Re: [PATCH v16 13/15] acpi/arm64: Add memory-mapped timer support in GTDT driver

[Fu Wei]

Hi Lorenzo,

On 18 November 2016 at 22:22, Lorenzo Pieralisi
<lorenzo.pieralisi@xxxxxxx> wrote:
> On Wed, Nov 16, 2016 at 09:49:06PM +0800, fu.wei@xxxxxxxxxx wrote:
>> From: Fu Wei <fu.wei@xxxxxxxxxx>
>>
>> On platforms booting with ACPI, architected memory-mapped timers'
>> configuration data is provided by firmware through the ACPI GTDT
>> static table.
>>
>> The clocksource architected timer kernel driver requires a firmware
>> interface to collect timer configuration and configure its driver.
>> this infrastructure is present for device tree systems, but it is
>> missing on systems booting with ACPI.
>>
>> Implement the kernel infrastructure required to parse the static
>> ACPI GTDT table so that the architected timer clocksource driver can
>> make use of it on systems booting with ACPI, therefore enabling
>> the corresponding timers configuration.
>>
>> Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
>> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> ---
>>  drivers/acpi/arm64/gtdt.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/acpi.h      |  1 +
>>  2 files changed, 96 insertions(+)
>>
>> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
>> index 2de79aa..08d9506 100644
>> --- a/drivers/acpi/arm64/gtdt.c
>> +++ b/drivers/acpi/arm64/gtdt.c
>> @@ -51,6 +51,14 @@ static inline bool is_timer_block(void *platform_timer)
>>       return gh->type == ACPI_GTDT_TYPE_TIMER_BLOCK;
>>  }
>>
>> +static inline struct acpi_gtdt_timer_block *get_timer_block(unsigned int index)
>> +{
>> +     if (index >= acpi_gtdt_desc.timer_block_count || !timer_block)
>> +             return NULL;
>> +
>> +     return timer_block[index];
>> +}
>> +
>>  static inline bool is_watchdog(void *platform_timer)
>>  {
>>       struct acpi_gtdt_header *gh = platform_timer;
>> @@ -214,3 +222,90 @@ int __init acpi_gtdt_init(struct acpi_table_header *table)
>>       acpi_gtdt_release();
>>       return -EINVAL;
>>  }
>> +
>> +/*
>> + * Get ONE GT block info for memory-mapped timer from GTDT table.
>> + * @data: the GT block data (parsing result)
>> + * @index: the index number of GT block
>> + * Note: we already verify @data in caller, it can't be NULL here.
>> + * Returns 0 if success, -EINVAL/-ENODEV if error.
>> + */
>
> Documentation/kernel-doc-nano-HOWTO.txt

Great thanks , will fix all the comments :-)

>
>> +int __init gtdt_arch_timer_mem_init(struct arch_timer_mem *data,
>> +                                 unsigned int index)
>
> Nit: acpi_arch_timer_mem_init() to make it consistent with other ACPI
> calls ?

yes, it makes sense, will do this way for the function  which is exported

>
>> +{
>> +     struct acpi_gtdt_timer_block *block;
>> +     struct acpi_gtdt_timer_entry *frame;
>> +     int i;
>> +
>> +     block = get_timer_block(index);
>> +     if (!block)
>> +             return -ENODEV;
>> +
>> +     if (!block->timer_count) {
>> +             pr_err(FW_BUG "GT block present, but frame count is zero.");
>> +             return -ENODEV;
>> +     }
>> +
>> +     if (block->timer_count > ARCH_TIMER_MEM_MAX_FRAMES) {
>> +             pr_err(FW_BUG "GT block lists %d frames, ACPI spec only allows 8\n",
>> +                    block->timer_count);
>> +             return -EINVAL;
>> +     }
>
> Nit: these two checks can be carried out at GTDT init where the GTDT
> is parsed first. Actually you could have two functions one to init

this check is  the verify the data in GT block, but the GTDT init
won't get into the block,
so I think that is better to keep this in GT block init function
"acpi_arch_timer_mem_init()"

> timers (say acpi_gtdt_timers_init()) and one watchdogs, that would
> eliminate the duplicated timer_block/watchdog arrays (both sized
> Platform Timer Count) and acpi_gtdt_timers_init() can return
> the number of entries found so that you can loop with a determined
> upper bound in the arm arch timer driver.

