ASoC: SOF: Intel: cnl-ipc: re-enable IPC IRQ at end of handler

Align with Skylake driver and enable the IRQ at end of handler,
instead of at beginning.

Also add an error log if we have nothing to do in this handler.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/cnl.c

@@ -37,7 +37,7 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 	u32 hipctdd;
 	u32 msg;
 	u32 msg_ext;
-	irqreturn_t ret = IRQ_NONE;
+	bool ipc_irq = false;
 
 	hipcida = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCIDA);
 	hipcctl = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCCTL);
@@ -45,10 +45,6 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 	hipctdd = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCTDD);
 	hipci = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCIDR);
 
-	/* reenable IPC interrupt */
-	snd_sof_dsp_update_bits(sdev, HDA_DSP_BAR, HDA_DSP_REG_ADSPIC,
-				HDA_DSP_ADSPIC_IPC, HDA_DSP_ADSPIC_IPC);
-
 	/* reply message from DSP */
 	if (hipcida & CNL_DSP_REG_HIPCIDA_DONE &&
 	    hipcctl & CNL_DSP_REG_HIPCCTL_DONE) {
@@ -79,7 +75,7 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 
 		spin_unlock_irq(&sdev->ipc_lock);
 
-		ret = IRQ_HANDLED;
+		ipc_irq = true;
 	}
 
 	/* new message from DSP */
@@ -101,10 +97,22 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 
 		cnl_ipc_host_done(sdev);
 
-		ret = IRQ_HANDLED;
+		ipc_irq = true;
+	}
+
+	if (!ipc_irq) {
+		/*
+		 * This interrupt is not shared so no need to return IRQ_NONE.
+		 */
+		dev_err_ratelimited(sdev->dev,
+				    "error: nothing to do in IRQ thread\n");
 	}
 
-	return ret;
+	/* re-enable IPC interrupt */
+	snd_sof_dsp_update_bits(sdev, HDA_DSP_BAR, HDA_DSP_REG_ADSPIC,
+				HDA_DSP_ADSPIC_IPC, HDA_DSP_ADSPIC_IPC);
+
+	return IRQ_HANDLED;
 }
 
 static void cnl_ipc_host_done(struct snd_sof_dev *sdev)