Re: [PATCH i-g-t 1/2] tests/intel: Add kms_hdmi_audio_bw test

["Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com>]

On 8/31/2026 2:25 PM, Borah, Chaitanya Kumar wrote:
> 
> 
> On 8/19/2026 1:08 PM, Swati Sharma wrote:
>> Add a new IGT test to validate HDMI TMDS audio bandwidth constraints
>> under constrained horizontal blanking intervals.
>>
>> The test injects EDIDs declaring all 7 CEA sample rates (32kHz-192kHz)
>> and observes which rates the driver exposes via ELD (EDID-Like Data)
>> under varying BPC and channel configurations.
>>
>> Subtests:
>> - audio-bw-supported: Baseline with hblank=160 where audio bandwidth
>>    is sufficient for all configurations.
>> - audio-bw-pruned: Constrained hblank=80 (CVT RB2) where the driver
>>    must prune unsustainable sample rates or disable audio entirely.
>> - suspend-s3/s4-audio-recovery: Verify audio state and sample rates
>>    are preserved across system suspend/resume.
>> - runtime-suspend-audio-recovery: Verify audio state is preserved
>>    across DPMS off/on cycles.
>>
>> The test uses the HDMI TMDS bandwidth formula from the spec:
>>    pkts_avail = FLOOR((CEIL(hblank * bpc/8) - overhead) / 32)
>>    pkts_reqd  = CEIL(R_AP * T_line)
>> where overhead=74 (HDCP 1.4 rekey always reserved by the driver).
>>
>> Assertions verify:
>> - Audio is active when bandwidth is available (pkts_avail > 0)
>> - Audio is inactive when bandwidth is exhausted (pkts_avail == 0)
>> - No sample rate requiring more packets than available appears in ELD
>>
>> Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
>> Assisted-by: GitHub Copilot:Claude Opus 4.6
>> ---
>>   tests/intel/kms_hdmi_audio_bw.c | 626 ++++++++++++++++++++++++++++++++
>>   tests/meson.build               |   1 +
>>   2 files changed, 627 insertions(+)
>>   create mode 100644 tests/intel/kms_hdmi_audio_bw.c
>>
>> diff --git a/tests/intel/kms_hdmi_audio_bw.c b/tests/intel/ 
>> kms_hdmi_audio_bw.c
>> new file mode 100644
>> index 000000000..4b6f0d001
>> --- /dev/null
>> +++ b/tests/intel/kms_hdmi_audio_bw.c
>> @@ -0,0 +1,626 @@
>> +// SPDX-License-Identifier: MIT
>> +/*
>> + * Copyright © 2026 Intel Corporation
>> + */
>> +
>> +/**
>> + * TEST: kms hdmi audio bw
>> + * Category: Display
>> + * Description: Validate HDMI TMDS audio bandwidth constraints by 
>> injecting
>> + *              EDIDs with all sample rates declared and observing 
>> which rates
>> + *              the driver exposes (via ELD) under varying BPC / 
>> channel /
>> + *              hblank configurations.
>> + * Driver requirement: i915, xe
>> + * Mega feature: Display Audio
>> + */
>> +
>> +#include "config.h"
>> +
>> +#include <math.h>
>> +#include <string.h>
>> +
>> +#include "igt.h"
>> +#include "igt_edid.h"
>> +#include "igt_eld.h"
>> +#include "igt_aux.h"
>> +#include "xe/xe_query.h"
> 
> What is this used for?
> 
>> +
>> +/**
>> + * SUBTEST: audio-bw-supported
>> + * Description: Baseline test with hblank=160 where audio bandwidth is
>> + *              sufficient for all BPC and channel combinations. 
>> Verifies
>> + *              that no sample rates are pruned.
>> + *
>> + * SUBTEST: audio-bw-pruned
>> + * Description: Constrained test with hblank=80 (CVT RB2) where audio
>> + *              bandwidth is limited. Logs which sample rates are pruned
>> + *              per BPC and channel combination.
>> + *
>> + * SUBTEST: suspend-%s-audio-recovery
>> + * Description: Validate audio state restoration after %arg[1] with
>> + *              constrained hblank=80 and 12bpc.
>> + *
>> + * arg[1]:
>> + *
>> + * @s3:  S3 (suspend to RAM)
>> + * @s4:  S4 (hibernate)
>> + *
>> + * SUBTEST: runtime-suspend-audio-recovery
>> + * Description: Validate audio state restoration after runtime 
>> suspend/resume
>> + *              with constrained hblank=80 and 12bpc.
>> + */
>> +
>> +IGT_TEST_DESCRIPTION("Validate HDMI TMDS audio bandwidth constraints. "
>> +              "EDIDs declare all sample rates (32k-192k); the test "
>> +              "observes which rates survive in the ELD under "
>> +              "constrained hblank timings.");
>> +
>> +typedef struct {
>> +    int drm_fd;
>> +    igt_display_t display;
>> +    igt_output_t *output;
>> +    igt_crtc_t *crtc;
>> +    struct igt_fb fb;
>> +} data_t;
>> +
>> +/* All sample rates declared in the EDID SAD */
>> +#define ALL_SAMPLE_RATES (CEA_SAD_SAMPLING_RATE_32KHZ | \
>> +              CEA_SAD_SAMPLING_RATE_44KHZ | \
>> +              CEA_SAD_SAMPLING_RATE_48KHZ | \
>> +              CEA_SAD_SAMPLING_RATE_88KHZ | \
>> +              CEA_SAD_SAMPLING_RATE_96KHZ | \
>> +              CEA_SAD_SAMPLING_RATE_176KHZ | \
>> +              CEA_SAD_SAMPLING_RATE_192KHZ)
>> +
>> +struct rate_info {
>> +    unsigned int flag;
>> +    const char *name;
>> +    int freq_hz;
>> +};
>> +
>> +static const struct rate_info rate_table[] = {
>> +    { CEA_SAD_SAMPLING_RATE_32KHZ,  "32k",   32000 },
>> +    { CEA_SAD_SAMPLING_RATE_44KHZ,  "44.1k", 44100 },
>> +    { CEA_SAD_SAMPLING_RATE_48KHZ,  "48k",   48000 },
>> +    { CEA_SAD_SAMPLING_RATE_88KHZ,  "88k",   88200 },

I missed this, lets keep the naming consistent "88.2k"

>> +    { CEA_SAD_SAMPLING_RATE_96KHZ,  "96k",   96000 },
>> +    { CEA_SAD_SAMPLING_RATE_176KHZ, "176k",  176400 },

"176.4k"

Also see

https://lore.kernel.org/igt-dev/20260901113313.627816-1-chaitanya.kumar.borah@intel.com/T/#u

>> +    { CEA_SAD_SAMPLING_RATE_192KHZ, "192k",  192000 },
>> +};
>> +
>> +#define ACR_RATE_MAX        1500
>> +#define TOLERANCE_AUDIOCLK_PPM    1000
>> +#define TOLERANCE_PIXELCLK    0.005
>> +#define HBLANK_OVERHEAD_STD    30
>> +#define HBLANK_OVERHEAD_HDCP14    74
>> +#define DI_PACKET_SIZE        32
>> +
>> +static void rates_to_str(unsigned int rates, char *buf, size_t len)
>> +{
>> +    int pos = 0;
>> +
>> +    buf[0] = '\0';
>> +    for (int i = 0; i < ARRAY_SIZE(rate_table); i++) {
>> +        if (!(rates & rate_table[i].flag))
>> +            continue;
>> +        if (pos > 0)
>> +            pos += snprintf(buf + pos, len - pos, ",");
>> +        pos += snprintf(buf + pos, len - pos, "%s", rate_table[i].name);
>> +    }
>> +    if (pos == 0)
>> +        snprintf(buf, len, "none");
>> +}
>> +
>> +static const int bpc_values[] = { 8, 10, 12 };
>> +static const int channel_values[] = { 2, 8 };
>> +
>> +/*
>> + * 1920x1080@60Hz CVT RB2 — hblank=80 (constrained)
>> + * Available Packets/Line = FLOOR(((BPC/8)*80 - 74) / 32)
>> + *   8bpc=0, 10bpc=0, 12bpc=1
>> + */
>> +static const drmModeModeInfo mode_1080p_hblank80 = {
>> +    .clock = 133320,
>> +    .hdisplay = 1920,
>> +    .hsync_start = 1928,
>> +    .hsync_end = 1960,
>> +    .htotal = 2000,        /* hblank = 80 */
>> +    .vdisplay = 1080,
>> +    .vsync_start = 1097,
>> +    .vsync_end = 1105,
>> +    .vtotal = 1111,
>> +    .vrefresh = 60,
>> +    .flags = DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_NVSYNC,
>> +    .type = DRM_MODE_TYPE_DRIVER,
>> +    .name = "1920x1080",
>> +};
>> +
>> +/*
>> + * 1920x1080@60Hz with hblank=160 (relaxed baseline)
>> + * Enough hblank for audio at any BPC.
>> + */
>> +static const drmModeModeInfo mode_1080p_hblank160 = {
>> +    .clock = 148500,
>> +    .hdisplay = 1920,
>> +    .hsync_start = 1968,
>> +    .hsync_end = 2000,
>> +    .htotal = 2080,        /* hblank = 160 */
>> +    .vdisplay = 1080,
>> +    .vsync_start = 1097,
>> +    .vsync_end = 1105,
>> +    .vtotal = 1111,
>> +    .vrefresh = 60,
>> +    .flags = DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_NVSYNC,
>> +    .type = DRM_MODE_TYPE_DRIVER,
>> +    .name = "1920x1080",
>> +};
>> +
>> +static igt_output_t *find_hdmi_output(igt_display_t *display)
>> +{
>> +    igt_output_t *output;
>> +
>> +    for_each_connected_output(display, output) {
>> +        drmModeConnector *c = output->config.connector;
>> +
>> +        if (c->connector_type == DRM_MODE_CONNECTOR_HDMIA ||
>> +            c->connector_type == DRM_MODE_CONNECTOR_HDMIB)
>> +            return output;
>> +    }
>> +
>> +    return NULL;
>> +}
>> +
>> +static int hblank_of(const drmModeModeInfo *mode)
>> +{
>> +    return mode->htotal - mode->hdisplay;
>> +}
>> +
>> +/*
>> + * Driver always reserves HDCP 1.4 rekey overhead (74 clocks) even when
