Re: [PATCH v2 2/9] drm/i915: Add get_eld audio component

Daniel Vetter
2015-12-04T10:21:07Z

On Tue, Dec 01, 2015 at 05:09:51PM +0100, Takashi Iwai wrote:
> Implement a new i915_audio_component_ops, get_eld(). It's called by
> the audio driver to fetch the current audio status and ELD of the
> given HDMI/DP port. It returns the size of expected ELD bytes if it's
> valid, zero if no valid ELD is found, or a negative error code. The
> current state of audio on/off is stored in the given pointer, too.
>
> Note that the returned size isn't limited to the given max bytes. If
> the size is greater than the max bytes, it means that only a part of
> ELD has been copied back.
>
> A big warning about the usage of this callback is: you must not call
> it from eld_notify. The eld_notify itself is called in the modeset
> lock, and it leads to a deadlock since get_eld takes the modeset lock,
> too. You need to call get_eld in a work, for example, in such a case.
> We'll see the actual implementation in the later patch in
> sound/pci/hda/patch_hdmi.c.
>
> For achieving this implementation, a new field audio_enabled is added
> to struct intel_digital_port. This is set/reset at each audio
> enable/disable call in intel_audio.c. It's protected with the modeset
> lock as well.
>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
> v1->v2:
> * Use modeset lock for get_eld lock, drop av mutex
> * Return the expected size from get_eld, not the copied size
>
> drivers/gpu/drm/i915/intel_audio.c | 40 ++++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/i915/intel_drv.h | 1 +
> include/drm/i915_component.h | 6 ++++++
> 3 files changed, 47 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
> index 0c38cc6c82ae..1965a61769ea 100644
> --- a/drivers/gpu/drm/i915/intel_audio.c
> +++ b/drivers/gpu/drm/i915/intel_audio.c
> @@ -521,6 +521,7 @@ void intel_audio_codec_enable(struct intel_encoder *intel_encoder)
>
> connector->eld[6] = drm_av_sync_delay(connector, adjusted_mode) / 2;
>
> + intel_dig_port->audio_enabled = true;
> if (dev_priv->display.audio_codec_enable)
> dev_priv->display.audio_codec_enable(connector, intel_encoder,
> adjusted_mode);
> @@ -545,6 +546,7 @@ void intel_audio_codec_disable(struct intel_encoder *intel_encoder)
> struct intel_digital_port *intel_dig_port = enc_to_dig_port(encoder);
> enum port port = intel_dig_port->port;
>
> + intel_dig_port->audio_enabled = false;
> if (dev_priv->display.audio_codec_disable)
> dev_priv->display.audio_codec_disable(intel_encoder);
>
> @@ -702,6 +704,43 @@ static int i915_audio_component_sync_audio_rate(struct device *dev,
> return 0;
> }
>
> +static int i915_audio_component_get_eld(struct device *dev, int port,
> + bool *enabled,
> + unsigned char *buf, int max_bytes)
> +{
> + struct drm_i915_private *dev_priv = dev_to_i915(dev);
> + struct drm_device *drm_dev = dev_priv->dev;
> + struct intel_encoder *intel_encoder;
> + struct intel_digital_port *intel_dig_port;
> + struct drm_connector *connector;
> + unsigned char *eld;
> + int ret = -EINVAL;
> +
> + drm_modeset_lock_all(drm_dev);

This is super expensive and shouldn't ever be used in new code. So either
just the connection_mutex or resurrect the av_mutex and just cache what
you need under that. Tbh I prefer the separate lock + cache for such
specific things since it completely avoids spreading and entangling
locking contexts. We use the same design to get modeset information into
the PSR tracking, FBC tracking and other code which sits between KMS and
other subsystems.

> + for_each_intel_encoder(drm_dev, intel_encoder) {
> + if (intel_encoder->type != INTEL_OUTPUT_DISPLAYPORT &&
> + intel_encoder->type != INTEL_OUTPUT_HDMI)
> + continue;
> + intel_dig_port = enc_to_dig_port(&intel_encoder->base);
> + if (port == intel_dig_port->port) {
> + ret = 0;
> + *enabled = intel_dig_port->audio_enabled;
> + if (!*enabled)
> + break;
> + connector = drm_select_eld(&intel_encoder->base);
> + if (!connector)
> + break;
> + eld = connector->eld;
> + ret = drm_eld_size(eld);
> + memcpy(buf, eld, min(max_bytes, ret));
> + break;
> + }
> + }
> +
> + drm_modeset_unlock_all(drm_dev);
> + return ret;
> +}
> +
> static const struct i915_audio_component_ops i915_audio_component_ops = {
> .owner = THIS_MODULE,
> .get_power = i915_audio_component_get_power,
> @@ -709,6 +748,7 @@ static const struct i915_audio_component_ops i915_audio_component_ops = {
> .codec_wake_override = i915_audio_component_codec_wake_override,
> .get_cdclk_freq = i915_audio_component_get_cdclk_freq,
> .sync_audio_rate = i915_audio_component_sync_audio_rate,
> + .get_eld = i915_audio_component_get_eld,
> };
>
> static int i915_audio_component_bind(struct device *i915_dev,
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 0598932ce623..4afc7560be04 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -798,6 +798,7 @@ struct intel_digital_port {
> u32 saved_port_bits;
> struct intel_dp dp;
> struct intel_hdmi hdmi;
> + bool audio_enabled;
> enum irqreturn (*hpd_pulse)(struct intel_digital_port *, bool);
> bool release_cl2_override;
> };
> diff --git a/include/drm/i915_component.h b/include/drm/i915_component.h
> index 30d89e0da2c6..013779db7d24 100644
> --- a/include/drm/i915_component.h
> +++ b/include/drm/i915_component.h
> @@ -38,6 +38,7 @@
> * @codec_wake_override: Enable/Disable generating the codec wake signal
> * @get_cdclk_freq: get the Core Display Clock in KHz
> * @sync_audio_rate: set n/cts based on the sample rate
> + * @get_eld: fill the audio state and ELD bytes for the given port
> */
> struct i915_audio_component_ops {
> struct module *owner;
> @@ -46,6 +47,8 @@ struct i915_audio_component_ops {
> void (*codec_wake_override)(struct device *, bool enable);
> int (*get_cdclk_freq)(struct device *);
> int (*sync_audio_rate)(struct device *, int port, int rate);
> + int (*get_eld)(struct device *, int port, bool *enabled,
> + unsigned char *buf, int max_bytes);
> };
>
> struct i915_audio_component_audio_ops {
> @@ -55,6 +58,9 @@ struct i915_audio_component_audio_ops {
> * pin sense and/or ELD information has changed.
> * @audio_ptr: HDA driver object
> * @port: Which port has changed (PORTA / PORTB / PORTC etc)
> + *
> + * Note that you can't call i915_audio_component_ops.get_eld directly
> + * from the notifier callback as it may lead to deadlocks.

With av_mutex we don't even need that note here ;-)
-Daniel

> */
> void (*pin_eld_notify)(void *audio_ptr, int port);
> };
> --
> 2.6.3
>
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--
Daniel Vetter
Software Engineer, Intel Corporation