linux-kernel - [PATCH] clk: qcom: smd-rpm: conditionally enable scaling before doing handover

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Message-Id: <20230506-rpmcc-scaling-handover-v1-1-374338a8dfd9@z3ntu.xyz>
Date:   Sat, 06 May 2023 22:10:32 +0200
From:   Luca Weiss <luca@...tu.xyz>
To:     ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Luca Weiss <luca@...tu.xyz>
Subject: [PATCH] clk: qcom: smd-rpm: conditionally enable scaling before
 doing handover

On older platforms like msm8226, msm8974 and msm8916 the driver in the
downstream kernel enables scaling first before doing the handover of the
clocks.

While this normally doesn't seem to cause noticeable problems, on
apq8026-asus-sparrow this causes the device to immediately reboot,
perhaps due to older rpm firmware that becomes unhappy.

On newer platforms the order has swapped and enabling scaling is done
after the handover, so let's introduce this behavior only conditionally
for msm8226 and msm8974 for now.

Signed-off-by: Luca Weiss <luca@...tu.xyz>
---
 drivers/clk/qcom/clk-smd-rpm.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/qcom/clk-smd-rpm.c b/drivers/clk/qcom/clk-smd-rpm.c
index 887b945a6fb7..6d5476afc4d1 100644
--- a/drivers/clk/qcom/clk-smd-rpm.c
+++ b/drivers/clk/qcom/clk-smd-rpm.c
@@ -178,6 +178,7 @@ struct clk_smd_rpm_req {
 struct rpm_smd_clk_desc {
 	struct clk_smd_rpm **clks;
 	size_t num_clks;
+	bool scaling_before_handover;
 };
 
 static DEFINE_MUTEX(rpm_smd_clk_lock);
@@ -693,6 +694,7 @@ static struct clk_smd_rpm *msm8974_clks[] = {
 static const struct rpm_smd_clk_desc rpm_clk_msm8974 = {
 	.clks = msm8974_clks,
 	.num_clks = ARRAY_SIZE(msm8974_clks),
+	.scaling_before_handover = true,
 };
 
 static struct clk_smd_rpm *msm8976_clks[] = {
@@ -1318,6 +1320,12 @@ static int rpm_smd_clk_probe(struct platform_device *pdev)
 	rpm_smd_clks = desc->clks;
 	num_clks = desc->num_clks;
 
+	if (desc->scaling_before_handover) {
+		ret = clk_smd_rpm_enable_scaling(rpm);
+		if (ret)
+			goto err;
+	}
+
 	for (i = 0; i < num_clks; i++) {
 		if (!rpm_smd_clks[i])
 			continue;
@@ -1329,9 +1337,11 @@ static int rpm_smd_clk_probe(struct platform_device *pdev)
 			goto err;
 	}
 
-	ret = clk_smd_rpm_enable_scaling(rpm);
-	if (ret)
-		goto err;
+	if (!desc->scaling_before_handover) {
+		ret = clk_smd_rpm_enable_scaling(rpm);
+		if (ret)
+			goto err;
+	}
 
 	for (i = 0; i < num_clks; i++) {
 		if (!rpm_smd_clks[i])

---
base-commit: dd9e11d6477a52ede9ebe575c83285e79e823889
change-id: 20230506-rpmcc-scaling-handover-a63029ed9d13

Best regards,
-- 
Luca Weiss <luca@...tu.xyz>