Yes, I did this way in previous patchset, but we still need to do scan
loop in both  functions for
two types of platform timer.
So I decide to keep the scan loop in the acpi_gtdt_init to get the
number and the entries pointer
of each type of platform timers in one go.  then we don't need to scan
GTDT in two functions.

>
> Just thinking aloud, these are just improvements I can carry them
> out later, the more important question here is the interface between the
> parsing code and the arch timer probing code which depends on other
> patches and that needs to be agreed, this patch is not really a problem.

yes, every time I modify the interface I have to change the driver :-(

>
>> +     data->cntctlbase = (phys_addr_t)block->block_address;
>> +     /*
>> +      * We can NOT get the size info from GTDT table,
>> +      * but according to "Table * CNTCTLBase memory map" of
>> +      * <ARM Architecture Reference Manual> for ARMv8,
>> +      * it should be 4KB(Offset 0x000 â 0xFFC).
>
> That's the reason why it is not explicit in the GTDT table :)
>
>> +     data->size = SZ_4K;
>> +     data->num_frames = block->timer_count;
>> +
>> +     frame = (void *)block + block->timer_offset;
>> +     if (frame + block->timer_count != (void *)block + block->header.length)
>> +             return -EINVAL;
>> +
>> +     /*
>> +      * Get the GT timer Frame data for every GT Block Timer
>> +      */
>> +     for (i = 0; i < block->timer_count; i++, frame++) {
>> +             if (!frame->base_address || !frame->timer_interrupt)
>> +                     return -EINVAL;
>> +
>> +             data->frame[i].phys_irq = map_gt_gsi(frame->timer_interrupt,
>> +                                                  frame->timer_flags);
>> +             if (data->frame[i].phys_irq <= 0) {
>> +                     pr_warn("failed to map physical timer irq in frame %d.\n",
>> +                             i);
>> +                     return -EINVAL;
>> +             }
>> +
>> +             if (frame->virtual_timer_interrupt) {
>> +                     data->frame[i].virt_irq =
>> +                             map_gt_gsi(frame->virtual_timer_interrupt,
>> +                                        frame->virtual_timer_flags);
>> +                     if (data->frame[i].virt_irq <= 0) {
>> +                             pr_warn("failed to map virtual timer irq in frame %d.\n",
>> +                                     i);
>> +                             return -EINVAL;
>
> You should unregister phys_irq here for correctness, right ?

yup, thanks for pointing this  bug out. :-)

>
>> +                     }
>> +             }
>> +
>> +             data->frame[i].frame_nr = frame->frame_number;
>> +             data->frame[i].cntbase = frame->base_address;
>> +             /*
>> +              * We can NOT get the size info from GTDT table,
>> +              * but according to "Table * CNTBaseN memory map" of
>> +              * <ARM Architecture Reference Manual> for ARMv8,
>> +              * it should be 4KB(Offset 0x000 â 0xFFC).
>
> See above.

yes, you are right, I will fix both comments

>
>> +              */
>> +             data->frame[i].size = SZ_4K;
>> +     }
>> +
>> +     if (acpi_gtdt_desc.timer_block_count)
>> +             pr_info("parsed No.%d of %d memory-mapped timer block(s).\n",
>> +                     index, acpi_gtdt_desc.timer_block_count);
>
> I am not sure how helpful this message can be honestly.

yup, I will simplify it  :-)

>
>> +
>> +     return 0;
>> +}
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index a1611d1..44b8c1b 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -582,6 +582,7 @@ int acpi_gtdt_init(struct acpi_table_header *table);
>>  int acpi_gtdt_map_ppi(int type);
>>  bool acpi_gtdt_c3stop(int type);
>>  void acpi_gtdt_release(void);
>> +int gtdt_arch_timer_mem_init(struct arch_timer_mem *data, unsigned int index);
>
> See above.
>
> Overall it looks fine as long as the interface with clocksource is
> settled, which is what really needs to be agreed upon in this series.

Thanks for your help :-)

>
> Lorenzo
>
>>  #endif
>>
>>  #else        /* !CONFIG_ACPI */
>> --
>> 2.7.4
>>



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat