Re: [RFC part3 PATCH 1/2] clocksource / arch_timer: Use ACPI GTDT table to initialize arch timer

Rob Herring
2013-12-04T15:33:38Z

On Tue, Dec 3, 2013 at 5:15 AM, Hanjun Guo <hanjun.guo@linaro.org> wrote:
> ACPI GTDT (Generic Timer Description Table) contains information for
> arch timer initialization, this patch use this table to probe arm timer.
>
> GTDT table is used for ARM/ARM64 only, please refer to chapter 5.2.24
> of ACPI 5.0 spec for detailed inforamtion
>
> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> ---
> drivers/clocksource/arm_arch_timer.c | 129 ++++++++++++++++++++++++++++++----
> include/clocksource/arm_arch_timer.h | 7 +-
> 2 files changed, 120 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 95fb944..c968041 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -21,6 +21,7 @@
> #include <linux/io.h>
> #include <linux/slab.h>
> #include <linux/sched_clock.h>
> +#include <linux/acpi.h>
>
> #include <asm/arch_timer.h>
> #include <asm/virt.h>
> @@ -632,20 +633,8 @@ static void __init arch_timer_common_init(void)
> arch_timer_arch_init();
> }
>
> -static void __init arch_timer_init(struct device_node *np)
> +static void __init arch_timer_init(void)
> {
> - int i;
> -
> - if (arch_timers_present & ARCH_CP15_TIMER) {
> - pr_warn("arch_timer: multiple nodes in dt, skipping\n");
> - return;
> - }
> -
> - arch_timers_present |= ARCH_CP15_TIMER;
> - for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
> - arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
> - arch_timer_detect_rate(NULL, np);
> -
> /*
> * If HYP mode is available, we know that the physical timer
> * has been configured to be accessible from PL1. Use it, so
> @@ -667,8 +656,118 @@ static void __init arch_timer_init(struct device_node *np)
> arch_timer_register();
> arch_timer_common_init();
> }
> -CLOCKSOURCE_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer", arch_timer_init);
> -CLOCKSOURCE_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer", arch_timer_init);
> +
> +static void __init arch_timer_of_init(struct device_node *np)
> +{
> + int i;
> +
> + if (arch_timers_present & ARCH_CP15_TIMER) {
> + pr_warn("arch_timer: multiple nodes in dt, skipping\n");
> + return;
> + }
> +
> + arch_timers_present |= ARCH_CP15_TIMER;
> + for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
> + arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
> + arch_timer_detect_rate(NULL, np);
> +
> + arch_timer_init();
> +}
> +CLOCKSOURCE_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer", arch_timer_of_init);
> +CLOCKSOURCE_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer", arch_timer_of_init);
> +
> +#ifdef CONFIG_ACPI
> +void __init arch_timer_acpi_init(void)
> +{
> + struct acpi_table_gtdt *gtdt;
> + acpi_size tbl_size;
> + int trigger, polarity;
> + void __iomem *base = NULL;
> +
> + if (acpi_disabled)

Wouldn't the core ACPI code never call this function if ACPI is disabled?

> + return;
> +
> + if (arch_timers_present & ARCH_CP15_TIMER) {
> + pr_warn("arch_timer: already initialized, skipping\n");
> + return;
> + }
> +
> + if (ACPI_FAILURE(acpi_get_table_with_size(ACPI_SIG_GTDT, 0,
> + (struct acpi_table_header **)&gtdt, &tbl_size))) {
> + pr_err("arch_timer: GTDT table not defined\n");
> + return;
> + }
> +
> + arch_timers_present |= ARCH_CP15_TIMER;

So you have marked the timer as initialized, but then may fail on
error later on here.

> +
> + /*
> + * Get the timer frequency. Since there is no frequency info
> + * in the GTDT table, so we should read it from CNTFREG register
> + * or hard code here to wait for the new ACPI spec available.
> + */
> + if (!gtdt->address) {
> + arch_timer_rate = arch_timer_get_cntfrq();
> + } else {
> + base = ioremap(gtdt->address, CNTFRQ);
> + if (!base) {
> + pr_warn("arch_timer: unable to map arch timer base address\n");
> + return;
> + }
> +
> + arch_timer_rate = readl_relaxed(base + CNTFRQ);
> + iounmap(base);

This is for memory mapped timer? If so, then isn't setting
ARCH_CP15_TIMER the wrong thing to do?

> + }
> +
> + if (!arch_timer_rate) {
> + /* Hard code here to set frequence ? */
> + pr_warn("arch_timer: Could not get frequency from GTDT table or CNTFREG\n");
> + }
> +
> + if (gtdt->secure_pl1_interrupt) {

Really, I think the kernel should just ignore the secure interrupt.
The DT code has the same issue, but that doesn't affect the code size.

> + trigger = (gtdt->secure_pl1_flags & ACPI_GTDT_INTERRUPT_MODE) ?
> + ACPI_EDGE_SENSITIVE : ACPI_LEVEL_SENSITIVE;

Why not use the already defined linux irq trigger types here and make
acpi_register_gsi use them?

> + polarity =
> + (gtdt->secure_pl1_flags & ACPI_GTDT_INTERRUPT_POLARITY)
> + ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
> + arch_timer_ppi[0] = acpi_register_gsi(NULL,
> + gtdt->secure_pl1_interrupt, trigger, polarity);
> + }
> + if (gtdt->non_secure_pl1_interrupt) {
> + trigger =
> + (gtdt->non_secure_pl1_flags & ACPI_GTDT_INTERRUPT_MODE)
> + ? ACPI_EDGE_SENSITIVE : ACPI_LEVEL_SENSITIVE;
> + polarity =
> + (gtdt->non_secure_pl1_flags & ACPI_GTDT_INTERRUPT_POLARITY)
> + ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
> + arch_timer_ppi[1] = acpi_register_gsi(NULL,
> + gtdt->non_secure_pl1_interrupt, trigger, polarity);
> + }
> + if (gtdt->virtual_timer_interrupt) {
> + trigger = (gtdt->virtual_timer_flags & ACPI_GTDT_INTERRUPT_MODE)
> + ? ACPI_EDGE_SENSITIVE : ACPI_LEVEL_SENSITIVE;
> + polarity =
> + (gtdt->virtual_timer_flags & ACPI_GTDT_INTERRUPT_POLARITY)
> + ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
> + arch_timer_ppi[2] = acpi_register_gsi(NULL,
> + gtdt->virtual_timer_interrupt, trigger, polarity);
> + }
> + if (gtdt->non_secure_pl2_interrupt) {
> + trigger =
> + (gtdt->non_secure_pl2_flags & ACPI_GTDT_INTERRUPT_MODE)
> + ? ACPI_EDGE_SENSITIVE : ACPI_LEVEL_SENSITIVE;
> + polarity =
> + (gtdt->non_secure_pl2_flags & ACPI_GTDT_INTERRUPT_POLARITY)
> + ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
> + arch_timer_ppi[3] = acpi_register_gsi(NULL,
> + gtdt->non_secure_pl2_interrupt, trigger, polarity);
> + }
> +
> + early_acpi_os_unmap_memory(gtdt, tbl_size);

Who did the mapping? acpi_get_table_with_size? I think the core code
should handle the mapping and unmapping of ACPI tables. We don't want
to have to duplicate this in every initialization function. This seems
error prone.

Rob