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

[Fu Wei <fu.wei@linaro.org>]

Hi Rafael,

On 14 July 2016 at 04:39, Rafael J. Wysocki <rafael@kernel.org> wrote:
> On Wed, Jul 13, 2016 at 10:30 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
>> On Wed, Jul 13, 2016 at 7:53 PM,  <fu.wei@linaro.org> wrote:
>>> From: Fu Wei <fu.wei@linaro.org>
>>>
>>> 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@linaro.org>
>>> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
>>> ---
>>>  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@linaro.org>
>>> + *         Fu Wei <fu.wei@linaro.org>
>>> + *         Hanjun Guo <hanjun.guo@linaro.org>
>>> + *
>>> + * 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;

Pretty good idea, will do , thanks :-)

>
> Thanks,
> Rafael



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat