Re: [PATCH v22 11/11] acpi/arm64: Add SBSA Generic Watchdog support in GTDT driver

[Fu Wei]

Hi Lorenzo,

On 28 March 2017 at 23:41, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote:
> On Wed, Mar 22, 2017 at 12:31:22AM +0800, fu.wei@xxxxxxxxxx wrote:
>> From: Fu Wei <fu.wei@xxxxxxxxxx>
>>
>> This driver adds support for parsing SBSA Generic Watchdog timer
>> in GTDT, parse all info in SBSA Generic Watchdog Structure in GTDT,
>> and creating a platform device with that information.
>>
>> This allows the operating system to obtain device data from the
>> resource of platform device. The platform device named "sbsa-gwdt"
>> can be used by the ARM SBSA Generic Watchdog driver.
>>
>> Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
>> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
>> Tested-by: Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
>> ---
>>  drivers/acpi/arm64/gtdt.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 94 insertions(+)
>>
>> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
>> index f471873..5d167f0 100644
>> --- a/drivers/acpi/arm64/gtdt.c
>> +++ b/drivers/acpi/arm64/gtdt.c
>> @@ -14,6 +14,7 @@
>>  #include <linux/acpi.h>
>>  #include <linux/init.h>
>>  #include <linux/kernel.h>
>> +#include <linux/platform_device.h>
>>
>>  #include <clocksource/arm_arch_timer.h>
>>
>> @@ -59,6 +60,17 @@ static inline bool is_timer_block(void *platform_timer)
>>       return gh->type == ACPI_GTDT_TYPE_TIMER_BLOCK;
>>  }
>>
>> +static inline bool is_non_secure_watchdog(void *platform_timer)
>> +{
>> +     struct acpi_gtdt_header *gh = platform_timer;
>> +     struct acpi_gtdt_watchdog *wd = platform_timer;
>> +
>> +     if (gh->type != ACPI_GTDT_TYPE_WATCHDOG)
>> +             return false;
>> +
>> +     return !(wd->timer_flags & ACPI_GTDT_WATCHDOG_SECURE);
>> +}
>> +
>>  static int __init map_gt_gsi(u32 interrupt, u32 flags)
>>  {
>>       int trigger, polarity;
>> @@ -285,3 +297,85 @@ int __init acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem,
>>
>>       return 0;
>>  }
>> +
>> +/*
>> + * Initialize a SBSA generic Watchdog platform device info from GTDT
>> + */
>> +static int __init gtdt_import_sbsa_gwdt(struct acpi_gtdt_watchdog *wd,
>> +                                     int index)
>> +{
>> +     struct platform_device *pdev;
>> +     int irq = map_gt_gsi(wd->timer_interrupt, wd->timer_flags);
>> +
>> +     /*
>> +      * According to SBSA specification the size of refresh and control
>> +      * frames of SBSA Generic Watchdog is SZ_4K(Offset 0x000 â 0xFFF).
>> +      */
>> +     struct resource res[] = {
>> +             DEFINE_RES_MEM(wd->control_frame_address, SZ_4K),
>> +             DEFINE_RES_MEM(wd->refresh_frame_address, SZ_4K),
>> +             DEFINE_RES_IRQ(irq),
>> +     };
>> +     int nr_res = ARRAY_SIZE(res);
>> +
>> +     pr_debug("found a Watchdog (0x%llx/0x%llx gsi:%u flags:0x%x).\n",
>> +              wd->refresh_frame_address, wd->control_frame_address,
>> +              wd->timer_interrupt, wd->timer_flags);
>> +
>> +     if (!(wd->refresh_frame_address && wd->control_frame_address)) {
>> +             pr_err(FW_BUG "failed to get the Watchdog base address.\n");


+             acpi_unregister_gsi(wd->timer_interrupt);


>> +             return -EINVAL;
>
> You should unmap the gsi here.

yes, you are right, fixed it.

