[RFC PATCH 15/16] clk: hifiberry-dacpro: add delay on clock prepare/deprepare

[Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>]

Add a delay to make sure the PCM512x codec can detect SCLK presence.

The initial code from the Raspberry tree used msleep(2), which can be
up to 20ms. A delay of 5-10ms seems fine in practice.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
---
 drivers/clk/clk-hifiberry-dacpro.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/clk/clk-hifiberry-dacpro.c b/drivers/clk/clk-hifiberry-dacpro.c
index f1f5af260083..2907b203fcf2 100644
--- a/drivers/clk/clk-hifiberry-dacpro.c
+++ b/drivers/clk/clk-hifiberry-dacpro.c
@@ -9,6 +9,7 @@
 
 #include <linux/clk-provider.h>
 #include <linux/clkdev.h>
+#include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/gpio/machine.h>
 #include <linux/kernel.h>
@@ -145,6 +146,8 @@ static int clk_hifiberry_dacpro_prepare(struct clk_hw *hw)
 	default:
 		return -EINVAL;
 	}
+	/* wait for SCLK update to be detected by PCM512x codec */
+	usleep_range(5000, 10000);
 
 	clk->prepared = 1;
 
@@ -168,6 +171,8 @@ static void clk_hifiberry_dacpro_unprepare(struct clk_hw *hw)
 	default:
 		return;
 	}
+	/* wait for SCLK update to be detected by PCM512x codec */
+	usleep_range(5000, 10000);
 
 	clk->prepared = false;
 }
-- 
2.20.1