linux-kernel - Re: [RESEND PATCH v2 3/3] powerpc/powernv: Parse device tree, population of SPR support

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Date:   Sun, 12 Jan 2020 23:55:33 -0800
From:   Ram Pai <linuxram@...ibm.com>
To:     Pratik Rajesh Sampat <psampat@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
        mpe@...erman.id.au, svaidy@...ux.ibm.com, ego@...ux.vnet.ibm.com,
        pratik.sampat@...ibm.com, pratik.r.sampat@...il.com
Subject: Re: [RESEND PATCH v2 3/3] powerpc/powernv: Parse device tree,
 population of SPR support

On Mon, Jan 13, 2020 at 09:15:09AM +0530, Pratik Rajesh Sampat wrote:
> Parse the device tree for nodes self-save, self-restore and populate
> support for the preferred SPRs based what was advertised by the device
> tree.
> 
> Signed-off-by: Pratik Rajesh Sampat <psampat@...ux.ibm.com>
> ---
>  arch/powerpc/platforms/powernv/idle.c | 104 ++++++++++++++++++++++++++
>  1 file changed, 104 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index d67d4d0b169b..e910ff40b7e6 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -1429,6 +1429,107 @@ static void __init pnv_probe_idle_states(void)
>  		supported_cpuidle_states |= pnv_idle_states[i].flags;
>  }
> 
> +/*
> + * Extracts and populates the self save or restore capabilities
> + * passed from the device tree node
> + */
> +static int extract_save_restore_state_dt(struct device_node *np, int type)
> +{
> +	int nr_sprns = 0, i, bitmask_index;
> +	int rc = 0;
> +	u64 *temp_u64;
> +	const char *state_prop;
> +	u64 bit_pos;
> +
> +	state_prop = of_get_property(np, "status", NULL);
> +	if (!state_prop) {
> +		pr_warn("opal: failed to find the active value for self save/restore node");
> +		return -EINVAL;
> +	}
> +	if (strncmp(state_prop, "disabled", 8) == 0) {
> +		/*
> +		 * if the feature is not active, strip the preferred_sprs from
> +		 * that capability.
> +		 */
> +		if (type == SELF_RESTORE_TYPE) {
> +			for (i = 0; i < nr_preferred_sprs; i++) {
> +				preferred_sprs[i].supported_mode &=
> +					~SELF_RESTORE_STRICT;
> +			}
> +		} else {
> +			for (i = 0; i < nr_preferred_sprs; i++) {
> +				preferred_sprs[i].supported_mode &=
> +					~SELF_SAVE_STRICT;
> +			}
> +		}
> +		return 0;
> +	}
> +	nr_sprns = of_property_count_u64_elems(np, "sprn-bitmask");
> +	if (nr_sprns <= 0)
> +		return rc;
> +	temp_u64 = kcalloc(nr_sprns, sizeof(u64), GFP_KERNEL);
> +	if (of_property_read_u64_array(np, "sprn-bitmask",
> +				       temp_u64, nr_sprns)) {
> +		pr_warn("cpuidle-powernv: failed to find registers in DT\n");
> +		kfree(temp_u64);
> +		return -EINVAL;
> +	}
> +	/*
> +	 * Populate acknowledgment of support for the sprs in the global vector
> +	 * gotten by the registers supplied by the firmware.
> +	 * The registers are in a bitmask, bit index within
> +	 * that specifies the SPR
> +	 */
> +	for (i = 0; i < nr_preferred_sprs; i++) {
> +		bitmask_index = preferred_sprs[i].spr / 64;
> +		bit_pos = preferred_sprs[i].spr % 64;
> +		if ((temp_u64[bitmask_index] & (1UL << bit_pos)) == 0) {
> +			if (type == SELF_RESTORE_TYPE)
> +				preferred_sprs[i].supported_mode &=
> +					~SELF_RESTORE_STRICT;
> +			else
> +				preferred_sprs[i].supported_mode &=
> +					~SELF_SAVE_STRICT;
> +			continue;
> +		}
> +		if (type == SELF_RESTORE_TYPE) {
> +			preferred_sprs[i].supported_mode |=
> +				SELF_RESTORE_STRICT;
> +		} else {
> +			preferred_sprs[i].supported_mode |=
> +				SELF_SAVE_STRICT;
> +		}
> +	}
> +
> +	kfree(temp_u64);
> +	return rc;
> +}
> +
> +static int pnv_parse_deepstate_dt(void)
> +{
> +	struct device_node *np, *np1;
> +	int rc = 0;
> +
> +	/* Self restore register population */
> +	np = of_find_node_by_path("/ibm,opal/power-mgt/self-restore");
> +	if (!np) {
> +		pr_warn("opal: self restore Node not found");
> +	} else {
> +		rc = extract_save_restore_state_dt(np, SELF_RESTORE_TYPE);
> +		if (rc != 0)
> +			return rc;
> +	}
> +	/* Self save register population */
> +	np1 = of_find_node_by_path("/ibm,opal/power-mgt/self-save");

'np' can be reused?  'np1' is not needed.


Otherwise looks good.

Reviewed-by: Ram Pai <linuxram@...ibm.com>

RP