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SubjectRe: [PATCH 5/7] drivers: firmware: psci: Simplify state node parsing
On Thu, Feb 28, 2019 at 02:59:17PM +0100, Ulf Hansson wrote:
> Instead of iterating through all the state nodes in DT, to find out how
> many states that needs to be allocated, let's use the number already known
> by the cpuidle driver. In this way we can drop the iteration altogether.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
> drivers/firmware/psci/psci.c | 25 ++++++++++++-------------
> 1 file changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index d50b46a0528f..cbfc936d251c 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -290,26 +290,20 @@ static int psci_dt_parse_state_node(struct device_node *np, u32 *state)
> static int psci_dt_cpu_init_idle(struct cpuidle_driver *drv,
> struct device_node *cpu_node, int cpu)
> {
> - int i, ret = 0, count = 0;
> + int i, ret = 0, num_state_nodes = drv->state_count - 1;
> u32 *psci_states;
> struct device_node *state_node;
>
> - /* Count idle states */
> - while ((state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
> - count))) {
> - count++;
> - of_node_put(state_node);
> - }
> -

To be honest, I'd rather not tighten the coupling with the cpuidle
driver here. For example, I'm not that happy with the PSCI backend
having to know the driver has a specific WFI state.

IIUC we could get rid of the explicit counting with something like:

count = of_parse_phandle_with_args(cpu_node, "cpu-idle-states", NULL);

... but I'm not sure that the overall change is a simplification.

Does this change make it easier to plumb in something in future?

Thanks,
Mark.

> - if (!count)
> - return -ENODEV;
> -
> - psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
> + psci_states = kcalloc(num_state_nodes, sizeof(*psci_states),
> + GFP_KERNEL);
> if (!psci_states)
> return -ENOMEM;
>
> - for (i = 0; i < count; i++) {
> + for (i = 0; i < num_state_nodes; i++) {
> state_node = of_parse_phandle(cpu_node, "cpu-idle-states", i);
> + if (!state_node)
> + break;
> +
> ret = psci_dt_parse_state_node(state_node, &psci_states[i]);
> of_node_put(state_node);
>
> @@ -319,6 +313,11 @@ static int psci_dt_cpu_init_idle(struct cpuidle_driver *drv,
> pr_debug("psci-power-state %#x index %d\n", psci_states[i], i);
> }
>
> + if (i != num_state_nodes) {
> + ret = -ENODEV;
> + goto free_mem;
> + }
> +
> /* Idle states parsed correctly, initialize per-cpu pointer */
> per_cpu(psci_power_state, cpu) = psci_states;
> return 0;
> --
> 2.17.1
>

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