Re: [PATCH v8 7/9] acpi/arm64: Add memory-mapped timer support in GTDT driver

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Wed, Jul 20, 2016 at 02:18:02AM +0800, fu.wei@linaro.org wrote:
> From: Fu Wei <fu.wei@linaro.org>
> 
> This driver adds support for parsing memory-mapped timer in GTDT:
> provide a kernel APIs to parse GT Block Structure in GTDT,
> export all the info by filling the struct which provided
> by parameter(pointer of the struct).
> 
> By this driver, we can add ACPI support for memory-mapped timer in
> arm_arch_timer drivers, and separate the ACPI GTDT knowledge from it.

"On platforms booting with ACPI, architected memory 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@linaro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> ---
>  drivers/acpi/arm64/acpi_gtdt.c       | 72 ++++++++++++++++++++++++++++++++++++
>  include/clocksource/arm_arch_timer.h | 15 ++++++++
>  include/linux/acpi.h                 |  1 +
>  3 files changed, 88 insertions(+)
> 
> diff --git a/drivers/acpi/arm64/acpi_gtdt.c b/drivers/acpi/arm64/acpi_gtdt.c
> index e1cfc9e..b48e443 100644
> --- a/drivers/acpi/arm64/acpi_gtdt.c
> +++ b/drivers/acpi/arm64/acpi_gtdt.c
> @@ -150,3 +150,75 @@ int __init acpi_gtdt_init(struct acpi_table_header *table)
>  
>  	return gtdt->platform_timer_count;
>  }
> +
> +static int __init gtdt_parse_gt_block(void *platform_timer,
> +				      struct gt_block_data *data)
> +{

Nit: you can directly pass a struct acpi_gtdt_timer_block* pointer.

> +	struct acpi_gtdt_timer_block *block = platform_timer;
> +	struct acpi_gtdt_timer_entry *frame;
> +	int i;
> +
> +	if (!block || !data)
> +		return -EINVAL;
> +
> +	if (!block->block_address || !block->timer_count)
> +		goto error;

Here we jump to print an error and bail out. The only reason
why we need a goto is to print a common error message and that's
exactly what we do _not_ need, if there is a FW error we want
to understand which one is that, otherwise the information you
are printing is useless for debugging (provided we can make use
of this info, which is questionable anyway).

> +	data->cntctlbase_phy = (phys_addr_t)block->block_address;
> +	data->timer_count = block->timer_count;
> +
> +	frame = (void *)block + block->timer_offset;
> +	if (frame + block->timer_count != (void *)block + block->header.length)
> +		goto error;

See above.

> +	/*
> +	 * Get the GT timer Frame data for every GT Block Timer
> +	 */
> +	for (i = 0; i < block->timer_count; i++) {
> +		frame += i;

This is wrong, if you have multiple frames, pointers would add up and
that's not correct.

> +		if (!frame->base_address || !frame->timer_interrupt)
> +			goto error;

See above.

> +		data->timer[i].frame_nr = frame->frame_number;
> +		data->timer[i].cntbase_phy = frame->base_address;
> +		data->timer[i].irq =
> +			map_generic_timer_interrupt(frame->timer_interrupt,
> +						    frame->timer_flags);

AFAIK map_generic_timer_interrupt() may fail, you should cater for that.

> +		if (frame->virtual_timer_interrupt)
> +			data->timer[i].virt_irq =
> +				map_generic_timer_interrupt(
> +					frame->virtual_timer_interrupt,
> +					frame->virtual_timer_flags);

Ditto.

> +	}
> +	return 0;
> +
> +error:
> +	pr_err(FW_BUG "invalid GT Block data.\n");
> +	return -EINVAL;

See above.

> +}
> +
> +/*
> + * Get the GT block info for memory-mapped timer from GTDT table.
> + * Please make sure we have called acpi_gtdt_init, because it helps to
> + * init the global variables.

I already commented on this. I think the second part of this comment
is useless (it is a function with one caller, make sure you respect
the calling sequence and be done with this).

Thanks,
Lorenzo

> + */
> +int __init gtdt_arch_timer_mem_init(struct gt_block_data *data)
> +{
> +	void *platform_timer;
> +	int index = 0;
> +	int ret;
> +
> +	for_each_platform_timer(platform_timer) {
> +		if (!is_timer_block(platform_timer))
> +			continue;
> +		ret = gtdt_parse_gt_block(platform_timer, data + index);
> +		if (ret)
> +			return ret;
> +		index++;
> +	}
> +
> +	if (index)
> +		pr_info("found %d memory-mapped timer block(s).\n", index);
> +
> +	return index;
> +}
> diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
> index 16dcd10..ece6b3b 100644
> --- a/include/clocksource/arm_arch_timer.h
> +++ b/include/clocksource/arm_arch_timer.h
> @@ -56,6 +56,8 @@ enum spi_nr {
>  #define ARCH_TIMER_MEM_PHYS_ACCESS	2
>  #define ARCH_TIMER_MEM_VIRT_ACCESS	3
>  
> +#define ARCH_TIMER_MEM_MAX_FRAME	8
> +
>  #define ARCH_TIMER_USR_PCT_ACCESS_EN	(1 << 0) /* physical counter */
>  #define ARCH_TIMER_USR_VCT_ACCESS_EN	(1 << 1) /* virtual counter */
>  #define ARCH_TIMER_VIRT_EVT_EN		(1 << 2)
> @@ -71,6 +73,19 @@ struct arch_timer_kvm_info {
>  	int virtual_irq;
>  };
>  
> +struct gt_timer_data {
> +	int frame_nr;
> +	phys_addr_t cntbase_phy;
> +	int irq;
> +	int virt_irq;
> +};
> +
> +struct gt_block_data {
> +	phys_addr_t cntctlbase_phy;
> +	int timer_count;
> +	struct gt_timer_data timer[ARCH_TIMER_MEM_MAX_FRAME];
> +};
> +
>  #ifdef CONFIG_ARM_ARCH_TIMER
>  
>  extern u32 arch_timer_get_rate(void);
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index fb8b689..24b1750 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -536,6 +536,7 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *);
>  int acpi_gtdt_init(struct acpi_table_header *table);
>  int acpi_gtdt_map_ppi(int type);
>  bool acpi_gtdt_c3stop(void);
> +int gtdt_arch_timer_mem_init(struct gt_block_data *data);
>  #endif
>  
>  #else	/* !CONFIG_ACPI */
> -- 
> 2.5.5
>