[PATCH] ASoC: rsnd: adg: make rsnd_adg_clk_control() idempotent

[John Madieu]

rsnd_adg_clk_control() is asymmetric on the disable path: the clkin
clocks are guarded by clkin_rate[], but the "adg" clock is disabled
unconditionally. If an enable attempt fails (for example a clkin
failing to turn on during resume), the error path correctly rolls
everything back, but rsnd_resume() ignores the return value, so the
following system suspend calls rsnd_adg_clk_disable() again and
underflows the "adg" clock enable count:

  adg_0_clks1 already disabled
  WARNING: drivers/clk/clk.c:1188 clk_core_disable+0xa4/0xac
  Call trace:
   clk_core_disable+0xa4/0xac (P)
   clk_disable+0x30/0x4c
   rsnd_adg_clk_control+0x9c/0x2cc
   rsnd_suspend+0x20/0x74
   device_suspend+0x140/0x3ec
   dpm_suspend+0x168/0x270

Track the enable state explicitly and bail out of redundant
enable/disable calls, mirroring what is already done for the per-SSI
clock prepare state. A failed enable leaves the state as disabled, so
the next suspend becomes a no-op and the next resume retries cleanly.

Fixes: 47899d53f86f ("ASoC: rsnd: adg: Add per-SSI ADG and SSIF supply clock management")
Signed-off-by: John Madieu <john.madieu.xa@xxxxxxxxxxxxxx>
---
 sound/soc/renesas/rcar/adg.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/sound/soc/renesas/rcar/adg.c b/sound/soc/renesas/rcar/adg.c
index 5479cefb6dbe..53efd1be5139 100644
--- a/sound/soc/renesas/rcar/adg.c
+++ b/sound/soc/renesas/rcar/adg.c
@@ -45,6 +45,7 @@ struct rsnd_adg {
 	struct rsnd_mod mod;
 	int clkin_rate[CLKINMAX];
 	bool ssi_clk_prepared;
+	bool clk_enabled;
 	int clkin_size;
 	int clkout_size;
 	u32 ckr;
@@ -463,6 +464,22 @@ int rsnd_adg_clk_control(struct rsnd_priv *priv, int enable)
 	struct clk *clk;
 	int ret = 0, i;
 
+	/*
+	 * rsnd_adg_clk_enable() and rsnd_adg_clk_disable() can be called
+	 * redundantly, for example when system suspend follows a resume
+	 * whose enable failed. Make this function idempotent so that the
+	 * "adg" clock, which has no clkin_rate[] style guard, is never
+	 * disabled twice.
+	 */
+	if (enable) {
+		if (adg->clk_enabled)
+			return 0;
+	} else {
+		if (!adg->clk_enabled)
+			return 0;
+		adg->clk_enabled = false;
+	}
+
 	if (enable) {
 		ret = clk_prepare_enable(adg->adg);
 		if (ret < 0)
@@ -520,12 +537,22 @@ int rsnd_adg_clk_control(struct rsnd_priv *priv, int enable)
 	 * rsnd_adg_clk_enable() might return error (_disable() will not).
 	 * We need to rollback in such case
 	 */
-	if (ret < 0)
+	if (ret < 0) {
+		/*
+		 * Mark as enabled so that the rollback below is not
+		 * short-circuited by the idempotency guard. It clears
+		 * the flag again on its way through.
+		 */
+		adg->clk_enabled = true;
 		rsnd_adg_clk_disable(priv);
+		return ret;
+	}
 
 	/* disable adg */
 	if (!enable)
 		clk_disable_unprepare(adg->adg);
+	else
+		adg->clk_enabled = true;
 
 	return ret;
 }
-- 
2.25.1