| Message ID | 20250309-drm-hdmi-acr-v1-1-bb9c242f4d4b@linaro.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | drm/display: hdmi: provide common code to get Audio Clock Recovery params | expand |
On Sun, Mar 09, 2025 at 10:13:56AM +0200, Dmitry Baryshkov wrote: > From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > HDMI standard defines recommended N and CTS values for Audio Clock > Regeneration. Currently each driver implements those, frequently in > somewhat unique way. Provide a generic helper for getting those values > to be used by the HDMI drivers. > > The helper is added to drm_hdmi_helper.c rather than drm_hdmi_audio.c > since HDMI drivers can be using this helper function even without > switching to DRM HDMI Audio helpers. > > Note: currently this only handles the values per HDMI 1.4b Section 7.2 > and HDMI 2.0 Section 9.2.1. Later the table can be expanded to > accommodate for Deep Color TMDS char rates per HDMI 1.4 Appendix D > and/or HDMI 2.0 / 2.1 Appendix C). > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > --- > drivers/gpu/drm/display/drm_hdmi_helper.c | 164 ++++++++++++++++++++++++++++++ > include/drm/display/drm_hdmi_helper.h | 6 ++ > 2 files changed, 170 insertions(+) > > diff --git a/drivers/gpu/drm/display/drm_hdmi_helper.c b/drivers/gpu/drm/display/drm_hdmi_helper.c > index 74dd4d01dd9bb2c9e69ec1c60b0056bd69417e8a..89d25571bfd21c56c6835821d2272a12c816a76e 100644 > --- a/drivers/gpu/drm/display/drm_hdmi_helper.c > +++ b/drivers/gpu/drm/display/drm_hdmi_helper.c > @@ -256,3 +256,167 @@ drm_hdmi_compute_mode_clock(const struct drm_display_mode *mode, > return DIV_ROUND_CLOSEST_ULL(clock * bpc, 8); > } > EXPORT_SYMBOL(drm_hdmi_compute_mode_clock); > + > +struct drm_hdmi_acr_n_cts_entry { > + unsigned int n; > + unsigned int cts; > +}; > + > +struct drm_hdmi_acr_data { > + unsigned long tmds_clock_khz; > + struct drm_hdmi_acr_n_cts_entry n_cts_32k, > + n_cts_44k1, > + n_cts_48k; > +}; > + > +static const struct drm_hdmi_acr_data hdmi_acr_n_cts[] = { > + { > + /* "Other" entry */ > + .n_cts_32k = { .n = 4096, }, > + .n_cts_44k1 = { .n = 6272, }, > + .n_cts_48k = { .n = 6144, }, > + }, { > + .tmds_clock_khz = 25175, > + .n_cts_32k = { .n = 4576, .cts = 28125, }, > + .n_cts_44k1 = { .n = 7007, .cts = 31250, }, > + .n_cts_48k = { .n = 6864, .cts = 28125, }, > + }, { > + .tmds_clock_khz = 25200, > + .n_cts_32k = { .n = 4096, .cts = 25200, }, > + .n_cts_44k1 = { .n = 6272, .cts = 28000, }, > + .n_cts_48k = { .n = 6144, .cts = 25200, }, > + }, { > + .tmds_clock_khz = 27000, > + .n_cts_32k = { .n = 4096, .cts = 27000, }, > + .n_cts_44k1 = { .n = 6272, .cts = 30000, }, > + .n_cts_48k = { .n = 6144, .cts = 27000, }, > + }, { > + .tmds_clock_khz = 27027, > + .n_cts_32k = { .n = 4096, .cts = 27027, }, > + .n_cts_44k1 = { .n = 6272, .cts = 30030, }, > + .n_cts_48k = { .n = 6144, .cts = 27027, }, > + }, { > + .tmds_clock_khz = 54000, > + .n_cts_32k = { .n = 4096, .cts = 54000, }, > + .n_cts_44k1 = { .n = 6272, .cts = 60000, }, > + .n_cts_48k = { .n = 6144, .cts = 54000, }, > + }, { > + .tmds_clock_khz = 54054, > + .n_cts_32k = { .n = 4096, .cts = 54054, }, > + .n_cts_44k1 = { .n = 6272, .cts = 60060, }, > + .n_cts_48k = { .n = 6144, .cts = 54054, }, > + }, { > + .tmds_clock_khz = 74176, > + .n_cts_32k = { .n = 11648, .cts = 210937, }, /* and 210938 */ > + .n_cts_44k1 = { .n = 17836, .cts = 234375, }, > + .n_cts_48k = { .n = 11648, .cts = 140625, }, > + }, { > + .tmds_clock_khz = 74250, > + .n_cts_32k = { .n = 4096, .cts = 74250, }, > + .n_cts_44k1 = { .n = 6272, .cts = 82500, }, > + .n_cts_48k = { .n = 6144, .cts = 74250, }, > + }, { > + .tmds_clock_khz = 148352, > + .n_cts_32k = { .n = 11648, .cts = 421875, }, > + .n_cts_44k1 = { .n = 8918, .cts = 234375, }, > + .n_cts_48k = { .n = 5824, .cts = 140625, }, > + }, { > + .tmds_clock_khz = 148500, > + .n_cts_32k = { .n = 4096, .cts = 148500, }, > + .n_cts_44k1 = { .n = 6272, .cts = 165000, }, > + .n_cts_48k = { .n = 6144, .cts = 148500, }, > + }, { > + .tmds_clock_khz = 296703, > + .n_cts_32k = { .n = 5824, .cts = 421875, }, > + .n_cts_44k1 = { .n = 4459, .cts = 234375, }, > + .n_cts_48k = { .n = 5824, .cts = 281250, }, > + }, { > + .tmds_clock_khz = 297000, > + .n_cts_32k = { .n = 3072, .cts = 222750, }, > + .n_cts_44k1 = { .n = 4704, .cts = 247500, }, > + .n_cts_48k = { .n = 5120, .cts = 247500, }, > + }, { > + .tmds_clock_khz = 593407, > + .n_cts_32k = { .n = 5824, .cts = 843750, }, > + .n_cts_44k1 = { .n = 8918, .cts = 937500, }, > + .n_cts_48k = { .n = 5824, .cts = 562500, }, > + }, { > + .tmds_clock_khz = 594000, > + .n_cts_32k = { .n = 3072, .cts = 445500, }, > + .n_cts_44k1 = { .n = 9408, .cts = 990000, }, > + .n_cts_48k = { .n = 6144, .cts = 594000, }, > + }, > +}; > + > +static int drm_hdmi_acr_find_tmds_entry(unsigned long tmds_clock_khz) > +{ > + int i; > + > + /* skip the "other" entry */ > + for (i = 1; i < ARRAY_SIZE(hdmi_acr_n_cts); i++) { > + if (hdmi_acr_n_cts[i].tmds_clock_khz == tmds_clock_khz) > + return i; > + } > + > + return 0; > +} > + > +/** > + * drm_hdmi_acr_get_n_cts() - get N and CTS values for Audio Clock Regeneration > + * > + * @tmds_char_rate: TMDS clock (char rate) as used by the HDMI connector > + * @sample_rate: audio sample rate > + * @out_n: a pointer to write the N value > + * @out_cts: a pointer to write the CTS value > + * > + * Get the N and CTS values (either by calculating them or by returning data > + * from the tables. This follows the HDMI 1.4b Section 7.2 "Audio Sample Clock > + * Capture and Regeneration". > + */ I think we need to make it clear that it's for L-PCM only (I think?), either through a format parameter or through the documentation. > +void > +drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate, > + unsigned int sample_rate, > + unsigned int *out_n, > + unsigned int *out_cts) And we should probably take the connector (or EDID) to make sure the monitor can support the format and sample rates. > +{ > + /* be a bit more tolerant, especially for the 1.001 entries */ > + unsigned long tmds_clock_khz = DIV_ROUND_CLOSEST_ULL(tmds_char_rate, 1000); > + const struct drm_hdmi_acr_n_cts_entry *entry; > + unsigned int n, cts, mult; > + int tmds_idx; > + > + tmds_idx = drm_hdmi_acr_find_tmds_entry(tmds_clock_khz); > + > + /* > + * Don't change the order, 192 kHz is divisible by 48k and 32k, but it > + * should use 48k entry. > + */ > + if (sample_rate % 48000 == 0) { > + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_48k; > + mult = sample_rate / 48000; > + } else if (sample_rate % 44100 == 0) { > + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_44k1; > + mult = sample_rate / 44100; > + } else if (sample_rate % 32000 == 0) { > + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_32k; > + mult = sample_rate / 32000; > + } else { > + entry = NULL; > + } > + > + if (entry) { > + n = entry->n * mult; > + cts = entry->cts; > + } else { > + /* Recommended optimal value, HDMI 1.4b, Section 7.2.1 */ > + n = 128 * sample_rate / 1000; > + cts = 0; > + } > + > + if (!cts) > + cts = DIV_ROUND_CLOSEST_ULL(tmds_char_rate * n, > + 128 * sample_rate); > + > + *out_n = n; > + *out_cts = cts; > +} EXPORT_SYMBOL? Also, I'd really like to have some unit tests for this. Not for all the combinations, obviously, but testing that, say, 44.1kHz with a 148.5 MHz char rate works as expected, and then all the failure conditions depending on the monitor capabilities. Maxime
On Mon, Mar 10, 2025 at 03:46:33PM +0100, Maxime Ripard wrote: > On Sun, Mar 09, 2025 at 10:13:56AM +0200, Dmitry Baryshkov wrote: > > From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > > > HDMI standard defines recommended N and CTS values for Audio Clock > > Regeneration. Currently each driver implements those, frequently in > > somewhat unique way. Provide a generic helper for getting those values > > to be used by the HDMI drivers. > > > > The helper is added to drm_hdmi_helper.c rather than drm_hdmi_audio.c > > since HDMI drivers can be using this helper function even without > > switching to DRM HDMI Audio helpers. > > > > Note: currently this only handles the values per HDMI 1.4b Section 7.2 > > and HDMI 2.0 Section 9.2.1. Later the table can be expanded to > > accommodate for Deep Color TMDS char rates per HDMI 1.4 Appendix D > > and/or HDMI 2.0 / 2.1 Appendix C). > > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > --- > > drivers/gpu/drm/display/drm_hdmi_helper.c | 164 ++++++++++++++++++++++++++++++ > > include/drm/display/drm_hdmi_helper.h | 6 ++ > > 2 files changed, 170 insertions(+) > > > > diff --git a/drivers/gpu/drm/display/drm_hdmi_helper.c b/drivers/gpu/drm/display/drm_hdmi_helper.c > > index 74dd4d01dd9bb2c9e69ec1c60b0056bd69417e8a..89d25571bfd21c56c6835821d2272a12c816a76e 100644 > > --- a/drivers/gpu/drm/display/drm_hdmi_helper.c > > +++ b/drivers/gpu/drm/display/drm_hdmi_helper.c > > @@ -256,3 +256,167 @@ drm_hdmi_compute_mode_clock(const struct drm_display_mode *mode, > > return DIV_ROUND_CLOSEST_ULL(clock * bpc, 8); > > } > > EXPORT_SYMBOL(drm_hdmi_compute_mode_clock); > > + > > +struct drm_hdmi_acr_n_cts_entry { > > + unsigned int n; > > + unsigned int cts; > > +}; > > + > > +struct drm_hdmi_acr_data { > > + unsigned long tmds_clock_khz; > > + struct drm_hdmi_acr_n_cts_entry n_cts_32k, > > + n_cts_44k1, > > + n_cts_48k; > > +}; > > + > > +static const struct drm_hdmi_acr_data hdmi_acr_n_cts[] = { > > + { > > + /* "Other" entry */ > > + .n_cts_32k = { .n = 4096, }, > > + .n_cts_44k1 = { .n = 6272, }, > > + .n_cts_48k = { .n = 6144, }, > > + }, { > > + .tmds_clock_khz = 25175, > > + .n_cts_32k = { .n = 4576, .cts = 28125, }, > > + .n_cts_44k1 = { .n = 7007, .cts = 31250, }, > > + .n_cts_48k = { .n = 6864, .cts = 28125, }, > > + }, { > > + .tmds_clock_khz = 25200, > > + .n_cts_32k = { .n = 4096, .cts = 25200, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 28000, }, > > + .n_cts_48k = { .n = 6144, .cts = 25200, }, > > + }, { > > + .tmds_clock_khz = 27000, > > + .n_cts_32k = { .n = 4096, .cts = 27000, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 30000, }, > > + .n_cts_48k = { .n = 6144, .cts = 27000, }, > > + }, { > > + .tmds_clock_khz = 27027, > > + .n_cts_32k = { .n = 4096, .cts = 27027, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 30030, }, > > + .n_cts_48k = { .n = 6144, .cts = 27027, }, > > + }, { > > + .tmds_clock_khz = 54000, > > + .n_cts_32k = { .n = 4096, .cts = 54000, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 60000, }, > > + .n_cts_48k = { .n = 6144, .cts = 54000, }, > > + }, { > > + .tmds_clock_khz = 54054, > > + .n_cts_32k = { .n = 4096, .cts = 54054, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 60060, }, > > + .n_cts_48k = { .n = 6144, .cts = 54054, }, > > + }, { > > + .tmds_clock_khz = 74176, > > + .n_cts_32k = { .n = 11648, .cts = 210937, }, /* and 210938 */ > > + .n_cts_44k1 = { .n = 17836, .cts = 234375, }, > > + .n_cts_48k = { .n = 11648, .cts = 140625, }, > > + }, { > > + .tmds_clock_khz = 74250, > > + .n_cts_32k = { .n = 4096, .cts = 74250, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 82500, }, > > + .n_cts_48k = { .n = 6144, .cts = 74250, }, > > + }, { > > + .tmds_clock_khz = 148352, > > + .n_cts_32k = { .n = 11648, .cts = 421875, }, > > + .n_cts_44k1 = { .n = 8918, .cts = 234375, }, > > + .n_cts_48k = { .n = 5824, .cts = 140625, }, > > + }, { > > + .tmds_clock_khz = 148500, > > + .n_cts_32k = { .n = 4096, .cts = 148500, }, > > + .n_cts_44k1 = { .n = 6272, .cts = 165000, }, > > + .n_cts_48k = { .n = 6144, .cts = 148500, }, > > + }, { > > + .tmds_clock_khz = 296703, > > + .n_cts_32k = { .n = 5824, .cts = 421875, }, > > + .n_cts_44k1 = { .n = 4459, .cts = 234375, }, > > + .n_cts_48k = { .n = 5824, .cts = 281250, }, > > + }, { > > + .tmds_clock_khz = 297000, > > + .n_cts_32k = { .n = 3072, .cts = 222750, }, > > + .n_cts_44k1 = { .n = 4704, .cts = 247500, }, > > + .n_cts_48k = { .n = 5120, .cts = 247500, }, > > + }, { > > + .tmds_clock_khz = 593407, > > + .n_cts_32k = { .n = 5824, .cts = 843750, }, > > + .n_cts_44k1 = { .n = 8918, .cts = 937500, }, > > + .n_cts_48k = { .n = 5824, .cts = 562500, }, > > + }, { > > + .tmds_clock_khz = 594000, > > + .n_cts_32k = { .n = 3072, .cts = 445500, }, > > + .n_cts_44k1 = { .n = 9408, .cts = 990000, }, > > + .n_cts_48k = { .n = 6144, .cts = 594000, }, > > + }, > > +}; > > + > > +static int drm_hdmi_acr_find_tmds_entry(unsigned long tmds_clock_khz) > > +{ > > + int i; > > + > > + /* skip the "other" entry */ > > + for (i = 1; i < ARRAY_SIZE(hdmi_acr_n_cts); i++) { > > + if (hdmi_acr_n_cts[i].tmds_clock_khz == tmds_clock_khz) > > + return i; > > + } > > + > > + return 0; > > +} > > + > > +/** > > + * drm_hdmi_acr_get_n_cts() - get N and CTS values for Audio Clock Regeneration > > + * > > + * @tmds_char_rate: TMDS clock (char rate) as used by the HDMI connector > > + * @sample_rate: audio sample rate > > + * @out_n: a pointer to write the N value > > + * @out_cts: a pointer to write the CTS value > > + * > > + * Get the N and CTS values (either by calculating them or by returning data > > + * from the tables. This follows the HDMI 1.4b Section 7.2 "Audio Sample Clock > > + * Capture and Regeneration". > > + */ > > I think we need to make it clear that it's for L-PCM only (I think?), > either through a format parameter or through the documentation. Ack > > > +void > > +drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate, > > + unsigned int sample_rate, > > + unsigned int *out_n, > > + unsigned int *out_cts) > > And we should probably take the connector (or EDID) to make sure the > monitor can support the format and sample rates. Interesting perspective, I'll give it