[PATCH v2 2/4] arm64: arch_timer: Introduce a generic erratum handing mechanism for fsl-a008585

[Marc Zyngier]

On 27/10/16 08:34, Ding Tianhong wrote:
> The workaround for hisilicon,161601 will check the return value of the system counter
> by different way, in order to distinguish with the fsl-a008585 workaround, introduce
> a new generic erratum handing mechanism for fsl-a008585 and rename some functions. 
> 
> v2: Introducing a new generic erratum handling mechanism for fsl erratum a008585.
> 
> Signed-off-by: Ding Tianhong <dingtianhong at huawei.com>
> ---
>  arch/arm64/include/asm/arch_timer.h  | 20 +++++++++-----
>  drivers/clocksource/arm_arch_timer.c | 51 +++++++++++++++++++++---------------
>  2 files changed, 43 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> index eaa5bbe..118719d8 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -31,15 +31,21 @@
>  
>  #if IS_ENABLED(CONFIG_FSL_ERRATUM_A008585)
>  extern struct static_key_false arch_timer_read_ool_enabled;
> -#define needs_fsl_a008585_workaround() \
> +#define needs_timer_erratum_workaround() \
>  	static_branch_unlikely(&arch_timer_read_ool_enabled)

This is too generic a name. Please make it more specific.

>  #else
> -#define needs_fsl_a008585_workaround()  false
> +#define needs_timer_erratum_workaround()  false
>  #endif
>  
> -u32 __fsl_a008585_read_cntp_tval_el0(void);
> -u32 __fsl_a008585_read_cntv_tval_el0(void);
> -u64 __fsl_a008585_read_cntvct_el0(void);
> +
> +struct arch_timer_erratum_workaround {
> +	int erratum;

What is the use of this field?

> +	u32 (*read_cntp_tval_el0)(void);
> +	u32 (*read_cntv_tval_el0)(void);
> +	u64 (*read_cntvct_el0)(void);
> +};
> +
> +extern struct arch_timer_erratum_workaround *erratum_workaround;

This is a very generic name for something that has a global visibility.
Please choose a more specific variable name.

>  
>  /*
>   * The number of retries is an arbitrary value well beyond the highest number
> @@ -62,8 +68,8 @@ u64 __fsl_a008585_read_cntvct_el0(void);
>  #define arch_timer_reg_read_stable(reg) 		\
>  ({							\
>  	u64 _val;					\
> -	if (needs_fsl_a008585_workaround())		\
> -		_val = __fsl_a008585_read_##reg();	\
> +	if (needs_timer_erratum_workaround())		\
> +		_val = erratum_workaround->read_##reg();	\

As mentioned in my initial review, you've now broken modular access to
any of the registers. Please fix it.

>  	else						\
>  		_val = read_sysreg(reg);		\
>  	_val;						\
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 73c487d..e4f7fa1 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -95,10 +95,32 @@ early_param("clocksource.arm_arch_timer.evtstrm", early_evtstrm_cfg);
>   */
>  
>  #ifdef CONFIG_FSL_ERRATUM_A008585
> +struct arch_timer_erratum_workaround *erratum_workaround = NULL;
> +
>  DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
>  EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);
>  
> -static int fsl_a008585_enable = -1;
> +
> +static u32 fsl_a008585_read_cntp_tval_el0(void)
> +{
> +	return __fsl_a008585_read_reg(cntp_tval_el0);
> +}
> +
> +static  u32 fsl_a008585_read_cntv_tval_el0(void)
> +{
> +	return __fsl_a008585_read_reg(cntv_tval_el0);
> +}
> +
> +static u64 fsl_a008585_read_cntvct_el0(void)
> +{
> +	return __fsl_a008585_read_reg(cntvct_el0);
> +}

So now that you've indirected all calls through a set of pointers, why
do you keep the __fsl_a008585_read_reg() macro inside the include file?
I don't think it has any purpose in being globally visible now.

> +
> +static struct arch_timer_erratum_workaround arch_timer_fsl_a008585 = {

And here's the proof that the erratum field is useless.

> +	.read_cntp_tval_el0 = fsl_a008585_read_cntp_tval_el0,
> +	.read_cntv_tval_el0 = fsl_a008585_read_cntv_tval_el0,
> +	.read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
> +};
>  
>  static int __init early_fsl_a008585_cfg(char *buf)
>  {
> @@ -109,26 +131,12 @@ static int __init early_fsl_a008585_cfg(char *buf)
>  	if (ret)
>  		return ret;
>  
> -	fsl_a008585_enable = val;
> +	if (val)
> +		erratum_workaround = &arch_timer_fsl_a008585;
> +
>  	return 0;
>  }
>  early_param("clocksource.arm_arch_timer.fsl-a008585", early_fsl_a008585_cfg);
> -
> -u32 __fsl_a008585_read_cntp_tval_el0(void)
> -{
> -	return __fsl_a008585_read_reg(cntp_tval_el0);
> -}
> -
> -u32 __fsl_a008585_read_cntv_tval_el0(void)
> -{
> -	return __fsl_a008585_read_reg(cntv_tval_el0);
> -}
> -
> -u64 __fsl_a008585_read_cntvct_el0(void)
> -{
> -	return __fsl_a008585_read_reg(cntvct_el0);
> -}
> -EXPORT_SYMBOL(__fsl_a008585_read_cntvct_el0);
>  #endif /* CONFIG_FSL_ERRATUM_A008585 */
>  
>  static __always_inline
> @@ -891,9 +899,10 @@ static int __init arch_timer_of_init(struct device_node *np)
>  	arch_timer_c3stop = !of_property_read_bool(np, "always-on");
>  
>  #ifdef CONFIG_FSL_ERRATUM_A008585
> -	if (fsl_a008585_enable < 0)
> -		fsl_a008585_enable = of_property_read_bool(np, "fsl,erratum-a008585");
> -	if (fsl_a008585_enable) {
> +	if (!erratum_workaround && of_property_read_bool(np, "fsl,erratum-a008585"))
> +		erratum_workaround = &arch_timer_fsl_a008585;

It used to be possible to disable the erratum workaround on the command
line, and you've just removed that feature. Please restore it.

> +
> +	if (erratum_workaround) {
>  		static_branch_enable(&arch_timer_read_ool_enabled);
>  		pr_info("Enabling workaround for FSL erratum A-008585\n");
>  	}
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...