[Nouveau] [RFC PATCH 06/29] clk: Make pstate a pointer to nvkm_pstate

Pierre Moreau
2017-10-08T11:47:33Z

The patch seems fine but I found it super confusing that sometimes `pstate` is
a pointer (for example `clk->pstate`), sometimes it is an int (for example
`args->v0.pstate`).

On 2017-09-15 — 17:11, Karol Herbst wrote:
> We will access the current cstate at least every second and this saves us
> some CPU cycles looking them up every second.
>
> v2: Rewording commit message.
>
> Signed-off-by: Karol Herbst <karolherbst at gmail.com>
> Reviewed-by: Martin Peres <martin.peres at free.fr>
> ---
>  drm/nouveau/include/nvkm/subdev/clk.h |  4 +++-
>  drm/nouveau/nvkm/engine/device/ctrl.c |  5 ++++-
>  drm/nouveau/nvkm/subdev/clk/base.c    | 17 ++++++++++++-----
>  drm/nouveau/nvkm/subdev/pmu/gk20a.c   | 18 +++++++-----------
>  4 files changed, 26 insertions(+), 18 deletions(-)
>
> diff --git a/drm/nouveau/include/nvkm/subdev/clk.h
b/drm/nouveau/include/nvkm/subdev/clk.h
> index 1340f5b8..ec537e08 100644
> --- a/drm/nouveau/include/nvkm/subdev/clk.h
> +++ b/drm/nouveau/include/nvkm/subdev/clk.h
> @@ -10,6 +10,8 @@ struct nvkm_pll_vals;
>  #define NVKM_CLK_CSTATE_BASE    -2 /* pstate base */
>  #define NVKM_CLK_CSTATE_HIGHEST -3 /* highest possible */
>
> +#define NVKM_CLK_PSTATE_DEFAULT -1
> +
>  enum nv_clk_src {
>  	nv_clk_src_crystal,
>  	nv_clk_src_href,
> @@ -95,7 +97,7 @@ struct nvkm_clk {
>
>  	struct nvkm_notify pwrsrc_ntfy;
>  	int pwrsrc;
> -	int pstate; /* current */
> +	struct nvkm_pstate *pstate; /* current */
>  	int ustate_ac; /* user-requested (-1 disabled, -2 perfmon) */
>  	int ustate_dc; /* user-requested (-1 disabled, -2 perfmon) */
>  	int astate; /* perfmon adjustment (base) */
> diff --git a/drm/nouveau/nvkm/engine/device/ctrl.c
b/drm/nouveau/nvkm/engine/device/ctrl.c
> index b0ece71a..da70626c 100644
> --- a/drm/nouveau/nvkm/engine/device/ctrl.c
> +++ b/drm/nouveau/nvkm/engine/device/ctrl.c
> @@ -52,7 +52,10 @@ nvkm_control_mthd_pstate_info(struct nvkm_control *ctrl,
void *data, u32 size)
>  		args->v0.ustate_ac = clk->ustate_ac;
>  		args->v0.ustate_dc = clk->ustate_dc;
>  		args->v0.pwrsrc = clk->pwrsrc;
> -		args->v0.pstate = clk->pstate;
> +		if (clk->pstate)
> +			args->v0.pstate = clk->pstate->pstate;
> +		else
> +			args->v0.pstate = NVKM_CLK_PSTATE_DEFAULT;
>  	} else {
>  		args->v0.count = 0;
>  		args->v0.ustate_ac = NVIF_CONTROL_PSTATE_INFO_V0_USTATE_DISABLE;
> diff --git a/drm/nouveau/nvkm/subdev/clk/base.c
b/drm/nouveau/nvkm/subdev/clk/base.c
> index 07d530ed..0d4d9fdf 100644
> --- a/drm/nouveau/nvkm/subdev/clk/base.c
> +++ b/drm/nouveau/nvkm/subdev/clk/base.c
> @@ -271,13 +271,16 @@ nvkm_pstate_prog(struct nvkm_clk *clk, int pstatei)
>  	struct nvkm_pstate *pstate;
>  	int ret, idx = 0;
>
> +	if (pstatei == NVKM_CLK_PSTATE_DEFAULT)
> +		return 0;
> +
>  	list_for_each_entry(pstate, &clk->states, head) {
>  		if (idx++ == pstatei)
>  			break;
>  	}
>
>  	nvkm_debug(subdev, "setting performance state %d\n", pstatei);
> -	clk->pstate = pstatei;
> +	clk->pstate = pstate;
>
>  	nvkm_pcie_set_link(pci, pstate->pcie_speed, pstate->pcie_width);
>
> @@ -306,8 +309,12 @@ nvkm_clk_update_work(struct work_struct *work)
>  		return;
>  	clk->pwrsrc = power_supply_is_system_supplied();
>
> +	if (clk->pstate)
> +		pstate = clk->pstate->pstate;
> +	else
> +		pstate = NVKM_CLK_PSTATE_DEFAULT;
>  	nvkm_trace(subdev, "P %d PWR %d U(AC) %d U(DC) %d A %d T
%d°C\n",
> -		   clk->pstate, clk->pwrsrc, clk->ustate_ac, clk->ustate_dc,
> +		   pstate, clk->pwrsrc, clk->ustate_ac, clk->ustate_dc,
>  		   clk->astate, clk->temp);
>
>  	pstate = clk->pwrsrc ? clk->ustate_ac : clk->ustate_dc;

