linux-kernel - Re: [PATCH v2 2/3] cacheinfo: Check cache properties are present in DT

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Message-ID: <20230412-cone-mousiness-23326e149592@wendy>
Date:   Wed, 12 Apr 2023 08:55:34 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Pierre Gondois <pierre.gondois@....com>
CC:     <linux-kernel@...r.kernel.org>, Radu Rendec <rrendec@...hat.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v2 2/3] cacheinfo: Check cache properties are present in
 DT

Hey Pierre!

On Wed, Apr 12, 2023 at 09:18:05AM +0200, Pierre Gondois wrote:
> If a Device Tree (DT) is used, the presence of cache properties is
> assumed. Not finding any is not considered. For arm64 platforms,
> cache information can be fetched from the clidr_el1 register.
> Checking whether cache information is available in the DT
> allows to switch to using clidr_el1.
> 
> init_of_cache_level()
> \-of_count_cache_leaves()
> will assume there a 2 cache leaves (L1 data/instruction caches), which
> can be different from clidr_el1 information.
> 
> cache_setup_of_node() tries to read cache properties in the DT.
> If there are none, this is considered a success. Knowing no
> information was available would allow to switch to using clidr_el1.

Hmm, w/ this series I am still seeing a:
[    0.306736] Early cacheinfo failed, ret = -22

Not finding any cacheinfo is totally valid, right?

A basic RISC-V QEMU setup is sufficient to reproduce, for instance:
| $(qemu) \
| 	-m 2G -smp 5 \
| 	-M virt -nographic \
| 	-kernel $(vmlinux_bin)

Cheers,
Conor.

> Fixes: de0df442ee49 ("cacheinfo: Check 'cache-unified' property to count cache leaves")
> Reported-by: Alexandre Ghiti <alexghiti@...osinc.com>
> Link: https://lore.kernel.org/all/20230404-hatred-swimmer-6fecdf33b57a@spud/
> Signed-off-by: Pierre Gondois <pierre.gondois@....com>
> ---
>  drivers/base/cacheinfo.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index e7ad6aba5f97..6749dc6ebf50 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -78,6 +78,9 @@ bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y)
>  }
>  
>  #ifdef CONFIG_OF
> +
> +static bool of_check_cache_nodes(struct device_node *np);
> +
>  /* OF properties to query for a given cache type */
>  struct cache_type_info {
>  	const char *size_prop;
> @@ -205,6 +208,11 @@ static int cache_setup_of_node(unsigned int cpu)
>  		return -ENOENT;
>  	}
>  
> +	if (!of_check_cache_nodes(np)) {
> +		of_node_put(np);
> +		return -ENOENT;
> +	}
> +
>  	prev = np;
>  
>  	while (index < cache_leaves(cpu)) {
> @@ -229,6 +237,25 @@ static int cache_setup_of_node(unsigned int cpu)
>  	return 0;
>  }
>  
> +static bool of_check_cache_nodes(struct device_node *np)
> +{
> +	struct device_node *next;
> +
> +	if (of_property_present(np, "cache-size")   ||
> +	    of_property_present(np, "i-cache-size") ||
> +	    of_property_present(np, "d-cache-size") ||
> +	    of_property_present(np, "cache-unified"))
> +		return true;
> +
> +	next = of_find_next_cache_node(np);
> +	if (next) {
> +		of_node_put(next);
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
>  static int of_count_cache_leaves(struct device_node *np)
>  {
>  	unsigned int leaves = 0;
> @@ -260,6 +287,9 @@ int init_of_cache_level(unsigned int cpu)
>  	struct device_node *prev = NULL;
>  	unsigned int levels = 0, leaves, level;
>  
> +	if (!of_check_cache_nodes(np))
> +		goto err_out;
> +
>  	leaves = of_count_cache_leaves(np);
>  	if (leaves > 0)
>  		levels = 1;
> -- 
> 2.25.1
> 

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