Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1505081 > unrolled thread

Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver Mark Rutland <mark.rutland@arm.com> - 2016-10-20 18:40 +0200
    Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver Fu Wei <fu.wei@linaro.org> - 2016-10-26 13:20 +0200
      Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver Marc Zyngier <marc.zyngier@arm.com> - 2016-10-26 14:20 +0200
        Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver Fu Wei <fu.wei@linaro.org> - 2016-10-26 15:50 +0200

#1505081 — Re: [PATCH v14 4/9] acpi/arm64: Add GTDT table parse driver

Hi,

As a heads-up, on v4.9-rc1 I see conflicts at least against
arch/arm64/Kconfig. Luckily git am -3 seems to be able to fix that up
automatically, but this will need to be rebased before the next posting
and/or merging.

On Thu, Sep 29, 2016 at 02:17:12AM +0800, fu.wei@linaro.org wrote:
> +static int __init map_gt_gsi(u32 interrupt, u32 flags)
> +{
> +	int trigger, polarity;
> +
> +	if (!interrupt)
> +		return 0;

Urgh.

Only the secure interrupt (which we do not need) is optional in this
manner, and (hilariously), zero appears to also be a valid GSIV, per
figure 5-24 in the ACPI 6.1 spec.

So, I think that:

(a) we should not bother parsing the secure interrupt
(b) we should drop the check above
(c) we should report the spec issue to the ASWG

> +/*
> + * acpi_gtdt_c3stop - got c3stop info from GTDT
> + *
> + * Returns 1 if the timer is powered in deep idle state, 0 otherwise.
> + */
> +bool __init acpi_gtdt_c3stop(void)
> +{
> +	struct acpi_table_gtdt *gtdt = acpi_gtdt_desc.gtdt;
> +
> +	return !(gtdt->non_secure_el1_flags & ACPI_GTDT_ALWAYS_ON);
> +}

It looks like this can differ per interrupt. Shouldn't we check the
appropriate one?

> +int __init acpi_gtdt_init(struct acpi_table_header *table)
> +{
> +	void *start;
> +	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);
> +		return 0;
> +	}
> +
> +	if (!gtdt->platform_timer_count) {
> +		pr_debug("No Platform Timer.\n");
> +		return 0;
> +	}
> +
> +	start = (void *)gtdt + gtdt->platform_timer_offset;
> +	if (start < (void *)table + sizeof(struct acpi_table_gtdt)) {
> +		pr_err(FW_BUG "Failed to retrieve timer info from firmware: invalid data.\n");
> +		return -EINVAL;
> +	}
> +	acpi_gtdt_desc.platform_timer_start = start;
> +
> +	return gtdt->platform_timer_count;
> +}

This is never used as anything other than a status code.

Just return zero; we haven't parsed the platform timers themselves at
this point anyway.

Thanks,
Mark.

[toc] | [next] | [standalone]

#1509074

Hi Mark,

On 21 October 2016 at 00:37, Mark Rutland <mark.rutland@arm.com> wrote:
> Hi,
>
> As a heads-up, on v4.9-rc1 I see conflicts at least against
> arch/arm64/Kconfig. Luckily git am -3 seems to be able to fix that up
> automatically, but this will need to be rebased before the next posting
> and/or merging.
>
> On Thu, Sep 29, 2016 at 02:17:12AM +0800, fu.wei@linaro.org wrote:
>> +static int __init map_gt_gsi(u32 interrupt, u32 flags)
>> +{
>> +     int trigger, polarity;
>> +
>> +     if (!interrupt)
>> +             return 0;
>
> Urgh.
>
> Only the secure interrupt (which we do not need) is optional in this
> manner, and (hilariously), zero appears to also be a valid GSIV, per
> figure 5-24 in the ACPI 6.1 spec.
>
> So, I think that:
>
> (a) we should not bother parsing the secure interrupt

If I understand correctly, from this point of view, kernel don't
handle the secure interrupt.
But the current arm_arch_timer driver still enable/disable/request
PHYS_SECURE_PPI
with PHYS_NONSECURE_PPI.
That means we still need to parse the secure interrupt.
Please correct me, if I misunderstand something? :-)

> (b) we should drop the check above

yes, if zero is a valid GSIV, this makes sense.

> (c) we should report the spec issue to the ASWG
>
>> +/*
>> + * acpi_gtdt_c3stop - got c3stop info from GTDT
>> + *
>> + * Returns 1 if the timer is powered in deep idle state, 0 otherwise.
>> + */
>> +bool __init acpi_gtdt_c3stop(void)
>> +{
>> +     struct acpi_table_gtdt *gtdt = acpi_gtdt_desc.gtdt;
>> +
>> +     return !(gtdt->non_secure_el1_flags & ACPI_GTDT_ALWAYS_ON);
>> +}
>
> It looks like this can differ per interrupt. Shouldn't we check the
> appropriate one?

yes, I think you are right.

>
>> +int __init acpi_gtdt_init(struct acpi_table_header *table)
>> +{
>> +     void *start;
>> +     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);
>> +             return 0;
>> +     }
>> +
>> +     if (!gtdt->platform_timer_count) {
>> +             pr_debug("No Platform Timer.\n");
>> +             return 0;
>> +     }
>> +
>> +     start = (void *)gtdt + gtdt->platform_timer_offset;
>> +     if (start < (void *)table + sizeof(struct acpi_table_gtdt)) {
>> +             pr_err(FW_BUG "Failed to retrieve timer info from firmware: invalid data.\n");
>> +             return -EINVAL;
>> +     }
>> +     acpi_gtdt_desc.platform_timer_start = start;
>> +
>> +     return gtdt->platform_timer_count;
>> +}
>
> This is never used as anything other than a status code.
>
> Just return zero; we haven't parsed the platform timers themselves at
> this point anyway.

Sorry, in my driver, I use this return value to inform driver

 negative number : error
0 : we don't have platform timer in GTDT table.
positive number: the number of platform timer we have in GTDT table.

please correct me, if I am doing it in wrong way. Thanks :-)


>
> Thanks,
> Mark.



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat

[toc] | [prev] | [next] | [standalone]

#1509124

On 26/10/16 12:10, Fu Wei wrote:
> Hi Mark,
> 
> On 21 October 2016 at 00:37, Mark Rutland <mark.rutland@arm.com> wrote:
>> Hi,
>>
>> As a heads-up, on v4.9-rc1 I see conflicts at least against
>> arch/arm64/Kconfig. Luckily git am -3 seems to be able to fix that up
>> automatically, but this will need to be rebased before the next posting
>> and/or merging.
>>
>> On Thu, Sep 29, 2016 at 02:17:12AM +0800, fu.wei@linaro.org wrote:
>>> +static int __init map_gt_gsi(u32 interrupt, u32 flags)
>>> +{
>>> +     int trigger, polarity;
>>> +
>>> +     if (!interrupt)
>>> +             return 0;
>>
>> Urgh.
>>
>> Only the secure interrupt (which we do not need) is optional in this
>> manner, and (hilariously), zero appears to also be a valid GSIV, per
>> figure 5-24 in the ACPI 6.1 spec.
>>
>> So, I think that:
>>
>> (a) we should not bother parsing the secure interrupt
> 
> If I understand correctly, from this point of view, kernel don't
> handle the secure interrupt.
> But the current arm_arch_timer driver still enable/disable/request
> PHYS_SECURE_PPI
> with PHYS_NONSECURE_PPI.
> That means we still need to parse the secure interrupt.
> Please correct me, if I misunderstand something? :-)

That's because we can use the per-cpu timer when 32bit Linux is running
on the secure side (and we cannot distinguish between secure and
non-secure at runtime). ACPI is 64bit only, and Linux on 64bit isn't
supported on the secure side, so only registering the non-secure timer
is perfectly acceptable.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

[toc] | [prev] | [next] | [standalone]

#1509448

Hi Marc,

On 26 October 2016 at 20:11, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On 26/10/16 12:10, Fu Wei wrote:
>> Hi Mark,
>>
>> On 21 October 2016 at 00:37, Mark Rutland <mark.rutland@arm.com> wrote:
>>> Hi,
>>>
>>> As a heads-up, on v4.9-rc1 I see conflicts at least against
>>> arch/arm64/Kconfig. Luckily git am -3 seems to be able to fix that up
>>> automatically, but this will need to be rebased before the next posting
>>> and/or merging.
>>>
>>> On Thu, Sep 29, 2016 at 02:17:12AM +0800, fu.wei@linaro.org wrote:
>>>> +static int __init map_gt_gsi(u32 interrupt, u32 flags)
>>>> +{
>>>> +     int trigger, polarity;
>>>> +
>>>> +     if (!interrupt)
>>>> +             return 0;
>>>
>>> Urgh.
>>>
>>> Only the secure interrupt (which we do not need) is optional in this
>>> manner, and (hilariously), zero appears to also be a valid GSIV, per
>>> figure 5-24 in the ACPI 6.1 spec.
>>>
>>> So, I think that:
>>>
>>> (a) we should not bother parsing the secure interrupt
>>
>> If I understand correctly, from this point of view, kernel don't
>> handle the secure interrupt.
>> But the current arm_arch_timer driver still enable/disable/request
>> PHYS_SECURE_PPI
>> with PHYS_NONSECURE_PPI.
>> That means we still need to parse the secure interrupt.
>> Please correct me, if I misunderstand something? :-)
>
> That's because we can use the per-cpu timer when 32bit Linux is running
> on the secure side (and we cannot distinguish between secure and
> non-secure at runtime). ACPI is 64bit only, and Linux on 64bit isn't
> supported on the secure side, so only registering the non-secure timer
> is perfectly acceptable.

Great thanks for your explanation :-)
So we just don't need to fill arch_timer_ppi[PHYS_SECURE_PPI] , just skip it.

>
> Thanks,
>
>         M.
> --
> Jazz is not dead. It just smells funny...



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web