clk: qcom: regmap-mux: add pipe clk implementation

On recent Qualcomm platforms the QMP PIPE clocks feed into a set of
muxes which must be parked to the "safe" source (bi_tcxo) when
corresponding GDSC is turned off and on again. Currently this is
handcoded in the PCIe driver by reparenting the gcc_pipe_N_clk_src
clock. However the same code sequence should be applied in the
pcie-qcom endpoint, USB3 and UFS drivers.

Rather than copying this sequence over and over again, follow the
example of clk_rcg2_shared_ops and implement this parking in the
enable() and disable() clock operations. As we are changing the parent
behind the back of the clock framework, also implement custom
set_parent() and get_parent() operations behaving accroding to the clock
framework expectations (cache the new parent if the clock is in disabled
state, return cached parent).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220323085010.1753493-2-dmitry.baryshkov@linaro.org

drivers/clk/qcom/clk-regmap-mux.c

@@ -49,9 +49,87 @@ static int mux_set_parent(struct clk_hw *hw, u8 index)
 	return regmap_update_bits(clkr->regmap, mux->reg, mask, val);
 }
 
+static u8 mux_safe_get_parent(struct clk_hw *hw)
+{
+	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
+	unsigned int val;
+
+	if (clk_hw_is_enabled(hw))
+		return mux_get_parent(hw);
+
+	val = mux->stored_parent_cfg;
+
+	if (mux->parent_map)
+		return qcom_find_cfg_index(hw, mux->parent_map, val);
+
+	return val;
+}
+
+static int mux_safe_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
+
+	if (clk_hw_is_enabled(hw))
+		return mux_set_parent(hw, index);
+
+	if (mux->parent_map)
+		index = mux->parent_map[index].cfg;
+
+	mux->stored_parent_cfg = index;
+
+	return 0;
+}
+
+static void mux_safe_disable(struct clk_hw *hw)
+{
+	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
+	struct clk_regmap *clkr = to_clk_regmap(hw);
+	unsigned int mask = GENMASK(mux->width + mux->shift - 1, mux->shift);
+	unsigned int val;
+
+	regmap_read(clkr->regmap, mux->reg, &val);
+
+	mux->stored_parent_cfg = (val & mask) >> mux->shift;
+
+	val = mux->safe_src_parent;
+	if (mux->parent_map) {
+		int index = qcom_find_src_index(hw, mux->parent_map, val);
+
+		if (WARN_ON(index < 0))
+			return;
+
+		val = mux->parent_map[index].cfg;
+	}
+	val <<= mux->shift;
+
+	regmap_update_bits(clkr->regmap, mux->reg, mask, val);
+}
+
+static int mux_safe_enable(struct clk_hw *hw)
+{
+	struct clk_regmap_mux *mux = to_clk_regmap_mux(hw);
+	struct clk_regmap *clkr = to_clk_regmap(hw);
+	unsigned int mask = GENMASK(mux->width + mux->shift - 1, mux->shift);
+	unsigned int val;
+
+	val = mux->stored_parent_cfg;
+	val <<= mux->shift;
+
+	return regmap_update_bits(clkr->regmap, mux->reg, mask, val);
+}
+
 const struct clk_ops clk_regmap_mux_closest_ops = {
 	.get_parent = mux_get_parent,
 	.set_parent = mux_set_parent,
 	.determine_rate = __clk_mux_determine_rate_closest,
 };
 EXPORT_SYMBOL_GPL(clk_regmap_mux_closest_ops);
+
+const struct clk_ops clk_regmap_mux_safe_ops = {
+	.enable = mux_safe_enable,
+	.disable = mux_safe_disable,
+	.get_parent = mux_safe_get_parent,
+	.set_parent = mux_safe_set_parent,
+	.determine_rate = __clk_mux_determine_rate_closest,
+};
+EXPORT_SYMBOL_GPL(clk_regmap_mux_safe_ops);

drivers/clk/qcom/clk-regmap-mux.h

@@ -14,10 +14,13 @@ struct clk_regmap_mux {
 	u32			reg;
 	u32			shift;
 	u32			width;
+	u8			safe_src_parent;
+	u8			stored_parent_cfg;
 	const struct parent_map	*parent_map;
 	struct clk_regmap	clkr;
 };
 
 extern const struct clk_ops clk_regmap_mux_closest_ops;
+extern const struct clk_ops clk_regmap_mux_safe_ops;
 
 #endif