In the if-statement following the previous line, the -1 could be replaced by
NVKM_CLK_PSTATE_DEFAULT.

> @@ -315,11 +322,11 @@ nvkm_clk_update_work(struct work_struct *work)
>  		pstate = (pstate < 0) ? clk->astate : pstate;

Can `pstate` have negative values other than -1?

>  		pstate = min(pstate, clk->state_nr - 1);
>  	} else {
> -		pstate = clk->pstate = -1;
> +		pstate = NVKM_CLK_PSTATE_DEFAULT;

Shouldn’t you also reset `clk->pstate` to NULL? Or maybe it is
`nvkm_pstate_prog()` which should do it if
`pstatei == NVKM_CLK_PSTATE_DEFAULT`.

>  	}
>
>  	nvkm_trace(subdev, "-> %d\n", pstate);
> -	if (pstate != clk->pstate) {
> +	if (!clk->pstate || pstate != clk->pstate->pstate) {
>  		int ret = nvkm_pstate_prog(clk, pstate);
>  		if (ret) {
>  			nvkm_error(subdev, "error setting pstate %d: %d\n",
> @@ -610,7 +617,7 @@ nvkm_clk_init(struct nvkm_subdev *subdev)
>  		return clk->func->init(clk);
>
>  	clk->astate = clk->state_nr - 1;
> -	clk->pstate = -1;
> +	clk->pstate = NULL;
>  	clk->temp = 90; /* reasonable default value */
>  	nvkm_clk_update(clk, true);
>  	return 0;
> diff --git a/drm/nouveau/nvkm/subdev/pmu/gk20a.c
b/drm/nouveau/nvkm/subdev/pmu/gk20a.c
> index 05e81855..de579726 100644
> --- a/drm/nouveau/nvkm/subdev/pmu/gk20a.c
> +++ b/drm/nouveau/nvkm/subdev/pmu/gk20a.c
> @@ -55,24 +55,22 @@ gk20a_pmu_dvfs_target(struct gk20a_pmu *pmu, int
*state)
>  	return nvkm_clk_astate(clk, *state, 0, false);
>  }
>
> -static void
> -gk20a_pmu_dvfs_get_cur_state(struct gk20a_pmu *pmu, int *state)
> -{
> -	struct nvkm_clk *clk = pmu->base.subdev.device->clk;
> -
> -	*state = clk->pstate;
> -}
> -
>  static int
>  gk20a_pmu_dvfs_get_target_state(struct gk20a_pmu *pmu,
>  				int *state, int load)
>  {
>  	struct gk20a_pmu_dvfs_data *data = pmu->data;
>  	struct nvkm_clk *clk = pmu->base.subdev.device->clk;
> +	struct nvkm_pstate *pstate = clk->pstate;
>  	int cur_level, level;
>
> +	if (!pstate) {
> +		*state = 0;
> +		return 1;
> +	}
> +
>  	/* For GK20A, the performance level is directly mapped to pstate */
> -	level = cur_level = clk->pstate;
> +	level = cur_level = clk->pstate->pstate;
>
>  	if (load > data->p_load_max) {
>  		level = min(clk->state_nr - 1, level + (clk->state_nr / 3));
> @@ -142,8 +140,6 @@ gk20a_pmu_dvfs_work(struct nvkm_alarm *alarm)
>  	nvkm_trace(subdev, "utilization = %d %%, avg_load = %d %%\n",
>  		   utilization, data->avg_load);
>
> -	gk20a_pmu_dvfs_get_cur_state(pmu, &state);
> -
>  	if (gk20a_pmu_dvfs_get_target_state(pmu, &state, data->avg_load))
{
>  		nvkm_trace(subdev, "set new state to %d\n", state);
>  		gk20a_pmu_dvfs_target(pmu, &state);
> --
> 2.14.1
>
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