Date:   Tue, 18 Apr 2017 18:21:07 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     fu.wei@...aro.org
Cc:     rjw@...ysocki.net, lenb@...nel.org, daniel.lezcano@...aro.org,
        tglx@...utronix.de, marc.zyngier@....com, mark.rutland@....com,
        sudeep.holla@....com, hanjun.guo@...aro.org,
        linux-arm-kernel@...ts.infradead.org, linaro-acpi@...ts.linaro.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        rruigrok@...eaurora.org, harba@...eaurora.org, cov@...eaurora.org,
        timur@...eaurora.org, graeme.gregory@...aro.org,
        al.stone@...aro.org, jcm@...hat.com, wei@...hat.com, arnd@...db.de,
        catalin.marinas@....com, will.deacon@....com,
        Suravee.Suthikulpanit@....com, leo.duran@....com, wim@...ana.be,
        linux@...ck-us.net, linux-watchdog@...r.kernel.org,
        tn@...ihalf.com, christoffer.dall@...aro.org, julien.grall@....com
Subject: Re: [PATCH v24 09/11] acpi/arm64: Add memory-mapped timer support in
 GTDT driver

On Sat, Apr 15, 2017 at 02:40:12AM +0800, fu.wei@...aro.org wrote:
> From: Fu Wei <fu.wei@...aro.org>
> 
> 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@...aro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> ---
>  drivers/acpi/arm64/gtdt.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h      |   1 +
>  2 files changed, 145 insertions(+)
> 
> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
> index 3d95af8..c9ef9c2 100644
> --- a/drivers/acpi/arm64/gtdt.c
> +++ b/drivers/acpi/arm64/gtdt.c
> @@ -13,6 +13,7 @@
>  
>  #include <linux/acpi.h>
>  #include <linux/init.h>
> +#include <linux/irqdomain.h>
>  #include <linux/kernel.h>
>  
>  #include <clocksource/arm_arch_timer.h>
> @@ -37,6 +38,28 @@ struct acpi_gtdt_descriptor {
>  
>  static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
>  
> +static inline void *next_platform_timer(void *platform_timer)
> +{
> +	struct acpi_gtdt_header *gh = platform_timer;
> +
> +	platform_timer += gh->length;
> +	if (platform_timer < acpi_gtdt_desc.gtdt_end)
> +		return platform_timer;
> +
> +	return NULL;
> +}
> +
> +#define for_each_platform_timer(_g)				\
> +	for (_g = acpi_gtdt_desc.platform_timer; _g;	\
> +	     _g = next_platform_timer(_g))
> +
> +static inline bool is_timer_block(void *platform_timer)
> +{
> +	struct acpi_gtdt_header *gh = platform_timer;
> +
> +	return gh->type == ACPI_GTDT_TYPE_TIMER_BLOCK;
> +}
> +
>  static int __init map_gt_gsi(u32 interrupt, u32 flags)
>  {
>  	int trigger, polarity;
> @@ -155,3 +178,124 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>  
>  	return 0;
>  }
> +
> +static int __init gtdt_parse_timer_block(struct acpi_gtdt_timer_block *block,
> +					 struct arch_timer_mem *timer_mem)
> +{
> +	int i;
> +	struct arch_timer_mem_frame *frame;
> +	struct acpi_gtdt_timer_entry *gtdt_frame;
> +
> +	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;
> +	}
> +
> +	timer_mem->cntctlbase = (phys_addr_t)block->block_address;
> +	/*
> +	 * The CNTCTLBase frame is 4KB (register offsets 0x000 - 0xFFC).
> +	 * See ARM DDI 0487A.k_iss10775, page I1-5129, Table I1-3
> +	 * "CNTCTLBase memory map".
> +	 */
> +	timer_mem->size = SZ_4K;
> +
> +	gtdt_frame = (void *)block + block->timer_offset;
> +	if (gtdt_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++, gtdt_frame++) {
> +		if (gtdt_frame->common_flags & ACPI_GTDT_GT_IS_SECURE_TIMER)
> +			continue;
> +
> +		if (!gtdt_frame->base_address || !gtdt_frame->timer_interrupt)
> +			goto error;
> +
> +		frame = &timer_mem->frame[gtdt_frame->frame_number];
> +		frame->phys_irq = map_gt_gsi(gtdt_frame->timer_interrupt,
> +					     gtdt_frame->timer_flags);
> +		if (frame->phys_irq <= 0) {
> +			pr_warn("failed to map physical timer irq in frame %d.\n",
> +				gtdt_frame->frame_number);
> +			goto error;
> +		}
> +
> +		if (gtdt_frame->virtual_timer_interrupt) {
> +			frame->virt_irq =
> +				map_gt_gsi(gtdt_frame->virtual_timer_interrupt,
> +					   gtdt_frame->virtual_timer_flags);
> +			if (frame->virt_irq <= 0) {
> +				pr_warn("failed to map virtual timer irq in frame %d.\n",
> +					gtdt_frame->frame_number);
> +				goto error;
> +			}
> +		} else {
> +			frame->virt_irq = 0;
> +			pr_debug("virtual timer in frame %d not implemented.\n",
> +				 gtdt_frame->frame_number);
> +		}
> +
> +		frame->cntbase = gtdt_frame->base_address;
> +		/*
> +		 * The CNTBaseN frame is 4KB (register offsets 0x000 - 0xFFC).
> +		 * See ARM DDI 0487A.k_iss10775, page I1-5130, Table I1-4
> +		 * "CNTBaseN memory map".
> +		 */
> +		frame->size = SZ_4K;
> +		frame->valid = true;
> +	}
> +
> +	return 0;
> +
> +error:
> +	for (i = 0; i < ARCH_TIMER_MEM_MAX_FRAMES; i++) {
> +		frame = &timer_mem->frame[i];
> +		if (frame->phys_irq > 0)
> +			acpi_unregister_irq(frame->phys_irq);
> +		if (frame->virt_irq > 0)
> +			acpi_unregister_irq(frame->virt_irq);
> +	}

