h | 6 ++
>> 6 files changed, 198 insertions(+)
>>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index b7e2e77..1cdc7d2 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -521,4 +521,9 @@ config XPOWER_PMIC_OPREGION
>>
>> endif
>>
>> +if ARM64
>> +source "drivers/acpi/arm64/Kconfig"
>> +
>> +endif
>> +
>> endif # ACPI
>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>> index 251ce85..1a94ff7 100644
>> --- a/drivers/acpi/Makefile
>> +++ b/drivers/acpi/Makefile
>> @@ -99,5 +99,6 @@ obj-$(CONFIG_ACPI_EXTLOG) += acpi_extlog.o
>> obj-$(CONFIG_PMIC_OPREGION) += pmic/intel_pmic.o
>> obj-$(CONFIG_CRC_PMIC_OPREGION) += pmic/intel_pmic_crc.o
>> obj-$(CONFIG_XPOWER_PMIC_OPREGION) += pmic/intel_pmic_xpower.o
>> +obj-$(CONFIG_ARM64) += arm64/
>>
>> video-objs += acpi_video.o video_detect.o
>> diff --git a/drivers/acpi/arm64/Kconfig b/drivers/acpi/arm64/Kconfig
>> new file mode 100644
>> index 0000000..ff5c253
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/Kconfig
>> @@ -0,0 +1,15 @@
>> +#
>> +# ACPI Configuration for ARM64
>> +#
>> +
>> +menu "The ARM64-specific ACPI Support"
>> +
>> +config ACPI_GTDT
>> + bool "ACPI GTDT table Support"
>
> This should depend on ARM64.
>
> Also I wonder if it needs to be user-selectable? Wouldn't it be
> better to enable it by default when building for ARM64 with ACPI?
>
>> + help
>> + GTDT (Generic Timer Description Table) provides information
>> + for per-processor timers and Platform (memory-mapped) timers
>> + for ARM platforms. Select this option to provide information
>> + needed for the timers init.
>> +
>> +endmenu
>> diff --git a/drivers/acpi/arm64/Makefile b/drivers/acpi/arm64/Makefile
>> new file mode 100644
>> index 0000000..466de6b
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/Makefile
>> @@ -0,0 +1 @@
>> +obj-$(CONFIG_ACPI_GTDT) += acpi_gtdt.o
>> diff --git a/drivers/acpi/arm64/acpi_gtdt.c b/drivers/acpi/arm64/acpi_gtdt.c
>> new file mode 100644
>> index 0000000..9ee977d
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/acpi_gtdt.c
>> @@ -0,0 +1,170 @@
>> +/*
>> + * ARM Specific GTDT table Support
>> + *
>> + * Copyright (C) 2016, Linaro Ltd.
>> + * Author: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
>> + * Fu Wei <fu.wei@xxxxxxxxxx>
>> + * Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +
>> +#include <linux/acpi.h>
>> +#include <linux/init.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +
>> +#include <clocksource/arm_arch_timer.h>
>> +
>> +#undef pr_fmt
>> +#define pr_fmt(fmt) "GTDT: " fmt
>
> I would add "ACPI" to the prefix too if I were you, but that's me.
>
>> +
>> +typedef struct {
>> + struct acpi_table_gtdt *gtdt;
>> + void *platform_timer_start;
>> + void *gtdt_end;
>> +} acpi_gtdt_desc_t;
>> +
>> +static acpi_gtdt_desc_t acpi_gtdt_desc __initdata;
>> +
>> +static inline void *next_platform_timer(void *platform_timer)
>> +{
>> + struct acpi_gtdt_header *gh = platform_timer;
>> +
>> + platform_timer += gh->length;
>> + if (platform_timer < acpi_gtdt_desc.gtdt_end)
>> + return platform_timer;
>> +
>> + return NULL;
>> +}
>> +
>> +#define for_each_platform_timer(_g) \
>> + for (_g = acpi_gtdt_desc.platform_timer_start; _g; \
>> + _g = next_platform_timer(_g))
>> +
>> +static inline bool is_timer_block(void *platform_timer)
>> +{
>> + struct acpi_gtdt_header *gh = platform_timer;
>> +
>> + if (gh->type == ACPI_GTDT_TYPE_TIMER_BLOCK)
>> + return true;
>> +
>> + return false;
>
> This is just too much code. It would suffice to do
>
> return gh->type == ACPI_GTDT_TYPE_TIMER_BLOCK;
>
>> +}
>> +
>> +static inline bool is_watchdog(void *platform_timer)
>> +{
>> + struct acpi_gtdt_header *gh = platform_timer;
>> +
>> + if (gh->type == ACPI_GTDT_TYPE_WATCHDOG)
>> + return true;
>> +
>> + return false;
>
> Just like above.
>
>> +}
>> +
>> +/*
>> + * Get some basic info from GTDT table, and init the global variables above
>> + * for all timers initialization of Generic Timer.
>> + * This function does some validation on GTDT table.
>> + */
>> +static int __init acpi_gtdt_desc_init(struct acpi_table_header *table)
>> +{
>> + struct acpi_table_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_info("Revision:%d doesn't support Platform Timers.\n",
>> + table->revision);
>
> Is it really useful to print this message (and the one below) at the
> "info" level? What about changing them to pr_debug()?
>
>> + return 0;
>> + }
>> +
>> + if (!gtdt->platform_timer_count) {
>> + pr_info("No Platform Timer.\n");
>> + return 0;
>> + }
>> +
>> + acpi_gtdt_desc.platform_timer_start = (void *)gtdt +
>> + gtdt->platform_timer_offset;

BTW, breaking lines this way doesn't make the code particularly more readable.

>> + if (acpi_gtdt_desc.platform_timer_start <
>> + (void *)table + sizeof(struct acpi_table_gtdt)) {

Same here.

It might be avoided by using a local (void *) variable "start", ie.

start = (void *)gtdt + gtdt->platform_timer_offset;
if (start < (void *)table + sizeof(struct acpi_table_gtdt))) {
print message;
return -EINVAL;
}
acpi_gtdt_desc.platform_timer_start = start;

Thanks,
Rafael