1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  PCM DRM helpers
4  */
5 #include <linux/export.h>
6 #include <drm/drm_edid.h>
7 #include <sound/pcm.h>
8 #include <sound/pcm_drm_eld.h>
9 
10 static const unsigned int eld_rates[] = {
11 	32000,
12 	44100,
13 	48000,
14 	88200,
15 	96000,
16 	176400,
17 	192000,
18 };
19 
sad_max_channels(const u8 * sad)20 static unsigned int sad_max_channels(const u8 *sad)
21 {
22 	return 1 + (sad[0] & 7);
23 }
24 
eld_limit_rates(struct snd_pcm_hw_params * params,struct snd_pcm_hw_rule * rule)25 static int eld_limit_rates(struct snd_pcm_hw_params *params,
26 			   struct snd_pcm_hw_rule *rule)
27 {
28 	struct snd_interval *r = hw_param_interval(params, rule->var);
29 	const struct snd_interval *c;
30 	unsigned int rate_mask = 7, i;
31 	const u8 *sad, *eld = rule->private;
32 
33 	sad = drm_eld_sad(eld);
34 	if (sad) {
35 		c = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_CHANNELS);
36 
37 		for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
38 			unsigned max_channels = sad_max_channels(sad);
39 
40 			/*
41 			 * Exclude SADs which do not include the
42 			 * requested number of channels.
43 			 */
44 			if (c->min <= max_channels)
45 				rate_mask |= sad[1];
46 		}
47 	}
48 
49 	return snd_interval_list(r, ARRAY_SIZE(eld_rates), eld_rates,
50 				 rate_mask);
51 }
52 
eld_limit_channels(struct snd_pcm_hw_params * params,struct snd_pcm_hw_rule * rule)53 static int eld_limit_channels(struct snd_pcm_hw_params *params,
54 			      struct snd_pcm_hw_rule *rule)
55 {
56 	struct snd_interval *c = hw_param_interval(params, rule->var);
57 	const struct snd_interval *r;
58 	struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
59 	unsigned int i;
60 	const u8 *sad, *eld = rule->private;
61 
62 	sad = drm_eld_sad(eld);
63 	if (sad) {
64 		unsigned int rate_mask = 0;
65 
66 		/* Convert the rate interval to a mask */
67 		r = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
68 		for (i = 0; i < ARRAY_SIZE(eld_rates); i++)
69 			if (r->min <= eld_rates[i] && r->max >= eld_rates[i])
70 				rate_mask |= BIT(i);
71 
72 		for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3)
73 			if (rate_mask & sad[1])
74 				t.max = max(t.max, sad_max_channels(sad));
75 	}
76 
77 	return snd_interval_refine(c, &t);
78 }
79 
snd_pcm_hw_constraint_eld(struct snd_pcm_runtime * runtime,void * eld)80 int snd_pcm_hw_constraint_eld(struct snd_pcm_runtime *runtime, void *eld)
81 {
82 	int ret;
83 
84 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
85 				  eld_limit_rates, eld,
86 				  SNDRV_PCM_HW_PARAM_CHANNELS, -1);
87 	if (ret < 0)
88 		return ret;
89 
90 	ret = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
91 				  eld_limit_channels, eld,
92 				  SNDRV_PCM_HW_PARAM_RATE, -1);
93 
94 	return ret;
95 }
96 EXPORT_SYMBOL_GPL(snd_pcm_hw_constraint_eld);
97