linux-kernel - [PATCH] ARM: dts: gta04: fix excess dma channel usage

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Message-Id: <20230113211151.2314874-1-andreas@kemnade.info>
Date:   Fri, 13 Jan 2023 22:11:51 +0100
From:   Andreas Kemnade <andreas@...nade.info>
To:     bcousson@...libre.com, tony@...mide.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, aford173@...il.com,
        linux-omap@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Andreas Kemnade <andreas@...nade.info>
Subject: [PATCH] ARM: dts: gta04: fix excess dma channel usage

From: "H. Nikolaus Schaller" <hns@...delico.com>

OMAP processors support 32 channels but there is no check or
inspect this except booting a device and looking at dmesg reports
of not available channels.

Recently some more subsystems with DMA (aes1+2) were added filling
the list of dma channels beyond the limit of 32 (even if other
parameters indicate 96 or 128 channels). This leads to random
subsystem failures i(e.g. mcbsp for audio) after boot or boot
messages that DMA can not be initialized.

Another symptom is that

/sys/kernel/debug/dmaengine/summary

has 32 entries and does not show all required channels.

Fix by disabling unused (on the GTA04 hardware) mcspi1...4.
Each SPI channel allocates 4 DMA channels rapidly filling
the available ones.

Disabling unused SPI modules on the OMAP3 SoC may also save
some energy (has not been checked).

Fixes: c312f066314e ("ARM: dts: omap3: Migrate AES from hwmods to sysc-omap2")
Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
[re-enabled aes2, improved commit subject line]
Signed-off-by: Andreas Kemnade <andreas@...nade.info>
---
 arch/arm/boot/dts/omap3-gta04.dtsi | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm/boot/dts/omap3-gta04.dtsi b/arch/arm/boot/dts/omap3-gta04.dtsi
index 87e0ab1bbe95..e0be0fb23f80 100644
--- a/arch/arm/boot/dts/omap3-gta04.dtsi
+++ b/arch/arm/boot/dts/omap3-gta04.dtsi
@@ -612,6 +612,22 @@ &i2c3 {
 	clock-frequency = <100000>;
 };

+&mcspi1 {
+	status = "disabled";
+};
+
+&mcspi2 {
+	status = "disabled";
+};
+
+&mcspi3 {
+	status = "disabled";
+};
+
+&mcspi4 {
+	status = "disabled";
+};
+
 &usb_otg_hs {
 	interface-type = <0>;
 	usb-phy = <&usb2_phy>;
-- 
2.30.2