a thought. I was really just trying to get rid of the duplication. I think that 'supported' parts should be implemented in the hdmi-codec instead, parsing the ELD and updating hw constraints. WDYT? > > > +{ > > + /* be a bit more tolerant, especially for the 1.001 entries */ > > + unsigned long tmds_clock_khz = DIV_ROUND_CLOSEST_ULL(tmds_char_rate, 1000); > > + const struct drm_hdmi_acr_n_cts_entry *entry; > > + unsigned int n, cts, mult; > > + int tmds_idx; > > + > > + tmds_idx = drm_hdmi_acr_find_tmds_entry(tmds_clock_khz); > > + > > + /* > > + * Don't change the order, 192 kHz is divisible by 48k and 32k, but it > > + * should use 48k entry. > > + */ > > + if (sample_rate % 48000 == 0) { > > + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_48k; > > + mult = sample_rate / 48000; > > + } else if (sample_rate % 44100 == 0) { > > + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_44k1; > > + mult = sample_rate / 44100; > > + } else if (sample_rate % 32000 == 0) { > > + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_32k; > > + mult = sample_rate / 32000; > > + } else { > > + entry = NULL; > > + } > > + > > + if (entry) { > > + n = entry->n * mult; > > + cts = entry->cts; > > + } else { > > + /* Recommended optimal value, HDMI 1.4b, Section 7.2.1 */ > > + n = 128 * sample_rate / 1000; > > + cts = 0; > > + } > > + > > + if (!cts) > > + cts = DIV_ROUND_CLOSEST_ULL(tmds_char_rate * n, > > + 128 * sample_rate); > > + > > + *out_n = n; > > + *out_cts = cts; > > +} > > EXPORT_SYMBOL? Yes, I forgot it. > > Also, I'd really like to have some unit tests for this. Not for all the > combinations, obviously, but testing that, say, 44.1kHz with a 148.5 MHz > char rate works as expected, and then all the failure conditions > depending on the monitor capabilities. Ack for the tests. For the monitor capabilities, let's finish the discussion above first.
On Mon, Mar 10, 2025 at 10:14:52PM +0200, Dmitry Baryshkov wrote: > On Mon, Mar 10, 2025 at 03:46:33PM +0100, Maxime Ripard wrote: > > On Sun, Mar 09, 2025 at 10:13:56AM +0200, Dmitry Baryshkov wrote: > > > From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > > > > > HDMI standard defines recommended N and CTS values for Audio Clock > > > Regeneration. Currently each driver implements those, frequently in > > > somewhat unique way. Provide a generic helper for getting those values > > > to be used by the HDMI drivers. > > > > > > The helper is added to drm_hdmi_helper.c rather than drm_hdmi_audio.c > > > since HDMI drivers can be using this helper function even without > > > switching to DRM HDMI Audio helpers. > > > > > > Note: currently this only handles the values per HDMI 1.4b Section 7.2 > > > and HDMI 2.0 Section 9.2.1. Later the table can be expanded to > > > accommodate for Deep Color TMDS char rates per HDMI 1.4 Appendix D > > > and/or HDMI 2.0 / 2.1 Appendix C). > > > > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > > --- > > > drivers/gpu/drm/display/drm_hdmi_helper.c | 164 ++++++++++++++++++++++++++++++ > > > include/drm/display/drm_hdmi_helper.h | 6 ++ > > > 2 files changed, 170 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/display/drm_hdmi_helper.c b/drivers/gpu/drm/display/drm_hdmi_helper.c > > > index 74dd4d01dd9bb2c9e69ec1c60b0056bd69417e8a..89d25571bfd21c56c6835821d2272a12c816a76e 100644 > > > --- a/drivers/gpu/drm/display/drm_hdmi_helper.c > > > +++ b/drivers/gpu/drm/display/drm_hdmi_helper.c > > > @@ -256,3 +256,167 @@ drm_hdmi_compute_mode_clock(const struct drm_display_mode *mode, > > > return DIV_ROUND_CLOSEST_ULL(clock * bpc, 8); > > > } > > > EXPORT_SYMBOL(drm_hdmi_compute_mode_clock); > > > + > > > +struct drm_hdmi_acr_n_cts_entry { > > > + unsigned int n; > > > + unsigned int cts; > > > +}; > > > + > > > +struct drm_hdmi_acr_data { > > > + unsigned long tmds_clock_khz; > > > + struct drm_hdmi_acr_n_cts_entry n_cts_32k, > > > + n_cts_44k1, > > > + n_cts_48k; > > > +}; > > > + > > > +static const struct drm_hdmi_acr_data hdmi_acr_n_cts[] = { > > > + { > > > + /* "Other" entry */ > > > + .n_cts_32k = { .n = 4096, }, > > > + .n_cts_44k1 = { .n = 6272, }, > > > + .n_cts_48k = { .n = 6144, }, > > > + }, { > > > + .tmds_clock_khz = 25175, > > > + .n_cts_32k = { .n = 4576, .cts = 28125, }, > > > + .n_cts_44k1 = { .n = 7007, .cts = 31250, }, > > > + .n_cts_48k = { .n = 6864, .cts = 28125, }, > > > + }, { > > > + .tmds_clock_khz = 25200, > > > + .n_cts_32k = { .n = 4096, .cts = 25200, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 28000, }, > > > + .n_cts_48k = { .n = 