There are three error paths, none of them reset [i,gtdt_frame],
correct ?

If yes, why can't it simply be written like this ?

for (; i >= 0; i--, gtdt_frame--) {
	frame = &timer_mem->frame[gtdt_frame->frame_number];

	/* not sure this check is actually needed */
	if (gtdt_frame->common_flags & ACPI_GTDT_GT_IS_SECURE_TIMER)
		continue;

	if (frame->phys_irq > 0)
		acpi_unregister_gsi(gtdt_frame->timer_interrupt);
	if (frame->virt_irq > 0)
		acpi_unregister_gsi(gtdt_frame->virtual_timer_interrupt);
}

It is time we merged this code, that's for certain so if for any reason
loop above does not work this current series is ok for me, go ahead, I
just don't see the point of adding another ACPI IRQ function
acpi_unregister_irq() (which does not mean acpi_unregister_gsi() is sane
- we just lived with it when ACPI ARM64 was merged because changing its
API requires reworking x86 legacy code that I don't understand).

Thanks,
Lorenzo

> +	return -EINVAL;
> +}
> +
> +/**
> + * acpi_arch_timer_mem_init() - Get the info of all GT blocks in GTDT table.
> + * @timer_mem:	The pointer to the array of struct arch_timer_mem for returning
> + *		the result of parsing. The element number of this array should
> + *		be platform_timer_count(the total number of platform timers).
> + * @timer_count: It points to a integer variable which is used for storing the
> + *		number of GT blocks we have parsed.
> + *
> + * Return: 0 if success, -EINVAL/-ENODEV if error.
> + */
> +int __init acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem,
> +				    int *timer_count)
> +{
> +	int ret;
> +	void *platform_timer;
> +
> +	*timer_count = 0;
> +	for_each_platform_timer(platform_timer) {
> +		if (is_timer_block(platform_timer)) {
> +			ret = gtdt_parse_timer_block(platform_timer, timer_mem);
> +			if (ret)
> +				return ret;
> +			timer_mem++;
> +			(*timer_count)++;
> +		}
> +	}
> +
> +	if (*timer_count)
> +		pr_info("found %d memory-mapped timer block(s).\n",
> +			*timer_count);
> +
> +	return 0;
> +}
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 728d1ed..4b1ab65 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -606,6 +606,7 @@ int acpi_reconfig_notifier_unregister(struct notifier_block *nb);
>  int acpi_gtdt_init(struct acpi_table_header *table, int *platform_timer_count);
>  int acpi_gtdt_map_ppi(int type);
>  bool acpi_gtdt_c3stop(int type);
> +int acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem, int *timer_count);
>  #endif
>  
>  #else	/* !CONFIG_ACPI */
> -- 
> 2.9.3
> 

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