linux-kernel - Re: [PATCH 2/3] cpuidle/powernv: Change platform init to avoid reparsing dt

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Message-Id: <20180620045255.GB21984@in.ibm.com>
Date:   Wed, 20 Jun 2018 10:22:55 +0530
From:   Gautham R Shenoy <ego@...ux.vnet.ibm.com>
To:     Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-pm@...r.kernel.org, rjw@...ysocki.net,
        svaidy@...ux.vnet.ibm.com, ego@...ux.vnet.ibm.com,
        npiggin@...il.com, mpe@...erman.id.au
Subject: Re: [PATCH 2/3] cpuidle/powernv: Change platform init to avoid
 reparsing dt

Hi Akshay,


On Tue, Jun 19, 2018 at 10:34:27AM +0530, Akshay Adiga wrote:
> The required data is accessible from cpuidle_states structure and
> nr_cpu_idle_states. This patch makes changes to avoid reparsing and use
> data from these structures.
> 
> Signed-off-by: Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/platforms/powernv/idle.c | 37 ++++++++---------------------------
>  1 file changed, 8 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index 07be984..0a62611 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -624,8 +624,7 @@ int validate_psscr_val_mask(u64 *psscr_val, u64 *psscr_mask, u32 flags)
>   * @dt_idle_states: Number of idle state entries
>   * Returns 0 on success
>   */
> -static int __init pnv_power9_idle_init(struct device_node *np, u32 *flags,
> -					int dt_idle_states)
> +static int __init pnv_power9_idle_init(void)
>  {
>  	u64 max_residency_ns = 0;
>  	int i;
> @@ -644,7 +643,7 @@ static int __init pnv_power9_idle_init(struct device_node *np, u32 *flags,
>  	 * the shallowest (OPAL_PM_STOP_INST_FAST) loss-less stop state.
>  	 */
>  	pnv_first_deep_stop_state = MAX_STOP_STATE;
> -	for (i = 0; i < dt_idle_states; i++) {
> +	for (i = 0; i < nr_pnv_idle_states; i++) {
>  		int err;
>  		struct pnv_idle_states_t *state = &pnv_idle_states[i];
>  		u64 psscr_rl = state->pm_ctrl_reg_val & PSSCR_RL_MASK;

These above two hunks could be folded into the first patch.

> @@ -704,41 +703,21 @@ static int __init pnv_power9_idle_init(struct device_node *np, u32 *flags,
>   */
>  static void __init pnv_probe_idle_states(void)

Can we move the remaining content of this function into the calling
function pnv_init_idle_states() ? That way...

>  {
> -	struct device_node *np;
> -	int dt_idle_states;
> -	u32 *flags = NULL;
>  	int i;
> 
> -	np = of_find_node_by_path("/ibm,opal/power-mgt");
> -	if (!np) {
> -		pr_warn("opal: PowerMgmt Node not found\n");
> -		goto out;
> -	}
> -	dt_idle_states = of_property_count_u32_elems(np,
> -			"ibm,cpu-idle-state-flags");
> -	if (dt_idle_states < 0) {
> +	if (nr_pnv_idle_states < 0) {

... This reduntant check can be removed. Because nr_pnv_idle_states is initialized to
zero) and if there is an error in parsing the device tree we don't set
up this value. If there is no error, then nr_pnv_idle_states is a
positive value. 



>  		pr_warn("cpuidle-powernv: no idle states found in the DT\n");
> -		goto out;
> -	}
> -
> -	flags = kcalloc(dt_idle_states, sizeof(*flags),  GFP_KERNEL);
> -
> -	if (of_property_read_u32_array(np,
> -			"ibm,cpu-idle-state-flags", flags, dt_idle_states)) {
> -		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-flags in DT\n");
> -		goto out;
> +		return;
>  	}
> 
>  	if (cpu_has_feature(CPU_FTR_ARCH_300)) {
> -		if (pnv_power9_idle_init(np, flags, dt_idle_states))
> -			goto out;
> +		if (pnv_power9_idle_init())

There cannot any longer be a failure in pnv_power9_idle_init() after
the first patch, since we always return a 0. So  this if condition can be removed.

> +			return;
>  	}
> 
> -	for (i = 0; i < dt_idle_states; i++)
> -		supported_cpuidle_states |= flags[i];
> +	for (i = 0; i < nr_pnv_idle_states; i++)
> +		supported_cpuidle_states |= pnv_idle_states[i].flags;

Ideally we should be setting the supported_cpuidle_states flags after
all the validatations have been done, including the ones for stop-api
initialization.

> 
> -out:
> -	kfree(flags);
>  }
> 
>  /*
> -- 
> 2.5.5
>