>
>> +     }
>> +
>> +     if (irq <= 0) {
>> +             pr_warn("failed to map the Watchdog interrupt.\n");
>> +             nr_res--;
>> +     }
>> +
>> +     /*
>> +      * Add a platform device named "sbsa-gwdt" to match the platform driver.
>> +      * "sbsa-gwdt": SBSA(Server Base System Architecture) Generic Watchdog
>> +      * The platform driver (like drivers/watchdog/sbsa_gwdt.c)can get device

+      * The platform driver can get device info below by matching this name.

>
> Nit: I would not hardcode drivers paths in comments.


OK, deleted it

>
>> +      * info below by matching this name.
>> +      */
>> +     pdev = platform_device_register_simple("sbsa-gwdt", index, res, nr_res);
>> +     if (IS_ERR(pdev)) {
>> +             acpi_unregister_gsi(wd->timer_interrupt);
>> +             return PTR_ERR(pdev);
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +static int __init gtdt_sbsa_gwdt_init(void)
>> +{
>> +     int ret, i = 0;
>> +     void *platform_timer;
>> +     struct acpi_table_header *table;
>> +
>> +     if (acpi_disabled)
>> +             return 0;
>> +
>> +     if (ACPI_FAILURE(acpi_get_table(ACPI_SIG_GTDT, 0, &table)))
>> +             return -EINVAL;
>> +
>> +     ret = acpi_gtdt_init(table, NULL);
>> +     if (ret)
>> +             return ret;
>
> Ok, I missed previous versions reviews so I miss the background
> here and I apologise.
>
> I do not understand why you call acpi_gtdt_init() again (or better,
> why acpi_gtdt_init() does not return straight away) here if the
> stashed pointer in acpi_gtdt_desc is already set. I am not a big fan
> of the for_each_platform_timer macro either, here you can just read
> the ACPI_SIG_GTDT and parse its entries, I see no point in calling
> acpi_gtdt_init() again, there is nothing to stash for later probing,
> is there ?
>
> Or it is just to reuse common parsing code ? Regardless, if the
> acpi_gtdt_desc struct is already initialized acpi_gtdt_init() should
> just return or I am missing the point.
>
> I would like clarifications on the acpi_gtdt_init() call above please
> (plus GSI unmap fix), apart from that:
>
> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>

Actually, after the discussion in the 7th patch, I have tried to do
this, see if that can make the code simpler.
Then I found out that
(1) If we would like to reuse "for_each_platform_timer" (and
"next_platform_timer") to scan the GTDT for SBSA watchdog, we have to
re-initialize acpi_gtdt_desc, too.
     So we still need to explain that why we have to re-initialize
acpi_gtdt_desc.
(2) If we totally ignore acpi_gtdt_desc, and acpi_gtdt_init(), we
can't re-use  "for_each_platform_timer" (and "next_platform_timer") .
we have to re-write  the loop of scanning the GTDT for SBSA watchdog,

So may I suggest that maybe we can keep using acpi_gtdt_init, only add
the comment to explain why we have to re-initialize
acpi_gtdt_desc(Just what you have said in the 7th patch. Thanks for
your correction for the comment, I will use that ), this way maybe can
make the code simpler.

But If you still concern about this,  we still can discuss this at -rc1.

Great thanks for your help! :-)

>
>> +     for_each_platform_timer(platform_timer) {
>> +             if (is_non_secure_watchdog(platform_timer)) {
>> +                     ret = gtdt_import_sbsa_gwdt(platform_timer, i);
>> +                     if (ret)
>> +                             break;
>> +                     i++;
>> +             }
>> +     }
>> +
>> +     if (i)
>> +             pr_info("found %d SBSA generic Watchdog(s).\n", i);
>> +
>> +     return ret;
>> +}
>> +
>> +device_initcall(gtdt_sbsa_gwdt_init);
>> --
>> 2.9.3
>>



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat