[PATCH] ASoC: atmel: fix atmel_ssc_set_audio link failure

[Arnd Bergmann <arnd@arndb.de>]

The ssc audio driver can call into both pdc and dma backends.  With the
latest rework, the logic to do this in a safe way avoiding link errors
was removed, bringing back link errors that were fixed long ago in commit
061981ff8cc8 ("ASoC: atmel: properly select dma driver state") such as

sound/soc/atmel/atmel_ssc_dai.o: In function `atmel_ssc_set_audio':
atmel_ssc_dai.c:(.text+0xac): undefined reference to `atmel_pcm_pdc_platform_register'

Fix it this time using Makefile hacks and a comment to prevent this
from accidentally getting removed again rather than Kconfig hacks.

Fixes: 18291410557f ("ASoC: atmel: enable SOC_SSC_PDC and SOC_SSC_DMA in Kconfig")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 sound/soc/atmel/Kconfig  |  4 ++--
 sound/soc/atmel/Makefile | 10 ++++++++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/sound/soc/atmel/Kconfig b/sound/soc/atmel/Kconfig
index f118c229ed82..25c31bf64936 100644
--- a/sound/soc/atmel/Kconfig
+++ b/sound/soc/atmel/Kconfig
@@ -10,11 +10,11 @@ config SND_ATMEL_SOC
 if SND_ATMEL_SOC
 
 config SND_ATMEL_SOC_PDC
-	tristate
+	bool
 	depends on HAS_DMA
 
 config SND_ATMEL_SOC_DMA
-	tristate
+	bool
 	select SND_SOC_GENERIC_DMAENGINE_PCM
 
 config SND_ATMEL_SOC_SSC
diff --git a/sound/soc/atmel/Makefile b/sound/soc/atmel/Makefile
index 1f6890ed3738..c7d2989791be 100644
--- a/sound/soc/atmel/Makefile
+++ b/sound/soc/atmel/Makefile
@@ -6,8 +6,14 @@ snd-soc-atmel_ssc_dai-objs := atmel_ssc_dai.o
 snd-soc-atmel-i2s-objs := atmel-i2s.o
 snd-soc-mchp-i2s-mcc-objs := mchp-i2s-mcc.o
 
-obj-$(CONFIG_SND_ATMEL_SOC_PDC) += snd-soc-atmel-pcm-pdc.o
-obj-$(CONFIG_SND_ATMEL_SOC_DMA) += snd-soc-atmel-pcm-dma.o
+# pdc and dma need to both be built-in if any user of
+# ssc is built-in.
+ifdef CONFIG_SND_ATMEL_SOC_PDC
+obj-$(CONFIG_SND_ATMEL_SOC_SSC) += snd-soc-atmel-pcm-pdc.o
+endif
+ifdef CONFIG_SND_ATMEL_SOC_DMA
+obj-$(CONFIG_SND_ATMEL_SOC_SSC) += snd-soc-atmel-pcm-dma.o
+endif
 obj-$(CONFIG_SND_ATMEL_SOC_SSC) += snd-soc-atmel_ssc_dai.o
 obj-$(CONFIG_SND_ATMEL_SOC_I2S) += snd-soc-atmel-i2s.o
 obj-$(CONFIG_SND_MCHP_SOC_I2S_MCC) += snd-soc-mchp-i2s-mcc.o
-- 
2.20.0