linux-kernel - Re: [PATCH] MIPS: cevt-r4k: Enable intimer for Loongson64 CPUs with extimer

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Date:   Sun, 04 Oct 2020 22:49:55 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     linux-mips@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        WANG Xuerui <git@...0n.name>,
        Paul Burton <paulburton@...nel.org>,
        周琰杰 <zhouyanjie@...yeetech.com>,
        afzal mohammed <afzal.mohd.ma@...il.com>,
        Liangliang Huang <huanglllzu@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: cevt-r4k: Enable intimer for Loongson64 CPUs with
 extimer

Hi,

Le mer. 23 sept. 2020 à 19:02, Jiaxun Yang <jiaxun.yang@...goat.com> a 
écrit :
> Loongson64C and Loongson64G have extimer feature, which is a
> timer sharing Cause.TI with cevt-r4k (named intimer).
> 
> To ensure the cevt-r4k's usability, we need to add a callback for
> clock device to switch intimer.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
> ---
>  arch/mips/include/asm/cpu-features.h |  4 ++++
>  arch/mips/include/asm/cpu.h          |  1 +
>  arch/mips/kernel/cevt-r4k.c          | 25 +++++++++++++++++++++++++
>  arch/mips/kernel/cpu-probe.c         |  6 +++++-
>  4 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/mips/include/asm/cpu-features.h 
> b/arch/mips/include/asm/cpu-features.h
> index 78cf7e300f12..aec458eee2a5 100644
> --- a/arch/mips/include/asm/cpu-features.h
> +++ b/arch/mips/include/asm/cpu-features.h
> @@ -576,6 +576,10 @@
>  # define cpu_has_gsexcex	__opt(MIPS_CPU_GSEXCEX)
>  #endif
> 
> +#ifndef cpu_has_extimer
> +# define cpu_has_extimer	__opt(MIPS_CPU_EXTIMER)
> +#endif
> +
>  #ifdef CONFIG_SMP
>  /*
>   * Some systems share FTLB RAMs between threads within a core 
> (siblings in
> diff --git a/arch/mips/include/asm/cpu.h b/arch/mips/include/asm/cpu.h
> index 388a82f28a87..854e1b44254b 100644
> --- a/arch/mips/include/asm/cpu.h
> +++ b/arch/mips/include/asm/cpu.h
> @@ -429,6 +429,7 @@ enum cpu_type_enum {
>  #define MIPS_CPU_MAC_2008_ONLY	BIT_ULL(60)	/* CPU Only support 
> MAC2008 Fused multiply-add instruction */
>  #define MIPS_CPU_FTLBPAREX	BIT_ULL(61)	/* CPU has FTLB parity 
> exception */
>  #define MIPS_CPU_GSEXCEX	BIT_ULL(62)	/* CPU has GSExc exception */
> +#define MIPS_CPU_EXTIMER	BIT_ULL(63)	/* CPU has External Timer 
> (Loongson) */
> 
>  /*
>   * CPU ASE encodings
> diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c
> index 995ad9e69ded..fae49e9215b4 100644
> --- a/arch/mips/kernel/cevt-r4k.c
> +++ b/arch/mips/kernel/cevt-r4k.c
> @@ -15,6 +15,8 @@
> 
>  #include <asm/time.h>
>  #include <asm/cevt-r4k.h>
> +#include <asm/cpu-features.h>
> +#include <asm/mipsregs.h>
> 
>  static int mips_next_event(unsigned long delta,
>  			   struct clock_event_device *evt)
> @@ -294,6 +296,24 @@ core_initcall(r4k_register_cpufreq_notifier);
> 
>  #endif /* !CONFIG_CPU_FREQ */
> 
> +#ifdef CONFIG_CPU_LOONGSON64
> +static int c0_compare_int_enable(struct clock_event_device *cd)
> +{
> +	if (cpu_has_extimer)
> +		set_c0_config6(LOONGSON_CONF6_INTIMER);
> +
> +	return 0;
> +}
> +
> +static int c0_compare_int_disable(struct clock_event_device *cd)
> +{
> +	if (cpu_has_extimer)
> +		clear_c0_config6(LOONGSON_CONF6_INTIMER);
> +
> +	return 0;
> +}
> +#endif

static int __maybe_unused c0_compare_int_enable(...)
{
    ...
}

without the #ifdef.

Or better, move these two to loongson64 board code, with "extern int 
c0_compare_int_enable" in a header somewhere.

> +
>  int r4k_clockevent_init(void)
>  {
>  	unsigned long flags = IRQF_PERCPU | IRQF_TIMER | IRQF_SHARED;
> @@ -329,6 +349,11 @@ int r4k_clockevent_init(void)
>  	cd->set_next_event	= mips_next_event;
>  	cd->event_handler	= mips_event_handler;
> 
> +#ifdef CONFIG_CPU_LOONGSON64
> +	cd->set_state_oneshot = c0_compare_int_enable;
> +	cd->set_state_shutdown = c0_compare_int_disable;
> +#endif
> +

if (IS_ENABLED(CONFIG_CPU_LOONGSON64)) {
    cd->set_state_oneshot = ...;
}

Although I think this is still incorrect: here you check whether the 
kernel supports this CPU, instead of checking what CPU you're running 
on.

Cheers,
-Paul

>  	clockevents_config_and_register(cd, mips_hpt_frequency, min_delta, 
> 0x7fffffff);
> 
>  	if (cp0_timer_irq_installed)
> diff --git a/arch/mips/kernel/cpu-probe.c 
> b/arch/mips/kernel/cpu-probe.c
> index 6be23f205e74..4f1e9ef2644e 100644
> --- a/arch/mips/kernel/cpu-probe.c
> +++ b/arch/mips/kernel/cpu-probe.c
> @@ -2030,6 +2030,9 @@ static inline void decode_cpucfg(struct 
> cpuinfo_mips *c)
>  	if (cfg2 & LOONGSON_CFG2_LEXT2)
>  		c->ases |= MIPS_ASE_LOONGSON_EXT2;
> 
> +	if (cfg2 & LOONGSON_CFG2_LLFTP)
> +		c->options |= MIPS_CPU_EXTIMER;
> +
>  	if (cfg2 & LOONGSON_CFG2_LSPW) {
>  		c->options |= MIPS_CPU_LDPTE;
>  		c->guest.options |= MIPS_CPU_LDPTE;
> @@ -2088,7 +2091,8 @@ static inline void cpu_probe_loongson(struct 
> cpuinfo_mips *c, unsigned int cpu)
>  		 * Also some early Loongson-3A2000 had wrong TLB type in Config
>  		 * register, we correct it here.
>  		 */
> -		c->options |= MIPS_CPU_FTLB | MIPS_CPU_TLBINV | MIPS_CPU_LDPTE;
> +		c->options |= MIPS_CPU_FTLB | MIPS_CPU_TLBINV | MIPS_CPU_LDPTE |
> +			      MIPS_CPU_EXTIMER;
>  		c->writecombine = _CACHE_UNCACHED_ACCELERATED;
>  		c->ases |= (MIPS_ASE_LOONGSON_MMI | MIPS_ASE_LOONGSON_CAM |
>  			MIPS_ASE_LOONGSON_EXT | MIPS_ASE_LOONGSON_EXT2);
> --
> 2.28.0
>