ALSA: ASoC: cs4271: add optional soft reset workaround

The CS4271 requires its LRCLK and MCLK to be stable before its RESET
line is de-asserted. That also means that clocks cannot be changed
without putting the chip back into hardware reset, which also requires
a complete re-initialization of all registers.

One (undocumented) workaround is to assert and de-assert the PDN bit
in the MODE2 register.

This patch adds a new flag to both the DT bindings as well as to the
platform data to enable that workaround.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Alexander Sverdlin <subaparts@yandex.ru>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/sound/cs4271.h b/include/sound/cs4271.h
index dd8c48d14ed9..70f45355acaa 100644
--- a/include/sound/cs4271.h
+++ b/include/sound/cs4271.h
@@ -20,6 +20,21 @@
 struct cs4271_platform_data {
         int gpio_nreset;        /* GPIO driving Reset pin, if any */
         bool amutec_eq_bmutec;  /* flag to enable AMUTEC=BMUTEC */
+
+        /*
+         * The CS4271 requires its LRCLK and MCLK to be stable before its RESET
+         * line is de-asserted. That also means that clocks cannot be changed
+         * without putting the chip back into hardware reset, which also requires
+         * a complete re-initialization of all registers.
+         *
+         * One (undocumented) workaround is to assert and de-assert the PDN bit
+         * in the MODE2 register. This workaround can be enabled with the
+         * following flag.
+         *
+         * Note that this is not needed in case the clocks are stable
+         * throughout the entire runtime of the codec.
+         */
+        bool enable_soft_reset;
 };
 
 #endif /* __CS4271_H */