Re: [PATCH v22 07/11] acpi/arm64: Add GTDT table parse driver

From: Fu Wei
Date: Wed Mar 29 2017 - 05:48:33 EST

Hi Lorenzo,

Great thanks for your review and help, I will take most of your suggestions,
But one or two comments have been discussed in previous patchset,
please allow me to explain these. :-)

On 28 March 2017 at 19:35, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote:
> On Wed, Mar 22, 2017 at 12:31:18AM +0800, fu.wei@xxxxxxxxxx wrote:
>> From: Fu Wei <fu.wei@xxxxxxxxxx>
>>
>> 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@xxxxxxxxxx>
>> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
>
> Some nits below.

Great thanks!

>
>> Tested-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
>> Reviewed-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> Tested-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> ---
>> 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 3741859..7e2baec 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..8a03b4b
>> --- /dev/null
>> +++ b/drivers/acpi/arm64/gtdt.c
>> @@ -0,0 +1,157 @@
>> +/*
>> + * 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 <clocksource/arm_arch_timer.h>
>> +
>> +#undef pr_fmt
>> +#define pr_fmt(fmt) "ACPI GTDT: " fmt
>> +
>> +/**
>> + * struct acpi_gtdt_descriptor - Store the key info of GTDT for all functions
>> + * @gtdt: The pointer to the struct acpi_table_gtdt of GTDT table.
>> + * @gtdt_end: The pointer to the end of GTDT table.
>> + * @platform_timer: The pointer to the start of Platform Timer Structure
>> + *
>> + * The struct store the key info of GTDT table, it should be initialized by
>> + * acpi_gtdt_init.
>> + */
>> +struct acpi_gtdt_descriptor {
>> + struct acpi_table_gtdt *gtdt;
>> + void *gtdt_end;
>> + void *platform_timer;
>> +};
>> +
>> +static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
>> +
>> +static int __init map_gt_gsi(u32 interrupt, u32 flags)
>> +{
>> + int trigger, polarity;
>> +
>> + trigger = (flags & ACPI_GTDT_INTERRUPT_MODE) ? ACPI_EDGE_SENSITIVE
>> + : ACPI_LEVEL_SENSITIVE;
>> +
>> + polarity = (flags & ACPI_GTDT_INTERRUPT_POLARITY) ? ACPI_ACTIVE_LOW
>> + : ACPI_ACTIVE_HIGH;
>> +
>> + return acpi_register_gsi(NULL, interrupt, trigger, polarity);
>> +}
>> +
>> +/**
>> + * acpi_gtdt_map_ppi() - Map the PPIs of per-cpu arch_timer.
>> + * @type: the type of PPI.
>> + *
>> + * Note: Linux on arm64 isn't supported on the secure side.
>
> Note: Secure state is not managed by the kernel on ARM64 systems.
>
> Is that what you wanted to say ?

yes, you are right, thanks! :-)
Will do so.

>
>> + * So we only handle the non-secure timer PPIs,
>> + * ARCH_TIMER_PHYS_SECURE_PPI is treated as invalid type.
>> + *
>> + * Return: the mapped PPI value, 0 if error.
>> + */
>> +int __init acpi_gtdt_map_ppi(int type)
>> +{
>> + struct acpi_table_gtdt *gtdt = acpi_gtdt_desc.gtdt;
>> +
>> + switch (type) {
>> + case ARCH_TIMER_PHYS_NONSECURE_PPI:
>> + return map_gt_gsi(gtdt->non_secure_el1_interrupt,
>> + gtdt->non_secure_el1_flags);
>> + case ARCH_TIMER_VIRT_PPI:
>> + return map_gt_gsi(gtdt->virtual_timer_interrupt,
>> + gtdt->virtual_timer_flags);
>> +
>> + case ARCH_TIMER_HYP_PPI:
>> + return map_gt_gsi(gtdt->non_secure_el2_interrupt,
>> + gtdt->non_secure_el2_flags);
>> + default:
>> + pr_err("Failed to map timer interrupt: invalid type.\n");
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * acpi_gtdt_c3stop() - Got c3stop info from GTDT according to the type of PPI.
>> + * @type: the type of PPI.
>> + *
>> + * Return: 1 if the timer can be in deep idle state, 0 otherwise.
>
> Return: true if the timer HW state is lost when a CPU enters an idle
> state, false otherwise

Thanks , will do

>
>> + */
>> +bool __init acpi_gtdt_c3stop(int type)
>> +{
>> + struct acpi_table_gtdt *gtdt = acpi_gtdt_desc.gtdt;
>> +
>> + switch (type) {
>> + case ARCH_TIMER_PHYS_NONSECURE_PPI:
>> + return !(gtdt->non_secure_el1_flags & ACPI_GTDT_ALWAYS_ON);
>> +
>> + case ARCH_TIMER_VIRT_PPI:
>> + return !(gtdt->virtual_timer_flags & ACPI_GTDT_ALWAYS_ON);
>> +
>> + case ARCH_TIMER_HYP_PPI:
>> + return !(gtdt->non_secure_el2_flags & ACPI_GTDT_ALWAYS_ON);
>> +
>> + default:
>> + pr_err("Failed to get c3stop info: invalid type.\n");
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * 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
>
> I do not understand what this means.
>
>> + * number of platform timers. It can be NULL, if
>> + * driver don't need this info.
>
> driver doesn't

Sorry, this is not clear, I will fix it by :

* @platform_timer_count: It points to a integer variable which is used
* for storing the number of platform timers.
* This pointer could be NULL, if the caller
* doesn'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_warn("Revision:%d doesn't support Platform Timers.\n",
>> + table->revision);
>
> Ok, two points here. First, I am not sure why you should warn if the
> table revision is < 2, is that a FW bug ? I do not think it is, you
> can just return 0.

I used pr_debug here before v20, then I got Hanjun's suggestion:
-------
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).
-------
https://lkml.org/lkml/2017/1/19/82

So I started to use pr_warn.

>
>> + else if (!gtdt->platform_timer_count)
>> + pr_debug("No Platform Timer.\n");
>
> Ditto. Why keep executing ? There is nothing to do, just bail out
> with a return 0.
>
>> + 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");
>> + timer_count = 0;
>> + platform_timer = NULL;
>> + ret = -EINVAL;
>
> Same here, I suspect you want to consolidate the return path (I missed
> previous rounds of reviews so you should not worry too much, I can clean
> this up later) but to me a:
>
> return -EINVAL;
>
> would just do.

yes, you are right, I try to consolidate the return path. :-)
It may can return earlier, let me try.

>
> Lorenzo
>
>> + }
>> + }
>> +
>> + acpi_gtdt_desc.platform_timer = platform_timer;
>> + if (platform_timer_count)
>> + *platform_timer_count = timer_count;
>> +
>> + return ret;
>> +}
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index 9b05886..4b5c146 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -595,6 +595,12 @@ enum acpi_reconfig_event {
>> int acpi_reconfig_notifier_register(struct notifier_block *nb);
>> int acpi_reconfig_notifier_unregister(struct notifier_block *nb);
>>
>> +#ifdef CONFIG_ACPI_GTDT
>> +int acpi_gtdt_init(struct acpi_table_header *table, int *platform_timer_count);
>> +int acpi_gtdt_map_ppi(int type);
>> +bool acpi_gtdt_c3stop(int type);
>> +#endif
>> +
>> #else /* !CONFIG_ACPI */
>>
>> #define acpi_disabled 1
>> --
>> 2.9.3
>>



--
Best regards,

Fu Wei
Software Engineer
Red Hat