>> + * HDCP is not active: 30 (standard) + 44 (HDCP 1.4 rekey quiet period).
>> + * FIXME: once driver exposes HDCP state, use 30 for no HDCP, 74 for 
>> HDCP 1.4.
>> + */
>> +static int avail_pkts_per_line(int bpc, int hblank)
>> +{
>> +    int overhead = HBLANK_OVERHEAD_HDCP14;
>> +    int tb_blank = (bpc * hblank + 7) / 8; /* CEIL(hblank * bpc/8) */
>> +    int avail = (tb_blank - overhead) / DI_PACKET_SIZE;
>> +
>> +    return avail > 0 ? avail : 0;
>> +}
>> +
>> +/* Packets required per line for a given audio rate and channel 
>> layout */
>> +static int required_pkts_per_line(const drmModeModeInfo *mode, int 
>> freq_hz,
>> +                 int channels)
>> +{
>> +    double ap = (channels <= 2) ? 0.25 : 1.0;
>> +    double f_pixel_max = mode->clock * 1000.0 * (1 + 
>> TOLERANCE_PIXELCLK);
>> +    double t_line = mode->htotal / f_pixel_max;
>> +    double r_ap = ((freq_hz * ap) + (2 * ACR_RATE_MAX)) *
>> +              (1 + TOLERANCE_AUDIOCLK_PPM / 1e6);
>> +
>> +    double avg_pkts = r_ap * t_line;
>> +
>> +    return (int)avg_pkts + (avg_pkts > (int)avg_pkts ? 1 : 0);
>> +}
>> +
>> +/*
>> + * Build a CEA EDID declaring all 7 sample rates in the SAD.
>> + * Deep-color flags in HDMI VSDB match the requested bpc.
>> + */
>> +static const struct edid *
>> +build_edid(int bpc, int audio_channels)
>> +{
>> +    static unsigned char raw_edid[2 * EDID_BLOCK_SIZE];
>> +    struct edid *edid;
>> +    struct edid_ext *ext;
>> +    struct edid_cea *cea;
>> +    struct edid_cea_data_block *block;
>> +    struct cea_sad sad;
>> +    struct hdmi_vsdb hdmi;
> 
> nit: Let's call it vsdb.
> 
>> +    struct cea_speaker_alloc speakers;
>> +    size_t offset = 0;
>> +
>> +    memset(raw_edid, 0, sizeof(raw_edid));
>> +    edid = (struct edid *)raw_edid;
>> +    memcpy(edid, igt_kms_get_base_edid(), sizeof(struct edid));
>> +    edid->extensions_len = 1;
>> +
>> +    ext = &edid->extensions[0];
>> +    cea = &ext->data.cea;
>> +
>> +    if (audio_channels > 0) {
>> +        cea_sad_init_pcm(&sad,
>> +                 audio_channels,
>> +                 ALL_SAMPLE_RATES,
>> +                 CEA_SAD_SAMPLE_SIZE_16 |
>> +                 CEA_SAD_SAMPLE_SIZE_24);
>> +        block = (struct edid_cea_data_block *)&cea->data[offset];
>> +        offset += edid_cea_data_block_set_sad(block, &sad, 1);
>> +    }
>> +
>> +    memset(&hdmi, 0, sizeof(hdmi));
>> +    hdmi.src_phy_addr[0] = 0x10;
>> +    hdmi.src_phy_addr[1] = 0x00;
>> +    hdmi.flags1 = HDMI_VSDB_SUPPORTS_AI;
>> +    hdmi.max_tdms_clock = 340000000 / (5 * 1000000);
> 
> where do these number come from?
> 
>> +
>> +    switch (bpc) {
>> +    case 12:
>> +        hdmi.flags1 |= HDMI_VSDB_DC_36BIT;
>> +        /* fall through */
>> +    case 10:
>> +        hdmi.flags1 |= HDMI_VSDB_DC_30BIT;
>> +        /* fall through */
>> +    case 8:
>> +        break;
>> +    }
>> +
>> +    block = (struct edid_cea_data_block *)&cea->data[offset];
>> +    offset += edid_cea_data_block_set_hdmi_vsdb(block, &hdmi,
>> +                            sizeof(hdmi));
>> +
>> +    memset(&speakers, 0, sizeof(speakers));
>> +    speakers.speakers = CEA_SPEAKER_FRONT_LEFT_RIGHT;
>> +    if (audio_channels > 2)
>> +        speakers.speakers |= CEA_SPEAKER_FRONT_CENTER |
>> +                     CEA_SPEAKER_LFE |
>> +                     CEA_SPEAKER_REAR_LEFT_RIGHT;
> 
> Not really a problem for this test but we are adding 6 speakers for 
> anything with greater than 2 channels.
> 
> 
>> +    block = (struct edid_cea_data_block *)&cea->data[offset];
>> +    offset += edid_cea_data_block_set_speaker_alloc(block, &speakers);
>> +
>> +    edid_ext_set_cea(ext, offset, 0,
>> +             EDID_CEA_BASIC_AUDIO | EDID_CEA_UNDERSCAN |
>> +             EDID_CEA_YCBCR444 | EDID_CEA_YCBCR422);
>> +    edid_update_checksum(edid);
>> +
>> +    return edid;
>> +}
>> +
>> +static void force_edid_and_connector(data_t *data, const struct edid 
>> *edid)
>> +{
>> +    kmstest_force_edid(data->drm_fd, data->output->config.connector, 
>> edid);
>> +    igt_skip_on_f(!kmstest_force_connector(data->drm_fd,
>> +                           data->output->config.connector,
>> +                           FORCE_CONNECTOR_ON),
>> +              "Could not force HDMI connector on\n");
>> +}
>> +
>> +static void cleanup_connector(data_t *data)
>> +{
>> +    if (data->output->pending_crtc) {
>> +        igt_plane_t *primary;
>> +
>> +        primary = igt_output_get_plane_type(data->output,
>> +                            DRM_PLANE_TYPE_PRIMARY);
>> +        igt_plane_set_fb(primary, NULL);
>> +        igt_output_set_crtc(data->output, NULL);
>> +        igt_display_commit2(&data->display, COMMIT_ATOMIC);
>> +    }
>> +
>> +    igt_remove_fb(data->drm_fd, &data->fb);
>> +
>> +    kmstest_force_connector(data->drm_fd,
>> +                data->output->config.connector,
>> +                FORCE_CONNECTOR_UNSPECIFIED);
>> +    kmstest_force_edid(data->drm_fd,
>> +               data->output->config.connector, NULL);
>> +}
>> +
>> +static int try_modeset(data_t *data, const drmModeModeInfo *mode)
>> +{
>> +    igt_plane_t *primary;
>> +    int ret;
>> +
>> +    igt_display_reset(&data->display);
>> +
>> +    igt_output_set_crtc(data->output, data->crtc);
>> +    igt_output_override_mode(data->output, mode);
>> +
>> +    primary = igt_output_get_plane_type(data->output,
>> +                        DRM_PLANE_TYPE_PRIMARY);
>> +
>> +    igt_create_pattern_fb(data->drm_fd,
>> +                  mode->hdisplay, mode->vdisplay,
>> +                  DRM_FORMAT_XRGB8888, DRM_FORMAT_MOD_LINEAR,
>> +                  &data->fb);
>> +    igt_plane_set_fb(primary, &data->fb);
>> +
>> +    ret = igt_display_try_commit_atomic(&data->display,
>> +                        DRM_MODE_ATOMIC_ALLOW_MODESET,
>> +                        NULL);
>> +    if (ret) {
>> +        igt_plane_set_fb(primary, NULL);
>> +        igt_output_set_crtc(data->output, NULL);
>> +        igt_remove_fb(data->drm_fd, &data->fb);
>> +    }
>> +
>> +    return ret;
>> +}
>> +
>> +static bool audio_is_active(void)
>> +{
>> +    if (!eld_is_supported())
>> +        return false;
>> +
>> +    return eld_has_igt();
>> +}
>> +
>> +static unsigned int get_eld_rates(void)
>> +{
>> +    struct eld_entry eld;
>> +
>> +    if (!eld_get_igt(&eld))
>> +        return 0;
>> +
>> +    if (eld.sads_len == 0)
>> +        return 0;
>> +
>> +    return eld.sads[0].rates;
> 
> This is heavily dependent on the semantics that currently we only add 
> one SAD in build_eld. Let's document this atleast.
> 
>> +}
>> +
>> +static void log_eld_rates(unsigned int declared, unsigned int eld_rates)
>> +{
>> +    char decl_str[128], eld_str[128], pruned_str[128];
>> +    unsigned int pruned = declared & ~eld_rates;
>> +
>> +    rates_to_str(declared, decl_str, sizeof(decl_str));
>> +    rates_to_str(eld_rates, eld_str, sizeof(eld_str));
>> +    rates_to_str(pruned, pruned_str, sizeof(pruned_str));
>> +
>> +    igt_info("    SAD declared: %s\n", decl_str);
>> +    igt_info("    ELD reports:  %s\n", eld_str);
>> +    if (pruned)
>> +        igt_info("    Pruned:       %s\n", pruned_str);
>> +}
>> +
>> +static void assert_per_rate(const drmModeModeInfo *mode, int channels,
>> +               int pkts_avail, unsigned int eld_rates)
>> +{
>> +    for (int i = 0; i < ARRAY_SIZE(rate_table); i++) {
>> +        int req = required_pkts_per_line(mode, rate_table[i].freq_hz,
>> +                         channels);
>> +        bool in_eld = eld_rates & rate_table[i].flag;
>> +
>> +        /* A rate that can't fit must not appear in ELD */
>> +        igt_assert_f(!(req > pkts_avail && in_eld),
>> +                 "%s: req=%d > avail=%d but rate present in ELD\n",
>> +                 rate_table[i].name, req, pkts_avail);
> 
> This check does not protect againts cases where the driver over prunes. 
> It asserts true all req <= pkts_avail cases, irrespective of in_eld.
> 
>> +    }
>> +}
>> +
>> +static void log_per_rate_analysis(const drmModeModeInfo *mode,
>> +                  int bpc, int channels,
>> +                  int pkts_avail, unsigned int eld_rates)
>> +{
>> +    const char *layout = (channels <= 2) ? "L0" : "L1";
>> +
>> +    igt_info("    %-6s %-3s  pkts: avail=%d\n",
>> +         "Rate", layout, pkts_avail);
>> +
>> +    for (int i = 0; i < ARRAY_SIZE(rate_table); i++) {
>> +        int req = required_pkts_per_line(mode, rate_table[i].freq_hz,
>> +                         channels);
>> +        const char *expect = (req <= pkts_avail && pkts_avail > 0) ?
>> +                     "fit" : "NO";
>> +        const char *eld_has = (eld_rates & rate_table[i].flag) ?
>> +                     "yes" : "no";
>> +
>> +        igt_info("      %5s: req=%d fit=%s  (ELD: %s)\n",
>> +             rate_table[i].name, req, expect, eld_has);
>> +    }
>> +}
>> +
>> +/* Run the BPC × channels matrix for a given mode/hblank. */
>> +static void test_audio_bw_matrix(data_t *data, const drmModeModeInfo 
>> *mode)
>> +{
>> +    int hblank = hblank_of(mode);
>> +
>> +    igt_info("=== Audio BW matrix: %s hblank=%d ===\n",
>> +         mode->name, hblank);
>> +
>> +    for (int b = 0; b < ARRAY_SIZE(bpc_values); b++) {
>> +        int bpc = bpc_values[b];
>> +
>> +        for (int c = 0; c < ARRAY_SIZE(channel_values); c++) {
>> +            int channels = channel_values[c];
>> +            const struct edid *edid;
>> +            int pkts, ret;
>> +            bool audio;
>> +            unsigned int eld_rates;
>> +
>> +            edid = build_edid(bpc, channels);
>> +            force_edid_and_connector(data, edid);
>> +
>> +            igt_output_set_prop_value(data->output,
>> +                          IGT_CONNECTOR_MAX_BPC, bpc);
>> +
>> +            pkts = avail_pkts_per_line(bpc, hblank);
>> +
>> +            igt_info("\n  %dbpc %dch hblank=%d avail_pkts=%d\n",
>> +                 bpc, channels, hblank, pkts);
>> +
>> +            ret = try_modeset(data, mode);
>> +
>> +            if (ret) {
>> +                igt_info("    modeset: REJECTED\n");
>> +                cleanup_connector(data);
>> +                continue;
>> +            }
>> +
>> +            /* Allow ELD to propagate */
>> +            usleep(200 * 1000);
>> +
>> +            audio = audio_is_active();
>> +            eld_rates = audio ? get_eld_rates() : 0;
>> +
>> +            igt_info("    modeset: OK\n");
>> +            igt_info("    audio:   %s\n", audio ? "active" : 
>> "inactive");
>> +
>> +            igt_assert_f(!(pkts == 0 && audio),
>> +                     "Audio active with 0 available packets\n");
>> +            igt_assert_f(!(pkts > 0 && !audio),
>> +                     "Audio inactive with %d available packets\n",
>> +                     pkts);
>> +
>> +            if (audio) {
>> +                log_eld_rates(ALL_SAMPLE_RATES, eld_rates);
>> +                assert_per_rate(mode, channels, pkts,
>> +                        eld_rates);
>> +            }
>> +
>> +            log_per_rate_analysis(mode, bpc, channels,
>> +                          pkts, eld_rates);
>> +
>> +            cleanup_connector(data);
>> +        }
>> +    }
>> +
>> +    igt_info("\n=== End matrix ===\n");
>> +}
>> +
>> +static void test_audio_bw_supported(data_t *data)
>> +{
>> +    test_audio_bw_matrix(data, &mode_1080p_hblank160);
>> +}
>> +
>> +static void test_audio_bw_pruned(data_t *data)
>> +{
>> +    test_audio_bw_matrix(data, &mode_1080p_hblank80);
>> +}
>> +
>> +static void test_suspend_audio_recovery(data_t *data,
>> +                    enum igt_suspend_state state)
>> +{
>> +    const struct edid *edid;
>> +    bool audio_before, audio_after;
>> +    unsigned int rates_before, rates_after;
>> +    char before_str[128], after_str[128];
>> +    int ret;
>> +
>> +    edid = build_edid(12, 2);
>> +    force_edid_and_connector(data, edid);
>> +
>> +    igt_output_set_prop_value(data->output, IGT_CONNECTOR_MAX_BPC, 12);
>> +
>> +    ret = try_modeset(data, &mode_1080p_hblank80);
>> +    igt_require(ret == 0);
>> +
>> +    usleep(200 * 1000);
> 
> Is this empirical? I understand it is being already being used 
> kms_hdmi_inject but 200ms looks like a lot.
> 
>> +
>> +    audio_before = audio_is_active();
>> +    rates_before = audio_before ? get_eld_rates() : 0;
>> +    rates_to_str(rates_before, before_str, sizeof(before_str));
>> +    igt_info("Before suspend: audio=%d rates=%s\n",
>> +         audio_before, before_str);
>> +
>> +    igt_system_suspend_autoresume(state, SUSPEND_TEST_NONE);
>> +
>> +    usleep(200 * 1000);
>> +
>> +    audio_after = audio_is_active();
>> +    rates_after = audio_after ? get_eld_rates() : 0;
>> +    rates_to_str(rates_after, after_str, sizeof(after_str));
>> +    igt_info("After suspend:  audio=%d rates=%s\n",
>> +         audio_after, after_str);
>> +
>> +    igt_assert_eq(audio_before, audio_after);
>> +    if (audio_before)
>> +        igt_assert_eq(rates_before, rates_after);
>> +
>> +    cleanup_connector(data);
>> +}
>> +
>> +static void test_runtime_suspend_audio(data_t *data)
>> +{
>> +    const struct edid *edid;
>> +    bool audio_before, audio_after;
>> +    unsigned int rates_before, rates_after;
>> +    char before_str[128], after_str[128];
>> +    int ret;
>> +
>> +    edid = build_edid(12, 2);
>> +    force_edid_and_connector(data, edid);
>> +
>> +    igt_output_set_prop_value(data->output, IGT_CONNECTOR_MAX_BPC, 12);
>> +
>> +    ret = try_modeset(data, &mode_1080p_hblank80);
>> +    igt_require(ret == 0);
>> +
>> +    usleep(200 * 1000);
>> +
>> +    audio_before = audio_is_active();
>> +    rates_before = audio_before ? get_eld_rates() : 0;
>> +    rates_to_str(rates_before, before_str, sizeof(before_str));
>> +    igt_info("Before runtime suspend: audio=%d rates=%s\n",
>> +         audio_before, before_str);
>> +
>> +    kmstest_set_connector_dpms(data->drm_fd,
>> +                   data->output->config.connector,
>> +                   DRM_MODE_DPMS_OFF);
>> +    usleep(500 * 1000);
>> +    kmstest_set_connector_dpms(data->drm_fd,
>> +                   data->output->config.connector,
>> +                   DRM_MODE_DPMS_ON);
>> +    usleep(500 * 1000);
>> +
>> +    audio_after = audio_is_active();
>> +    rates_after = audio_after ? get_eld_rates() : 0;
>> +    rates_to_str(rates_after, after_str, sizeof(after_str));
>> +    igt_info("After runtime suspend:  audio=%d rates=%s\n",
>> +         audio_after, after_str);
>> +
>> +    igt_assert_eq(audio_before, audio_after);
>> +    if (audio_before)
>> +        igt_assert_eq(rates_before, rates_after);
>> +
>> +    cleanup_connector(data);
>> +}
> 
> test_suspend_audio_recovery and test_runtime_suspend_audio are almost 
> identical. Can we converge them?
> 
>> +
>> +int igt_main()
>> +{
>> +    data_t data = {};
>> +
>> +    igt_fixture() {
>> +        data.drm_fd = drm_open_driver_master(DRIVER_INTEL | DRIVER_XE);
>> +        igt_require(is_intel_device(data.drm_fd));
>> +        kmstest_set_vt_graphics_mode();
>> +        igt_display_require(&data.display, data.drm_fd);
>> +
>> +        data.output = find_hdmi_output(&data.display);
>> +        igt_require_f(data.output, "No HDMI connector found\n");
>> +
>> +        data.crtc = igt_first_crtc(&data.display);
>> +        igt_require_f(data.crtc, "No usable CRTC found\n");
>> +    }
>> +
>> +    igt_describe("Baseline: hblank=160, audio should be fully 
>> supported "
>> +             "for all BPC and channel configurations.");
>> +    igt_subtest("audio-bw-supported")
>> +        test_audio_bw_supported(&data);
>> +
>> +    igt_describe("Constrained: hblank=80 (CVT RB2), audio may be 
>> pruned "
>> +             "or disabled depending on BPC.");
>> +    igt_subtest("audio-bw-pruned")
>> +        test_audio_bw_pruned(&data);

