[PATCH 1/2] clk: qcom: add API to safely park RCG2 sources

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

Some of RCG2 clocks can become stuck during the boot process, when
device drivers are enabling and disabling the RCG2's parent clocks.
To prevernt such outcome of driver probe sequences, add API to park
clocks to the safe clock source (typically TCXO).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/clk/qcom/clk-rcg.h  |  2 ++
 drivers/clk/qcom/clk-rcg2.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/drivers/clk/qcom/clk-rcg.h b/drivers/clk/qcom/clk-rcg.h
index 99efcc7f8d88..9708b8799b01 100644
--- a/drivers/clk/qcom/clk-rcg.h
+++ b/drivers/clk/qcom/clk-rcg.h
@@ -172,6 +172,8 @@ extern const struct clk_ops clk_gfx3d_ops;
 extern const struct clk_ops clk_rcg2_shared_ops;
 extern const struct clk_ops clk_dp_ops;
 
+int clk_rcg2_park_safely(struct regmap *regmap, u32 offset, unsigned int safe_src);
+
 struct clk_rcg_dfs_data {
 	struct clk_rcg2 *rcg;
 	struct clk_init_data *init;
diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
index e1b1b426fae4..230b04a7427c 100644
--- a/drivers/clk/qcom/clk-rcg2.c
+++ b/drivers/clk/qcom/clk-rcg2.c
@@ -1036,6 +1036,40 @@ static void clk_rcg2_shared_disable(struct clk_hw *hw)
 	regmap_write(rcg->clkr.regmap, rcg->cmd_rcgr + CFG_REG, cfg);
 }
 
+int clk_rcg2_park_safely(struct regmap *regmap, u32 offset, unsigned int safe_src)
+{
+	unsigned int val, ret, count;
+
+	ret = regmap_read(regmap, offset + CFG_REG, &val);
+	if (ret)
+		return ret;
+
+	/* assume safe source is 0 */
+	if ((val & CFG_SRC_SEL_MASK) == (safe_src << CFG_SRC_SEL_SHIFT))
+		return 0;
+
+	regmap_write(regmap, offset + CFG_REG, safe_src << CFG_SRC_SEL_SHIFT);
+
+	ret = regmap_update_bits(regmap, offset + CMD_REG,
+				 CMD_UPDATE, CMD_UPDATE);
+	if (ret)
+		return ret;
+
+	/* Wait for update to take effect */
+	for (count = 500; count > 0; count--) {
+		ret = regmap_read(regmap, offset + CMD_REG, &val);
+		if (ret)
+			return ret;
+		if (!(val & CMD_UPDATE))
+			return 0;
+		udelay(1);
+	}
+
+	WARN(1, "the rcg didn't update its configuration.");
+	return -EBUSY;
+}
+EXPORT_SYMBOL_GPL(clk_rcg2_park_safely);
+
 const struct clk_ops clk_rcg2_shared_ops = {
 	.enable = clk_rcg2_shared_enable,
 	.disable = clk_rcg2_shared_disable,
-- 
2.33.0