linux-kernel - Re: [PATCH v4 2/2] riscv: Add support to determine no. of L2 cache way enabled

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Date:   Fri, 07 Feb 2020 10:24:19 -0800 (PST)
From:   Palmer Dabbelt <palmerdabbelt@...gle.com>
To:     yash.shah@...ive.com
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        allison@...utok.net, alexios.zavras@...el.com,
        Greg KH <gregkh@...uxfoundation.org>, tglx@...utronix.de,
        bp@...e.de, anup@...infault.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, sachin.ghadi@...ive.com,
        yash.shah@...ive.com
Subject:     Re: [PATCH v4 2/2] riscv: Add support to determine no. of L2 cache way enabled

On Thu, 16 Jan 2020 23:43:38 PST (-0800), yash.shah@...ive.com wrote:
> In order to determine the number of L2 cache ways enabled at runtime,
> implement a private attribute ("number_of_ways_enabled"). Reading this
> attribute returns the number of enabled L2 cache ways at runtime.
>
> Using riscv_set_cacheinfo_ops() hook a custom function, that returns
> this private attribute, to the generic ops structure which is used by
> cache_get_priv_group() in cacheinfo framework.
>
> Signed-off-by: Yash Shah <yash.shah@...ive.com>
> Reviewed-by: Anup Patel <anup@...infault.org>
> ---
>  drivers/soc/sifive/sifive_l2_cache.c | 38 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/drivers/soc/sifive/sifive_l2_cache.c b/drivers/soc/sifive/sifive_l2_cache.c
> index a506939..3fb6404 100644
> --- a/drivers/soc/sifive/sifive_l2_cache.c
> +++ b/drivers/soc/sifive/sifive_l2_cache.c
> @@ -9,6 +9,8 @@
>  #include <linux/interrupt.h>
>  #include <linux/of_irq.h>
>  #include <linux/of_address.h>
> +#include <linux/device.h>
> +#include <asm/cacheinfo.h>
>  #include <soc/sifive/sifive_l2_cache.h>
>
>  #define SIFIVE_L2_DIRECCFIX_LOW 0x100
> @@ -31,6 +33,7 @@
>
>  static void __iomem *l2_base;
>  static int g_irq[SIFIVE_L2_MAX_ECCINTR];
> +static struct riscv_cacheinfo_ops l2_cache_ops;
>
>  enum {
>  	DIR_CORR = 0,
> @@ -107,6 +110,38 @@ int unregister_sifive_l2_error_notifier(struct notifier_block *nb)
>  }
>  EXPORT_SYMBOL_GPL(unregister_sifive_l2_error_notifier);
>
> +static int l2_largest_wayenabled(void)
> +{
> +	return readl(l2_base + SIFIVE_L2_WAYENABLE);
> +}

WayEnable is 8 bits.

> +
> +static ssize_t number_of_ways_enabled_show(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf)
> +{
> +	return sprintf(buf, "%u\n", l2_largest_wayenabled());
> +}
> +
> +static DEVICE_ATTR_RO(number_of_ways_enabled);
> +
> +static struct attribute *priv_attrs[] = {
> +	&dev_attr_number_of_ways_enabled.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group priv_attr_group = {
> +	.attrs = priv_attrs,
> +};
> +
> +const struct attribute_group *l2_get_priv_group(struct cacheinfo *this_leaf)
> +{
> +	/* We want to use private group for L2 cache only */
> +	if (this_leaf->level == 2)
> +		return &priv_attr_group;
> +	else
> +		return NULL;
> +}
> +
>  static irqreturn_t l2_int_handler(int irq, void *device)
>  {
>  	unsigned int add_h, add_l;
> @@ -170,6 +205,9 @@ static int __init sifive_l2_init(void)
>
>  	l2_config_read();
>
> +	l2_cache_ops.get_priv_group = l2_get_priv_group;
> +	riscv_set_cacheinfo_ops(&l2_cache_ops);
> +
>  #ifdef CONFIG_DEBUG_FS
>  	setup_sifive_debug();
>  #endif