clk: qcom: clk-alpha-pll: Don't reconfigure running Trion

commit a1f0019c342bd83240b05be68c9888549dde7935 upstream.

In the event that the bootloader has configured the Trion PLL as source
for the display clocks, e.g. for the continuous splashscreen, then there
will also be RCGs that are clocked by this instance.

Reconfiguring, and in particular disabling the output of, the PLL will
cause issues for these downstream RCGs and has been shown to prevent
them from being re-parented.

Follow downstream and skip configuration if it's determined that the PLL
is already running.

Fixes: 59128c20a6a9 ("clk: qcom: clk-alpha-pll: Add support for controlling Lucid PLLs")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20211123162508.153711-1-bjorn.andersson@linaro.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
index eaedcceb766f91e9ba9ad5d61b23088f15cacaf5..8f65b9bdafce4f38dc2c58f681bd1e8c6d92de8f 100644 (file)
--- a/drivers/clk/qcom/clk-alpha-pll.c
+++ b/drivers/clk/qcom/clk-alpha-pll.c
@@ -1429,6 +1429,15 @@ EXPORT_SYMBOL_GPL(clk_alpha_pll_postdiv_fabia_ops);
 void clk_trion_pll_configure(struct clk_alpha_pll *pll, struct regmap *regmap,
                             const struct alpha_pll_config *config)
 {
+       /*
+        * If the bootloader left the PLL enabled it's likely that there are
+        * RCGs that will lock up if we disable the PLL below.
+        */
+       if (trion_pll_is_enabled(pll, regmap)) {
+               pr_debug("Trion PLL is already enabled, skipping configuration\n");
+               return;
+       }
+
        clk_alpha_pll_write_config(regmap, PLL_L_VAL(pll), config->l);
        regmap_write(regmap, PLL_CAL_L_VAL(pll), TRION_PLL_CAL_VAL);
        clk_alpha_pll_write_config(regmap, PLL_ALPHA_VAL(pll), config->alpha);