drm: bridge/dw_hdmi-ahb-audio: add audio driver

Add ALSA based HDMI AHB audio driver for dw_hdmi.  The only buffer
format supported by the hardware is its own special IEC958 based format,
which is not compatible with any ALSA format.  To avoid doing too much
data manipulation within the driver, we support only ALSAs IEC958 LE and
24-bit PCM formats for 2 to 6 channels, which we convert to its hardware
format.

A more desirable solution would be to have this conversion in userspace,
but ALSA does not appear to allow such transformations outside of
libasound itself.

Reviewed-by: Takashi Iwai <[email protected]>
Tested-by: Fabio Estevam <[email protected]>
Signed-off-by: Russell King <[email protected]>

Author: Russell King

drivers/gpu/drm/bridge/Kconfig

@@ -11,6 +11,17 @@ config DRM_DW_HDMI
 	tristate
 	select DRM_KMS_HELPER
 
+config DRM_DW_HDMI_AHB_AUDIO
+	tristate "Synopsis Designware AHB Audio interface"
+	depends on DRM_DW_HDMI && SND
+	select SND_PCM
+	select SND_PCM_IEC958
+	help
+	  Support the AHB Audio interface which is part of the Synopsis
+	  Designware HDMI block.  This is used in conjunction with
+	  the i.MX6 HDMI driver.
+
+
 config DRM_NXP_PTN3460
 	tristate "NXP PTN3460 DP/LVDS bridge"
 	depends on OF

drivers/gpu/drm/bridge/Makefile

@@ -1,5 +1,6 @@
 ccflags-y := -Iinclude/drm
 
 obj-$(CONFIG_DRM_DW_HDMI) += dw_hdmi.o
+obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw_hdmi-ahb-audio.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
 obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o