6144, .cts = 25200, }, > > > + }, { > > > + .tmds_clock_khz = 27000, > > > + .n_cts_32k = { .n = 4096, .cts = 27000, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 30000, }, > > > + .n_cts_48k = { .n = 6144, .cts = 27000, }, > > > + }, { > > > + .tmds_clock_khz = 27027, > > > + .n_cts_32k = { .n = 4096, .cts = 27027, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 30030, }, > > > + .n_cts_48k = { .n = 6144, .cts = 27027, }, > > > + }, { > > > + .tmds_clock_khz = 54000, > > > + .n_cts_32k = { .n = 4096, .cts = 54000, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 60000, }, > > > + .n_cts_48k = { .n = 6144, .cts = 54000, }, > > > + }, { > > > + .tmds_clock_khz = 54054, > > > + .n_cts_32k = { .n = 4096, .cts = 54054, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 60060, }, > > > + .n_cts_48k = { .n = 6144, .cts = 54054, }, > > > + }, { > > > + .tmds_clock_khz = 74176, > > > + .n_cts_32k = { .n = 11648, .cts = 210937, }, /* and 210938 */ > > > + .n_cts_44k1 = { .n = 17836, .cts = 234375, }, > > > + .n_cts_48k = { .n = 11648, .cts = 140625, }, > > > + }, { > > > + .tmds_clock_khz = 74250, > > > + .n_cts_32k = { .n = 4096, .cts = 74250, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 82500, }, > > > + .n_cts_48k = { .n = 6144, .cts = 74250, }, > > > + }, { > > > + .tmds_clock_khz = 148352, > > > + .n_cts_32k = { .n = 11648, .cts = 421875, }, > > > + .n_cts_44k1 = { .n = 8918, .cts = 234375, }, > > > + .n_cts_48k = { .n = 5824, .cts = 140625, }, > > > + }, { > > > + .tmds_clock_khz = 148500, > > > + .n_cts_32k = { .n = 4096, .cts = 148500, }, > > > + .n_cts_44k1 = { .n = 6272, .cts = 165000, }, > > > + .n_cts_48k = { .n = 6144, .cts = 148500, }, > > > + }, { > > > + .tmds_clock_khz = 296703, > > > + .n_cts_32k = { .n = 5824, .cts = 421875, }, > > > + .n_cts_44k1 = { .n = 4459, .cts = 234375, }, > > > + .n_cts_48k = { .n = 5824, .cts = 281250, }, > > > + }, { > > > + .tmds_clock_khz = 297000, > > > + .n_cts_32k = { .n = 3072, .cts = 222750, }, > > > + .n_cts_44k1 = { .n = 4704, .cts = 247500, }, > > > + .n_cts_48k = { .n = 5120, .cts = 247500, }, > > > + }, { > > > + .tmds_clock_khz = 593407, > > > + .n_cts_32k = { .n = 5824, .cts = 843750, }, > > > + .n_cts_44k1 = { .n = 8918, .cts = 937500, }, > > > + .n_cts_48k = { .n = 5824, .cts = 562500, }, > > > + }, { > > > + .tmds_clock_khz = 594000, > > > + .n_cts_32k = { .n = 3072, .cts = 445500, }, > > > + .n_cts_44k1 = { .n = 9408, .cts = 990000, }, > > > + .n_cts_48k = { .n = 6144, .cts = 594000, }, > > > + }, > > > +}; > > > + > > > +static int drm_hdmi_acr_find_tmds_entry(unsigned long tmds_clock_khz) > > > +{ > > > + int i; > > > + > > > + /* skip the "other" entry */ > > > + for (i = 1; i < ARRAY_SIZE(hdmi_acr_n_cts); i++) { > > > + if (hdmi_acr_n_cts[i].tmds_clock_khz == tmds_clock_khz) > > > + return i; > > > + } > > > + > > > + return 0; > > > +} > > > + > > > +/** > > > + * drm_hdmi_acr_get_n_cts() - get N and CTS values for Audio Clock Regeneration > > > + * > > > + * @tmds_char_rate: TMDS clock (char rate) as used by the HDMI connector > > > + * @sample_rate: audio sample rate > > > + * @out_n: a pointer to write the N value > > > + * @out_cts: a pointer to write the CTS value > > > + * > > > + * Get the N and CTS values (either by calculating them or by returning data > > > + * from the tables. This follows the HDMI 1.4b Section 7.2 "Audio Sample Clock > > > + * Capture and Regeneration". > > > + */ > > > > I think we need to make it clear that it's for L-PCM only (I think?), > > either through a format parameter or through the documentation. > > Ack > > > > > > +void > > > +drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate, > > > + unsigned int sample_rate, > > > + unsigned int *out_n, > > > + unsigned int *out_cts) > > > > And we should probably take the connector (or EDID) to make sure the > > monitor can support the format and sample rates. > > Interesting perspective, I'll give it a thought. I was really just > trying to get rid of the duplication. > > I think that 'supported' parts should be implemented in the hdmi-codec > instead, parsing the ELD and updating hw constraints. WDYT? Basically, I want to make sure we cover section 7.3 of HDMI 1.4, ie, make sure we can't end up (or validate) in a situation that isn't allowed by the spec. If ALSA covers it already, then I guess it's fine, but we should document it and point to where it's dealt with. Maxime
On Tue, Mar 11, 2025 at 08:59:45AM +0100, Maxime Ripard wrote: > On Mon, Mar 10, 2025 at 10:14:52PM +0200, Dmitry Baryshkov wrote: > > On Mon, Mar 10, 2025 at 03:46:33PM +0100, Maxime Ripard wrote: > > > On Sun, Mar 09, 2025 at 10:13:56AM +0200, Dmitry Baryshkov wrote: > > > > From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > > > > > > > HDMI standard defines recommended N and CTS values for Audio Clock > > > > Regeneration. Currently each driver implements those, frequently in > > > > somewhat unique way. Provide a generic helper for getting those values > > > > to be used by the HDMI drivers. > > > > > > > > The helper is added to drm_hdmi_helper.c rather than drm_hdmi_audio.c > > > > since HDMI drivers can be using this helper function even without > > > > switching to DRM HDMI Audio helpers. > > > > > > > > Note: currently this only handles the values per HDMI 1.4b Section 7.2 > > > > and HDMI 2.0 Section 9.2.1. Later the table can be expanded to > > > > accommodate for Deep Color TMDS char rates per HDMI 1.4 Appendix D > > > > and/or HDMI 2.0 / 2.1 Appendix C). > > > > > > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > > > > --- > > > > drivers/gpu/drm/display/drm_hdmi_helper.c | 164 ++++++++++++++++++++++++++++++ > > > > include/drm/display/drm_hdmi_helper.h | 6 ++ > > > > 2 files changed, 170 insertions(+) > > > > > > > > diff --git a/drivers/gpu/drm/display/drm_hdmi_helper.c b/drivers/gpu/drm/display/drm_hdmi_helper.c > > > > index 74dd4d01dd9bb2c9e69ec1c60b0056bd69417e8a..89d25571bfd21c56c6835821d2272a12c816a76e 100644 > > > > --- a/drivers/gpu/drm/display/drm_hdmi_helper.c > > > > +++ b/drivers/gpu/drm/display/drm_hdmi_helper.c > > > > @@ -256,3 +256,167 @@ drm_hdmi_compute_mode_clock(const struct drm_display_mode *mode, > > > > return DIV_ROUND_CLOSEST_ULL(clock * bpc, 8); > > > > } > > > > EXPORT_SYMBOL(drm_hdmi_compute_mode_clock); > > > > + > > > > +struct drm_hdmi_acr_n_cts_entry { > > > > + unsigned int n; > > > > + unsigned int cts; > > > > +}; > > > > + > > > > +struct drm_hdmi_acr_data { > > > > + unsigned long tmds_clock_khz; > > > > + struct drm_hdmi_acr_n_cts_entry n_cts_32k, > > > > + n_cts_44k1, > > > > + n_cts_48k; > > > > +}; > > > > + > > > > +static const struct drm_hdmi_acr_data hdmi_acr_n_cts[] = { > > > > + { > > > > + /* "Other" entry */ > > > > + .n_cts_32k = { .n = 4096, }, > > > > + .n_cts_44k1 = { .n = 6272, }, > > > > + .n_cts_48k = { .n = 6144, }, > > > > + }, { > > > > + .tmds_clock_khz = 25175, > > > > + .n_cts_32k = { .n = 4576, .cts = 28125, }, > > > > + .n_cts_44k1 = { .n = 7007, .cts = 31250, }, > > > > + .n_cts_48k = { .n = 6864, .cts = 28125, }, > > > > + }, { > > > > + .tmds_clock_khz = 25200, > > > > + .n_cts_32k = { .n = 4096, .cts = 25200, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 28000, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 25200, }, > > > > + }, { > > > > + .tmds_clock_khz = 27000, > > > > + .n_cts_32k = { .n = 4096, .cts = 27000, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 30000, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 27000, }, > > > > + }, { > > > > + .tmds_clock_khz = 27027, > > > > + .n_cts_32k = { .n = 4096, .cts = 27027, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 30030, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 27027, }, > > > > + }, { > > > > + .tmds_clock_khz = 54000, > > > > + .n_cts_32k = { .n = 4096, .cts = 54000, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 60000, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 54000, }, > > > > + }, { > > > > + .tmds_clock_khz = 54054, > > > > + .n_cts_32k = { .n = 4096, .cts = 54054, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 60060, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 54054, }, > > > > + }, { > > > > + .tmds_clock_khz = 74176, > > > > + .n_cts_32k = { .n = 11648, .cts = 210937, }, /* and 210938 */ > > > > + .n_cts_44k1 = { .n = 17836, .cts = 234375, }, > > > > + .n_cts_48k = { .n = 11648, .cts = 140625, }, > > > > + }, { > > > > + .tmds_clock_khz = 74250, > > > > + .n_cts_32k = { .n = 4096, .cts = 74250, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 82500, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 74250, }, > > > > + }, { > > > > + .tmds_clock_khz = 148352, > > > > + .n_cts_32k = { .n = 11648, .cts = 421875, }, > > > > + .n_cts_44k1 = { .n = 8918, .cts = 234375, }, > > > > + .n_cts_48k = { .n = 5824, .cts = 140625, }, > > > > + }, { > > > > + .tmds_clock_khz = 148500, > > > > + .n_cts_32k = { .n = 4096, .cts = 148500, }, > > > > + .n_cts_44k1 = { .n = 6272, .cts = 165000, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 148500, }, > > > > + }, { > > > > + .tmds_clock_khz = 296703, > > > > + .n_cts_32k = { .n = 5824, .cts = 421875, }, > > > > + .n_cts_44k1 = { .n = 4459, .cts = 234375, }, > > > > + .n_cts_48k = { .n = 5824, .cts = 281250, }, > > > > + }, { > > > > + .tmds_clock_khz = 297000, > > > > + .n_cts_32k = { .n = 3072, .cts = 222750, }, > > > > + .n_cts_44k1 = { .n = 4704, .cts = 247500, }, > > > > + .n_cts_48k = { .n = 5120, .cts = 247500, }, > > > > + }, { > > > > + .tmds_clock_khz = 593407, > > > > + .n_cts_32k = { .n = 5824, .cts = 843750, }, > > > > + .n_cts_44k1 = { .n = 8918, .cts = 937500, }, > > > > + .n_cts_48k = { .n = 5824, .cts = 562500, }, > > > > + }, { > > > > + .tmds_clock_khz = 594000, > > > > + .n_cts_32k = { .n = 3072, .cts = 445500, }, > > > > + .n_cts_44k1 = { .n = 9408, .cts = 990000, }, > > > > + .n_cts_48k = { .n = 6144, .cts = 594000, }, > > > > + }, > > > > +}; > > > > + > > > > +static int drm_hdmi_acr_find_tmds_entry(unsigned long tmds_clock_khz) > > > > +{ > > > > + int i; > > > > + > > > > + /* skip the "other" entry */ > > > > + for (i = 1; i < ARRAY_SIZE(hdmi_acr_n_cts); i++) { > > > > + if (hdmi_acr_n_cts[i].tmds_clock_khz == tmds_clock_khz) > > > > + return i; > > > > + } > > > > + > > > > + return 0; > > > > +} > > > > + > > > > +/** > > > > + * drm_hdmi_acr_get_n_cts() - get N and CTS values for Audio Clock Regeneration > > > > + * > > > > + * @tmds_char_rate: TMDS clock (char rate) as used by the HDMI connector > > > > + * @sample_rate: audio sample rate > > > > + * @out_n: a pointer to write the N value > > > > + * @out_cts: a pointer to write the CTS value > > > > + * > > > > + * Get the N and CTS values (either by calculating them or by returning data > > > > + * from the tables. This follows the HDMI 1.4b Section 7.2 "Audio Sample Clock > > > > + * Capture and Regeneration". > > > > + */ > > > > > > I think we need to make it clear that it's for L-PCM only (I think?), > > > either through a format parameter or through the documentation. > > > > Ack > > > > > > > > > +void > > > > +drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate, > > > > + unsigned int sample_rate, > > > > + unsigned int *out_n, > > > > + unsigned int *out_cts) > > > > > > And we should probably take the connector (or EDID) to make sure the > > > monitor can support the format and sample rates. > > > > Interesting perspective, I'll give it a thought. I was really just > > trying to get rid of the duplication. > > > > I think that 'supported' parts should be implemented in the hdmi-codec > > instead, parsing the ELD and updating hw constraints. WDYT? > > Basically, I want to make sure we cover section 7.3 of HDMI 1.4, ie, > make sure we can't end up (or validate) in a situation that isn't > allowed by the spec. I think that's a question for a separate function. This one really targets 7.2 rather than 7.3. > If ALSA covers it already, then I guess it's fine, but we should > document it and point to where it's dealt with. I'm not sure if it covers that right now, but it should be handled on ALSA side. For example, see sound/pci/hda/patch_hdmi.c, I think it is handling those bits. We are providing ELD to hdmi-codec, it can implement and propagate HW constraints.
diff --git a/drivers/gpu/drm/display/drm_hdmi_helper.c b/drivers/gpu/drm/display/drm_hdmi_helper.c index 74dd4d01dd9bb2c9e69ec1c60b0056bd69417e8a..89d25571bfd21c56c6835821d2272a12c816a76e 100644 --- a/drivers/gpu/drm/display/drm_hdmi_helper.c +++ b/drivers/gpu/drm/display/drm_hdmi_helper.c @@ -256,3 +256,167 @@ drm_hdmi_compute_mode_clock(const struct drm_display_mode *mode, return DIV_ROUND_CLOSEST_ULL(clock * bpc, 8); } EXPORT_SYMBOL(drm_hdmi_compute_mode_clock); + +struct drm_hdmi_acr_n_cts_entry { + unsigned int n; + unsigned int cts; +}; + +struct drm_hdmi_acr_data { + unsigned long tmds_clock_khz; + struct drm_hdmi_acr_n_cts_entry n_cts_32k, + n_cts_44k1, + n_cts_48k; +}; + +static const struct drm_hdmi_acr_data hdmi_acr_n_cts[] = { + { + /* "Other" entry */ + .n_cts_32k = { .n = 4096, }, + .n_cts_44k1 = { .n = 6272, }, + .n_cts_48k = { .n = 6144, }, + }, { + .tmds_clock_khz = 25175, + .n_cts_32k = { .n = 4576, .cts = 28125, }, + .n_cts_44k1 = { .n = 7007, .cts = 31250, }, + .n_cts_48k = { .n = 6864, .cts = 28125, }, + }, { + .tmds_clock_khz = 25200, + .n_cts_32k = { .n = 4096, .cts = 25200, }, + .n_cts_44k1 = { .n = 6272, .cts = 28000, }, + .n_cts_48k = { .n = 6144, .cts = 25200, }, + }, { + .tmds_clock_khz = 27000, + .n_cts_32k = { .n = 4096, .cts = 27000, }, + .n_cts_44k1 = { .n = 6272, .cts = 30000, }, + .n_cts_48k = { .n = 6144, .cts = 27000, }, + }, { + .tmds_clock_khz = 27027, + .n_cts_32k = { .n = 4096, .cts = 27027, }, + .n_cts_44k1 = { .n = 6272, .cts = 30030, }, + .n_cts_48k = { .n = 6144, .cts = 27027, }, + }, { + .tmds_clock_khz = 54000, + .n_cts_32k = { .n = 4096, .cts = 54000, }, + .n_cts_44k1 = { .n = 6272, .cts = 60000, }, + .n_cts_48k = { .n = 6144, .cts = 54000, }, + }, { + .tmds_clock_khz = 54054, + .n_cts_32k = { .n = 4096, .cts = 54054, }, + .n_cts_44k1 = { .n = 6272, .cts = 60060, }, + .n_cts_48k = { .n = 6144, .cts = 54054, }, + }, { + .tmds_clock_khz = 74176, + .n_cts_32k = { .n = 11648, .cts = 210937, }, /* and 210938 */ + .n_cts_44k1 = { .n = 17836, .cts = 234375, }, + .n_cts_48k = { .n = 11648, .cts = 140625, }, + }, { + .tmds_clock_khz = 74250, + .n_cts_32k = { .n = 4096, .cts = 74250, }, + .n_cts_44k1 = { .n = 6272, .cts = 82500, }, + .n_cts_48k = { .n = 6144, .cts = 74250, }, + }, { + .tmds_clock_khz = 148352, + .n_cts_32k = { .n = 11648, .cts = 421875, }, + .n_cts_44k1 = { .n = 8918, .cts = 234375, }, + .n_cts_48k = { .n = 5824, .cts = 140625, }, + }, { + .tmds_clock_khz = 148500, + .n_cts_32k = { .n = 4096, .cts = 148500, }, + .n_cts_44k1 = { .n = 6272, .cts = 165000, }, + .n_cts_48k = { .n = 6144, .cts = 148500, }, + }, { + .tmds_clock_khz = 296703, + .n_cts_32k = { .n = 5824, .cts = 421875, }, + .n_cts_44k1 = { .n = 4459, .cts = 234375, }, + .n_cts_48k = { .n = 5824, .cts = 281250, }, + }, { + .tmds_clock_khz = 297000, + .n_cts_32k = { .n = 3072, .cts = 222750, }, + .n_cts_44k1 = { .n = 4704, .cts = 247500, }, + .n_cts_48k = { .n = 5120, .cts = 247500, }, + }, { + .tmds_clock_khz = 593407, + .n_cts_32k = { .n = 5824, .cts = 843750, }, + .n_cts_44k1 = { .n = 8918, .cts = 937500, }, + .n_cts_48k = { .n = 5824, .cts = 562500, }, + }, { + .tmds_clock_khz = 594000, + .n_cts_32k = { .n = 3072, .cts = 445500, }, + .n_cts_44k1 = { .n = 9408, .cts = 990000, }, + .n_cts_48k = { .n = 6144, .cts = 594000, }, + }, +}; + +static int drm_hdmi_acr_find_tmds_entry(unsigned long tmds_clock_khz) +{ + int i; + + /* skip the "other" entry */ + for (i = 1; i < ARRAY_SIZE(hdmi_acr_n_cts); i++) { + if (hdmi_acr_n_cts[i].tmds_clock_khz == tmds_clock_khz) + return i; + } + + return 0; +} + +/** + * drm_hdmi_acr_get_n_cts() - get N and CTS values for Audio Clock Regeneration + * + * @tmds_char_rate: TMDS clock (char rate) as used by the HDMI connector + * @sample_rate: audio sample rate + * @out_n: a pointer to write the N value + * @out_cts: a pointer to write the CTS value + * + * Get the N and CTS values (either by calculating them or by returning data + * from the tables. This follows the HDMI 1.4b Section 7.2 "Audio Sample Clock + * Capture and Regeneration". + */ +void +drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate, + unsigned int sample_rate, + unsigned int *out_n, + unsigned int *out_cts) +{ + /* be a bit more tolerant, especially for the 1.001 entries */ + unsigned long tmds_clock_khz = DIV_ROUND_CLOSEST_ULL(tmds_char_rate, 1000); + const struct drm_hdmi_acr_n_cts_entry *entry; + unsigned int n, cts, mult; + int tmds_idx; + + tmds_idx = drm_hdmi_acr_find_tmds_entry(tmds_clock_khz); + + /* + * Don't change the order, 192 kHz is divisible by 48k and 32k, but it + * should use 48k entry. + */ + if (sample_rate % 48000 == 0) { + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_48k; + mult = sample_rate / 48000; + } else if (sample_rate % 44100 == 0) { + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_44k1; + mult = sample_rate / 44100; + } else if (sample_rate % 32000 == 0) { + entry = &hdmi_acr_n_cts[tmds_idx].n_cts_32k; + mult = sample_rate / 32000; + } else { + entry = NULL; + } + + if (entry) { + n = entry->n * mult; + cts = entry->cts; + } else { + /* Recommended optimal value, HDMI 1.4b, Section 7.2.1 */ + n = 128 * sample_rate / 1000; + cts = 0; + } + + if (!cts) + cts = DIV_ROUND_CLOSEST_ULL(tmds_char_rate * n, + 128 * sample_rate); + + *out_n = n; + *out_cts = cts; +} diff --git a/include/drm/display/drm_hdmi_helper.h b/include/drm/display/drm_hdmi_helper.h index 57e3b18c15ec79636d89267aba0e88f434c5d4db..09145c9ee9fc0cd839242f2373b305940e06e157 100644 --- a/include/drm/display/drm_hdmi_helper.h +++ b/include/drm/display/drm_hdmi_helper.h @@ -28,4 +28,10 @@ unsigned long long drm_hdmi_compute_mode_clock(const struct drm_display_mode *mode, unsigned int bpc, enum hdmi_colorspace fmt); +void +drm_hdmi_acr_get_n_cts(unsigned long long tmds_char_rate, + unsigned int sample_rate, + unsigned int *out_n, + unsigned int *out_cts); + #endif