Hi Russell,
On 03/30/2015 03:40 PM, Russell King wrote:
> iMX6 devices from an errata (ERR005174) where the audio FIFO can be
> emptied while it is partially full, resulting in misalignment of the
> audio samples.
>
> To prevent this, the errata workaround recommends writing N as zero
> until the audio FIFO has been loaded by DMA. Writing N=0 prevents the
> HDMI bridge from reading from the audio FIFO, effectively disabling
> audio.
>
> This means we need to provide the audio driver with a pair of functions
> to enable/disable audio. These are dw_hdmi_audio_enable() and
> dw_hdmi_audio_disable().
>
> A spinlock is introduced to ensure that setting the CTS/N values can't
> race, ensuring that the audio driver calling the enable/disable
> functions (which are called in an atomic context) can't race with a
> modeset.
>
> Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> ---
> drivers/gpu/drm/bridge/dw_hdmi.c | 34 +++++++++++++++++++++++++++++++++-
> include/drm/bridge/dw_hdmi.h | 2 ++
> 2 files changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c
> b/drivers/gpu/drm/bridge/dw_hdmi.c
> index 245d17e58dec..67f07d15c12b 100644
> --- a/drivers/gpu/drm/bridge/dw_hdmi.c
> +++ b/drivers/gpu/drm/bridge/dw_hdmi.c
> @@ -18,6 +18,7 @@
> #include <linux/hdmi.h>
> #include <linux/mutex.h>
> #include <linux/of_device.h>
> +#include <linux/spinlock.h>
>
> #include <drm/drm_of.h>
> #include <drm/drmP.h>
> @@ -124,8 +125,12 @@ struct dw_hdmi {
> struct i2c_adapter *ddc;
> void __iomem *regs;
>
> + spinlock_t audio_lock;
> struct mutex audio_mutex;
> unsigned int sample_rate;
> + unsigned int audio_cts;
> + unsigned int audio_n;
> + bool audio_enable;
> int ratio;
>
> void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
> @@ -347,7 +352,11 @@ static void hdmi_set_clk_regenerator(struct dw_hdmi
> *hdmi,
> dev_dbg(hdmi->dev, "%s: samplerate=%ukHz ratio=%d pixelclk=%luMHz N=%d
> cts=%d\n",
> __func__, sample_rate, ratio, pixel_clk, n, cts);
>
> - hdmi_set_cts_n(hdmi, cts, n);
> + spin_lock_irq(&hdmi->audio_lock);
> + hdmi->audio_n = n;
> + hdmi->audio_cts = cts;
> + hdmi_set_cts_n(hdmi, cts, hdmi->audio_enable ? n : 0);
> + spin_unlock_irq(&hdmi->audio_lock);
> }
>
> static void hdmi_init_clk_regenerator(struct dw_hdmi *hdmi)
> @@ -376,6 +385,28 @@ void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi,
> unsigned int rate)
> }
> EXPORT_SYMBOL_GPL(dw_hdmi_set_sample_rate);
>
> +void dw_hdmi_audio_enable(struct dw_hdmi *hdmi)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&hdmi->audio_lock, flags);
> + hdmi->audio_enable = true;
> + hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
> + spin_unlock_irqrestore(&hdmi->audio_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(dw_hdmi_audio_enable);
> +
> +void dw_hdmi_audio_disable(struct dw_hdmi *hdmi)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&hdmi->audio_lock, flags);
> + hdmi->audio_enable = false;
> + hdmi_set_cts_n(hdmi, hdmi->audio_cts, 0);
> + spin_unlock_irqrestore(&hdmi->audio_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(dw_hdmi_audio_disable);
> +
It is an smart way to operate audio status that do not relate to the audio
interfaces (AHB or I2S), but I am not sure whether this will work on
rockchip
platform, I will do some experiment to test it as soon as possible :)
Best regards.
Yakir Yang
> /*
> * this submodule is responsible for the video data synchronization.
> * for example, for RGB 4:4:4 input, the data map is defined as
> @@ -1579,6 +1610,7 @@ int dw_hdmi_bind(struct device *dev, struct device
> *master,
> hdmi->encoder = encoder;
>
> mutex_init(&hdmi->audio_mutex);
> + spin_lock_init(&hdmi->audio_lock);
>
> of_property_read_u32(np, "reg-io-width", &val);
>
> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
> index 424b51f6a215..ab5d36e83ea2 100644
> --- a/include/drm/bridge/dw_hdmi.h
> +++ b/include/drm/bridge/dw_hdmi.h
> @@ -62,5 +62,7 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
> const struct dw_hdmi_plat_data *plat_data);
>
> void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate);
> +void dw_hdmi_audio_enable(struct dw_hdmi *hdmi);
> +void dw_hdmi_audio_disable(struct dw_hdmi *hdmi);
>
> #endif /* __IMX_HDMI_H__ */
