Re: [Xen-devel] [PATCH v2 15/41] arm : acpi parse GTDT to initialize timer

[Parth Dixit <parth.dixit@xxxxxxxxxx>]

+shannon

On 24 May 2015 at 12:30, Parth Dixit <parth.dixit@xxxxxxxxxx> wrote:
>
>
> On 20 May 2015 at 23:33, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
>>
>> Hi Parth,
>>
>> On 17/05/15 21:03, Parth Dixit wrote:
>> > Parse GTDT (Generic Timer Descriptor Table) to initialize timer.
>> > Using the information presented by GTDT to initialize the arch
>> > timer (not memory-mapped).
>> >
>> > Clear all el2 fields in GTDT table after initialization
>> > for passing it to Dom0.
>> >
>> > Signed-off-by: Naresh Bhat <naresh.bhat@xxxxxxxxxx>
>> > Signed-off-by: Parth Dixit <parth.dixit@xxxxxxxxxx>
>> > ---
>> >  xen/arch/arm/acpi/boot.c   | 50
>> > ++++++++++++++++++++++++++++++++++++++++++++++
>> >  xen/arch/arm/time.c        | 38 +++++++++++++++++++++++++----------
>> >  xen/include/asm-arm/acpi.h |  2 ++
>> >  3 files changed, 79 insertions(+), 11 deletions(-)
>> >
>> > diff --git a/xen/arch/arm/acpi/boot.c b/xen/arch/arm/acpi/boot.c
>> > index 7d9758f..a8311ae 100644
>> > --- a/xen/arch/arm/acpi/boot.c
>> > +++ b/xen/arch/arm/acpi/boot.c
>> > @@ -30,6 +30,8 @@
>> >
>> >  #include <asm/acpi.h>
>> >  #include <asm/smp.h>
>> > +#include <asm/irq.h>
>> > +#include <asm/time.h>
>> >
>> >  /* Processors with enabled flag and sane MPIDR */
>> >  static int enabled_cpus;
>> > @@ -40,6 +42,54 @@ static bool_t __initdata bootcpu_valid;
>> >  /* arch-optional setting to enable display of offline cpus >=
>> > nr_cpu_ids */
>> >  static unsigned int total_cpus = 0;
>> >
>> > +/* Initialize per-processor generic timer */
>> > +void __init acpi_preinit_xen_time(unsigned int generic_timer_irq[])
>>
>> acpi/boot.c begin to be a junk room for all ACPI code. It would have
>> been more logic to have this code in arch/arm/time.c with proper #ifdef.
>>
>> This would have drop the generic_timer_irq which is difficult to
>> understand.
>>
>> > +{
>> > +    int type;
>> > +    struct acpi_table_gtdt *gtdt=NULL;
>>
>> *gtdt = NULL;
>>
>> > +    u8 checksum;
>> > +    static const int GTDT_INTRL_TAB[] =
>>
>> all uppercase name are used for define.
>>
>> > +    {
>> > +        ACPI_IRQ_TYPE_LEVEL_HIGH,
>> > +        ACPI_IRQ_TYPE_EDGE_RISING,
>> > +        ACPI_IRQ_TYPE_LEVEL_LOW,
>> > +        ACPI_IRQ_TYPE_EDGE_FALLING
>> > +    };
>>
>> It took me a while to understand how this work.
>>
>> I would prefer an helper which check each field and return/set the
>> correct interrupt type.
>>
>> > +
>> > +    acpi_get_table(ACPI_SIG_GTDT, 0, (struct acpi_table_header
>> > **)&gtdt);
>> > +
>> > +    if( gtdt )
>> > +    {
>>
>> If gtdt is NULL you will continue without any warning and potentially
>> crash later.
>>
>> Also please do:
>>
>> if ( !gtdt ) {
>>   /* handle error */
>>   return;
>> }
>>
>> /* setup the timer */
>>
>> It's easier to understand and remove one indentation.
>>
>> > +        /* Initialize all the generic timer IRQ variable from GTDT
>> > table */
>> > +
>> > +        type = GTDT_INTRL_TAB[gtdt->non_secure_el1_flags &
>> > ACPI_GTDT_INTR_MASK];
>> > +        set_irq_type(gtdt->non_secure_el1_interrupt, type);
>> > +        generic_timer_irq[TIMER_PHYS_NONSECURE_PPI] =
>> > +            gtdt->non_secure_el1_interrupt;
>> > +
>> > +        type = GTDT_INTRL_TAB[gtdt->secure_el1_flags &
>> > ACPI_GTDT_INTR_MASK];
>> > +        set_irq_type(gtdt->secure_el1_interrupt, type);
>> > +        generic_timer_irq[TIMER_PHYS_SECURE_PPI] =
>> > +            gtdt->secure_el1_interrupt;
>> > +
>> > +        type = GTDT_INTRL_TAB[gtdt->non_secure_el2_flags &
>> > ACPI_GTDT_INTR_MASK];
>> > +        set_irq_type(gtdt->non_secure_el2_interrupt, type);
>> > +        generic_timer_irq[TIMER_HYP_PPI] =
>> > +            gtdt->non_secure_el2_interrupt;
>> > +
>> > +        type = GTDT_INTRL_TAB[gtdt->virtual_timer_flags &
>> > ACPI_GTDT_INTR_MASK];
>> > +        set_irq_type(gtdt->virtual_timer_interrupt, type);
>> > +        generic_timer_irq[TIMER_VIRT_PPI] =
>> > +            gtdt->virtual_timer_interrupt;
>> > +
>> > +        gtdt->non_secure_el2_interrupt = 0;
>> > +        gtdt->non_secure_el2_flags = 0;
>> > +        checksum = acpi_tb_checksum(ACPI_CAST_PTR(u8, gtdt),
>> > gtdt->header.length);
>> > +        gtdt->header.checksum -= checksum;
>> > +        clean_dcache_va_range(gtdt, sizeof(struct acpi_table_gtdt));
>>
>> Similar comment as on the MADT, this function is initializing the timer
>> and not modifying the ACPI table.
>>
>> I would prefer a separate function which is called during DOM0 building.
>> It would be easier to know how the ACPI table has been modified for DOM0.
>>
>> Also, please add a comment to explain this block smth like /* Hide EL2
>> interrupt to DOM0 */. Maybe explaining that the table is re-used.
>>
>> Furthermore, are you sure that the ACPI table will always be in R/W
>> memory? If not, we should duplicate the table and update the field.
>>
>> > +    }
>> > +}
>> > +
>> >  /*
>> >   * acpi_map_gic_cpu_interface - generates a logical cpu number
>> >   * and map to MPIDR represented by GICC structure
>> > diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
>> > index ce6d3fd..bff95ab 100644
>> > --- a/xen/arch/arm/time.c
>> > +++ b/xen/arch/arm/time.c
>> > @@ -29,6 +29,7 @@
>> >  #include <xen/time.h>
>> >  #include <xen/sched.h>
>> >  #include <xen/event.h>
>> > +#include <xen/acpi.h>
>> >  #include <asm/system.h>
>> >  #include <asm/time.h>
>> >  #include <asm/gic.h>
>> > @@ -64,7 +65,7 @@ unsigned int timer_get_irq(enum timer_ppi ppi)
>> >  static __initdata struct dt_device_node *timer;
>> >
>> >  /* Set up the timer on the boot CPU (early init function) */
>> > -void __init preinit_xen_time(void)
>> > +static void __init dt_preinit_xen_time(void)
>> >  {
>> >      static const struct dt_device_match timer_ids[] __initconst =
>> >      {
>> > @@ -72,7 +73,6 @@ void __init preinit_xen_time(void)
>> >          { /* sentinel */ },
>> >      };
>> >      int res;
>> > -    u32 rate;
>> >
>> >      timer = dt_find_matching_node(NULL, timer_ids);
>> >      if ( !timer )
>> > @@ -84,8 +84,21 @@ void __init preinit_xen_time(void)
>> >      if ( res )
>> >          panic("Timer: Cannot initialize platform timer");
>> >
>> > -    res = dt_property_read_u32(timer, "clock-frequency", &rate);
>> > -    if ( res )
>> > +}
>> > +
>> > +
>> > +
>>
>> Only one blank line is enough.
>>
>> > +void __init preinit_xen_time(void)
>> > +{
>> > +    u32 rate;
>> > +
>> > +    /* Initialize all the generic timers presented in GTDT */
>> > +    if ( acpi_disabled )
>> > +        dt_preinit_xen_time();
>> > +    else
>> > +        acpi_preinit_xen_time(timer_irq);
>> > +
>> > +    if( acpi_disabled && dt_property_read_u32(timer, "clock-frequency",
>> > &rate) )
>>
>> A such check calls for more refactoring...
>>
>> >          cpu_khz = rate / 1000;
>> >      else
>> >          cpu_khz = READ_SYSREG32(CNTFRQ_EL0) / 1000;
>>
>> Duplicating this line wouldn't have been too bad compare to the check.
>>
>> > @@ -99,14 +112,17 @@ int __init init_xen_time(void)
>> >      int res;
>> >      unsigned int i;
>> >
>> > -    /* Retrieve all IRQs for the timer */
>> > -    for ( i = TIMER_PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++ )
>> > +    if( acpi_disabled )
>> >      {
>> > -        res = platform_get_irq(timer, i);
>> > -
>> > -        if ( res < 0 )
>> > -            panic("Timer: Unable to retrieve IRQ %u from the device
>> > tree", i);
>> > -        timer_irq[i] = res;
>> > +        /* Retrieve all IRQs for the timer */
>> > +        for ( i = TIMER_PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++ )
>> > +        {
>> > +            res = platform_get_irq(timer, i);
>> > +
>> > +            if ( res < 0 )
>> > +                panic("Timer: Unable to retrieve IRQ %u from the device
>> > tree", i);
>> > +            timer_irq[i] = res;
>> > +        }
>>
>> Another helper for this device tree code?
>>
>> >      }
>> >
>> >      /* Check that this CPU supports the Generic Timer interface */
>> > diff --git a/xen/include/asm-arm/acpi.h b/xen/include/asm-arm/acpi.h
>> > index 1767143..482cc5b 100644
>> > --- a/xen/include/asm-arm/acpi.h
>> > +++ b/xen/include/asm-arm/acpi.h
>> > @@ -36,10 +36,12 @@ bool_t acpi_psci_present(void);
>> >  /* 1 to indicate HVC is present instead of SMC as the PSCI conduit */
>> >  bool_t acpi_psci_hvc_present(void);
>> >  void __init acpi_init_cpus(void);
>> > +void __init acpi_preinit_xen_time(unsigned int generic_timer_irq[]);
>> >  #else
>> >  static inline bool_t acpi_psci_present(void) { return false; }
>> >  static inline bool_t acpi_psci_hvc_present(void) {return false; }
>> >  static inline void acpi_init_cpus(void) { }
>> > +static inline void acpi_preinit_xen_time(unsigned int
>> > generic_timer_irq[]){ }
>> >  #endif /* CONFIG_ACPI */
>> >
>> >  /* Basic configuration for ACPI */
>> >
>>
> sure, will take care in next patchset.
>>
>> Regards,
>>
>> --
>> Julien Grall
>
>

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