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* [PATCH] clk: qcom: clk-alpha-pll: Don't reconfigure running Trion
@ 2021-11-23 16:16 Bjorn Andersson
  2021-11-23 16:25 ` [PATCH v2] " Bjorn Andersson
                   ` (2 more replies)
  0 siblings, 3 replies; 7+ messages in thread
From: Bjorn Andersson @ 2021-11-23 16:16 UTC (permalink / raw)
  To: Michael Turquette, Stephen Boyd, Taniya Das, Vinod Koul
  Cc: linux-arm-msm, linux-clk, linux-kernel

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>
---
 drivers/clk/qcom/clk-alpha-pll.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
index eaedcceb766f..b04aa0a630e9 100644
--- 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_dbg("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);
-- 
2.33.1


^ permalink raw reply related	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2021-12-03  0:59 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-11-23 16:16 [PATCH] clk: qcom: clk-alpha-pll: Don't reconfigure running Trion Bjorn Andersson
2021-11-23 16:25 ` [PATCH v2] " Bjorn Andersson
2021-11-23 17:02   ` Robert Foss
2021-11-24  4:23   ` Vinod Koul
2021-12-03  0:59   ` Stephen Boyd
2021-11-24  1:45 ` [PATCH] " kernel test robot
2021-11-24 10:46 ` kernel test robot

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