We have to re-think the sub test names.

audio-bw-supported seems to prune some SADs.

Opened device: /dev/dri/card0
Starting subtest: audio-bw-supported
=== Audio BW matrix: 1920x1080 hblank=160 ===

...

   8bpc 8ch hblank=160 avail_pkts=2
     modeset: OK
     audio:   active
     SAD declared: 32k,44.1k,48k,88k,96k,176k,192k
     ELD reports:  32k,44.1k,48k,88k,96k
     Pruned:       176k,192k
     Rate   L1   pkts: avail=2
         32k: req=1 fit=fit  (ELD: yes)
       44.1k: req=1 fit=fit  (ELD: yes)
         48k: req=1 fit=fit  (ELD: yes)
         88k: req=2 fit=fit  (ELD: yes)
         96k: req=2 fit=fit  (ELD: yes)
        176k: req=3 fit=NO  (ELD: no)
        192k: req=3 fit=NO  (ELD: no)

While audio-bw-pruned has a configuration that prunes nothing.

Starting subtest: audio-bw-pruned
=== Audio BW matrix: 1920x1080 hblank=80 ===

...

   12bpc 2ch hblank=80 avail_pkts=1
     modeset: OK
     audio:   active
     SAD declared: 32k,44.1k,48k,88k,96k,176k,192k
     ELD reports:  32k,44.1k,48k,88k,96k,176k,192k
     Rate   L0   pkts: avail=1
         32k: req=1 fit=fit  (ELD: yes)
       44.1k: req=1 fit=fit  (ELD: yes)
         48k: req=1 fit=fit  (ELD: yes)
         88k: req=1 fit=fit  (ELD: yes)
         96k: req=1 fit=fit  (ELD: yes)
        176k: req=1 fit=fit  (ELD: yes)
        192k: req=1 fit=fit  (ELD: yes)

Either fold both of them to the same subtest or you can have names like

audio-bw-check-rb1 and audio-bw-check-rb2

==
Chaitanya

>> +
>> +    igt_describe("Validate audio recovery after S3 suspend with "
>> +             "constrained hblank.");
>> +    igt_subtest("suspend-s3-audio-recovery")
>> +        test_suspend_audio_recovery(&data, SUSPEND_STATE_MEM);
> 
> The documentation for igt_suspend_state says "A memory sleep (non- 
> hibernation) target state, respecting the system's mem_sleep default" if 
> your intention is to deterministically go to S3 use SUSPEND_STATE_S3 
> instead.
> 
> May I know why only these two power states were selected in particular?
>> +
>> +    igt_describe("Validate audio recovery after S4 hibernate with "
>> +             "constrained hblank.");
>> +    igt_subtest("suspend-s4-audio-recovery")
>> +        test_suspend_audio_recovery(&data, SUSPEND_STATE_DISK);
>> +
>> +    igt_describe("Validate audio recovery after runtime suspend with "
>> +             "constrained hblank.");
>> +    igt_subtest("runtime-suspend-audio-recovery")
>> +        test_runtime_suspend_audio(&data);
>> +
>> +    igt_fixture() {
>> +        igt_display_fini(&data.display);
>> +        drm_close_driver(data.drm_fd);
>> +    }
>> +}
>> diff --git a/tests/meson.build b/tests/meson.build
>> index a62f447df..facb7ab5d 100644
>> --- a/tests/meson.build
>> +++ b/tests/meson.build
>> @@ -259,6 +259,7 @@ intel_kms_progs = [
>>       'kms_fbc_dirty_rect',
>>       'kms_fbcon_fbt',
>>       'kms_fence_pin_leak',
>> +    'kms_hdmi_audio_bw',
> 
> needs to be alphabetical order?
> 
>>       'kms_flip_scaled_crc',
>>       'kms_flip_tiling',
>>       'kms_frontbuffer_tracking',
>