linux-kernel - [PATCH/RFC] clk: qcom: rpmh: Block system suspend if XO is enabled

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Date:   Tue, 28 Jun 2022 13:13:40 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        patches@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        Taniya Das <quic_tdas@...cinc.com>,
        Mike Tipton <quic_mdtipton@...cinc.com>
Subject: [PATCH/RFC] clk: qcom: rpmh: Block system suspend if XO is enabled

Tracking down what RPMh resource is blocking XO shutdown in suspend is
hard. Largely because we need external debug tools to dump the RPMh
internal state to figure out what resource is enabled. Instead of doing
that, let's just block system wide suspend in the kernel if the RPMh XO
resource is enabled by something in the kernel. This will help us narrow
down XO shutdown failures to the XO clk, and not something else like an
interconnect or regulator RPMh resource.

I'm sending this as an RFC because it breaks suspend for me on Trogdor
boards. I found out that the XO resource is always enabled on these
devices because the audio driver leaves an audio clk always on. This
means that the XO resource must not be used to determine if XO shutdown
is achievable, or we're leaving power savings on the table.

Cc: Taniya Das <quic_tdas@...cinc.com>
Cc: Mike Tipton <quic_mdtipton@...cinc.com>
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
---

Please don't apply. It will break suspend on Trogdor boards.

 drivers/clk/qcom/clk-rpmh.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/clk/qcom/clk-rpmh.c b/drivers/clk/qcom/clk-rpmh.c
index aed907982344..ba0e0e4b9cf2 100644
--- a/drivers/clk/qcom/clk-rpmh.c
+++ b/drivers/clk/qcom/clk-rpmh.c
@@ -70,6 +70,14 @@ struct clk_rpmh_desc {
 
 static DEFINE_MUTEX(rpmh_clk_lock);
 
+/* XO shutdown will fail if XO is enabled across suspend */
+static int clk_rpmh_suspend(struct device *dev)
+{
+	struct clk_rpmh *xo = dev_get_drvdata(dev);
+
+	return xo && xo->state ? -EBUSY : 0;
+}
+
 #define __DEFINE_CLK_RPMH(_platform, _name, _name_active, _res_name,	\
 			  _res_en_offset, _res_on, _div)		\
 	static struct clk_rpmh _platform##_##_name_active;		\
@@ -690,6 +698,10 @@ static int clk_rpmh_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "failed to register %s\n", name);
 			return ret;
 		}
+
+		/* Stash CXO clk for XO shutdown tracking */
+		if (i == RPMH_CXO_CLK)
+			platform_set_drvdata(pdev, rpmh_clk);
 	}
 
 	/* typecast to silence compiler warning */
@@ -722,9 +734,12 @@ static const struct of_device_id clk_rpmh_match_table[] = {
 };
 MODULE_DEVICE_TABLE(of, clk_rpmh_match_table);
 
+static SIMPLE_DEV_PM_OPS(clk_rpmh_pm_ops, clk_rpmh_suspend, NULL);
+
 static struct platform_driver clk_rpmh_driver = {
 	.probe		= clk_rpmh_probe,
 	.driver		= {
+		.pm	= pm_ptr(&clk_rpmh_pm_ops),
 		.name	= "clk-rpmh",
 		.of_match_table = clk_rpmh_match_table,
 	},

base-commit: f2906aa863381afb0015a9eb7fefad885d4e5a56
-- 
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