linux-kernel - [PATCH] Revert "arm64: dts: qcom: sa8540p-ride: enable pcie2a node"

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Message-ID: <pmodcoakbs25z2a7mlo5gpuz63zluh35vbgb5itn6k5aqhjnny@jvphbpvahtse>
Date:   Fri, 2 Jun 2023 15:33:21 -0400
From:   Lucas Karpinski <lkarpins@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        ahalaney@...hat.com, echanude@...hat.com, bmasney@...hat.com,
        quic_shazhuss@...cinc.com
Subject: [PATCH] Revert "arm64: dts: qcom: sa8540p-ride: enable pcie2a node"

This reverts commit 2eb4cdcd5aba2db83f2111de1242721eeb659f71.

The patch introduced a sporadic error where the Qdrive3 will fail to
boot occasionally due to an rcu preempt stall.
Qualcomm has disabled pcie2a downstream:
https://git.codelinaro.org/clo/la/platform/vendor/qcom-opensource/rh-patch/-/commit/447f2135909683d1385af36f95fae5e1d63a7e2f

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu:     0-....: (1 GPs behind) idle=77fc/1/0x4000000000000004 softirq=841/841 fqs=2476
rcu:     (t=5253 jiffies g=-175 q=2552 ncpus=8)
Call trace:
 __do_softirq
 ____do_softirq
 call_on_irq_stack
 do_softirq_own_stack
 __irq_exit_rcu
 irq_exit_rcu

The issue occurs normally once every 3-4 boot cycles.
There is likely a race condition caused when setting up the two pcie
domains concurrently (pcie2a and pcie3a).

The issue is not present when only pcie2a is enabled or when only pcie3a
is enabled.
A workaround was found that allowed the Qdrive3 to boot with both pcie2a
and pcie3a enabled.
Set the .probe_type to PROBE_FORCE_SYNCHRONOUS and add an msleep() to
the probing function.
This is not a solution, so this patch is disabling pcie2a as it seems
Red Hat are the only ones working on the board,
we're find with disabling the node until a root cause is found. If
anyone has further suggestions for debugging, let me know.

Signed-off-by: Lucas Karpinski <lkarpins@...hat.com>
---
 During debugging:
        - Added additional time for clock/regulator stabilization.
        - Reduced the bandwidth across pcie2a and pcie3a.
        - Replaced the interconnect setup from another driver.
        - The 32-bit/64-bit/config-io space for both pcie2a and pcie3a look to be mapped correctly.
        - Verified interconnects were started successfully.

 arch/arm64/boot/dts/qcom/sa8540p-ride.dts | 44 -----------------------
 1 file changed, 44 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sa8540p-ride.dts b/arch/arm64/boot/dts/qcom/sa8540p-ride.dts
index 24fa449d48a6..d492723ccf7c 100644
--- a/arch/arm64/boot/dts/qcom/sa8540p-ride.dts
+++ b/arch/arm64/boot/dts/qcom/sa8540p-ride.dts
@@ -186,27 +186,6 @@ &i2c18 {
 	status = "okay";
 };
 
-&pcie2a {
-	ranges = <0x01000000 0x0 0x3c200000 0x0 0x3c200000 0x0 0x100000>,
-		 <0x02000000 0x0 0x3c300000 0x0 0x3c300000 0x0 0x1d00000>,
-		 <0x03000000 0x5 0x00000000 0x5 0x00000000 0x1 0x00000000>;
-
-	perst-gpios = <&tlmm 143 GPIO_ACTIVE_LOW>;
-	wake-gpios = <&tlmm 145 GPIO_ACTIVE_HIGH>;
-
-	pinctrl-names = "default";
-	pinctrl-0 = <&pcie2a_default>;
-
-	status = "okay";
-};
-
-&pcie2a_phy {
-	vdda-phy-supply = <&vreg_l11a>;
-	vdda-pll-supply = <&vreg_l3a>;
-
-	status = "okay";
-};
-
 &pcie3a {
 	ranges = <0x01000000 0x0 0x40200000 0x0 0x40200000 0x0 0x100000>,
 		 <0x02000000 0x0 0x40300000 0x0 0x40300000 0x0 0x20000000>,
@@ -356,29 +335,6 @@ i2c18_default: i2c18-default-state {
 		bias-pull-up;
 	};
 
-	pcie2a_default: pcie2a-default-state {
-		perst-pins {
-			pins = "gpio143";
-			function = "gpio";
-			drive-strength = <2>;
-			bias-pull-down;
-		};
-
-		clkreq-pins {
-			pins = "gpio142";
-			function = "pcie2a_clkreq";
-			drive-strength = <2>;
-			bias-pull-up;
-		};
-
-		wake-pins {
-			pins = "gpio145";
-			function = "gpio";
-			drive-strength = <2>;
-			bias-pull-up;
-		};
-	};
-
 	pcie3a_default: pcie3a-default-state {
 		perst-pins {
 			pins = "gpio151";
-- 
2.40.1