linux-kernel - Re: [PATCH v2] MIPS: add support for buggy MT7621S core detection

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Message-ID: <alpine.DEB.2.21.2104071549560.65251@angie.orcam.me.uk>
Date:   Wed, 7 Apr 2021 15:52:38 +0200 (CEST)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>
cc:     linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        liwei391@...wei.com, nbd@....name,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        yangtiezhu@...ngson.cn
Subject: Re: [PATCH v2] MIPS: add support for buggy MT7621S core detection

On Mon, 5 Apr 2021, Ilya Lipnitskiy wrote:

> diff --git a/arch/mips/include/asm/mips-cps.h b/arch/mips/include/asm/mips-cps.h
> index fd43d876892e..9f495ffef2b7 100644
> --- a/arch/mips/include/asm/mips-cps.h
> +++ b/arch/mips/include/asm/mips-cps.h
> @@ -165,11 +167,29 @@ static inline uint64_t mips_cps_cluster_config(unsigned int cluster)
>   */
>  static inline unsigned int mips_cps_numcores(unsigned int cluster)
>  {
> +	struct cpulaunch *launch;
> +	unsigned int ncores;
> +
>  	if (!mips_cm_present())
>  		return 0;
>  
>  	/* Add one before masking to handle 0xff indicating no cores */
> -	return (mips_cps_cluster_config(cluster) + 1) & CM_GCR_CONFIG_PCORES;
> +	ncores = (mips_cps_cluster_config(cluster) + 1) & CM_GCR_CONFIG_PCORES;
> +
> +	if (IS_ENABLED(CONFIG_SOC_MT7621)) {
> +		/*
> +		 * Ralink MT7621S SoC is single core, but the GCR_CONFIG method
> +		 * always reports 2 cores. Check the second core's LAUNCH_FREADY
> +		 * flag to detect if the second core is missing. This method
> +		 * only works before the core has been started.
> +		 */
> +		launch = (struct cpulaunch *)CKSEG0ADDR(CPULAUNCH);
> +		launch += 2; /* MT7621 has 2 VPEs per core */
> +		if (!(launch->flags & LAUNCH_FREADY))
> +			ncores = 1;
> +	}
> +
> +	return ncores;
>  }
>  
>  /**

 Much better to me, but please move the declaration of `launch' into the 
conditional block, which is the only place that uses it.

  Maciej