remoteproc: Add support for xo clock

Add xo clock support required to boot up Qualcomm ADSP processor.
The ADSP remoteproc driver keeps xo clock enabled until the
driver receives "handover" irq, in order to allow ADSP processor
to vote for xo clock with rpm.
Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/qcom_adsp_pil.c

@@ -15,6 +15,7 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/clk.h>
 #include <linux/firmware.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
@@ -48,6 +49,8 @@ struct qcom_adsp {
 	struct qcom_smem_state *state;
 	unsigned stop_bit;
 
+	struct clk *xo;
+
 	struct regulator *cx_supply;
 
 	struct completion start_done;
@@ -102,10 +105,14 @@ static int adsp_start(struct rproc *rproc)
 	struct qcom_adsp *adsp = (struct qcom_adsp *)rproc->priv;
 	int ret;
 
-	ret = regulator_enable(adsp->cx_supply);
+	ret = clk_prepare_enable(adsp->xo);
 	if (ret)
 		return ret;
 
+	ret = regulator_enable(adsp->cx_supply);
+	if (ret)
+		goto disable_clocks;
+
 	ret = qcom_scm_pas_auth_and_reset(ADSP_PAS_ID);
 	if (ret) {
 		dev_err(adsp->dev,
@@ -126,6 +133,8 @@ static int adsp_start(struct rproc *rproc)
 
 disable_regulators:
 	regulator_disable(adsp->cx_supply);
+disable_clocks:
+	clk_disable_unprepare(adsp->xo);
 
 	return ret;
 }
@@ -223,6 +232,21 @@ static irqreturn_t adsp_stop_ack_interrupt(int irq, void *dev)
 	return IRQ_HANDLED;
 }
 
+static int adsp_init_clock(struct qcom_adsp *adsp)
+{
+	int ret;
+
+	adsp->xo = devm_clk_get(adsp->dev, "xo");
+	if (IS_ERR(adsp->xo)) {
+		ret = PTR_ERR(adsp->xo);
+		if (ret != -EPROBE_DEFER)
+			dev_err(adsp->dev, "failed to get xo clock");
+		return ret;
+	}
+
+	return 0;
+}
+
 static int adsp_init_regulator(struct qcom_adsp *adsp)
 {
 	adsp->cx_supply = devm_regulator_get(adsp->dev, "cx");
@@ -320,6 +344,10 @@ static int adsp_probe(struct platform_device *pdev)
 	if (ret)
 		goto free_rproc;
 
+	ret = adsp_init_clock(adsp);
+	if (ret)
+		goto free_rproc;
+
 	ret = adsp_init_regulator(adsp);
 	if (ret)
 		goto free_rproc;