linux-kernel - [RFC v2 3/5] arm64: dts: imx8mq: Combine PCIE power domains

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Date:   Thu,  7 Feb 2019 16:29:39 -0800
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     Andrey Smirnov <andrew.smirnov@...il.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Chris Healy <cphealy@...il.com>,
        Leonard Crestez <leonard.crestez@....com>,
        "A.s. Dong" <aisheng.dong@....com>,
        Richard Zhu <hongxing.zhu@....com>, linux-imx@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RFC v2 3/5] arm64: dts: imx8mq: Combine PCIE power domains

According to NXP's FAE feedback and a comment in ATF firmware, PCIE1
and PCIE2 power domains can't really be used independently. Due to
shared reset line both power domains have to be turned on at the same
time. Account for that quirk by combining PCIE power domains into a
single 'pgc_pcie' power domain.

Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
Cc: Shawn Guo <shawnguo@...nel.org>
Cc: Fabio Estevam <fabio.estevam@....com>
Cc: Chris Healy <cphealy@...il.com>
Cc: Lucas Stach <l.stach@...gutronix.de>
Cc: Leonard Crestez <leonard.crestez@....com>
Cc: "A.s. Dong" <aisheng.dong@....com>
Cc: Richard Zhu <hongxing.zhu@....com>
Cc: linux-imx@....com
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
---
 arch/arm64/boot/dts/freescale/imx8mq.dtsi | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mq.dtsi b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
index 50436bd393ed..89babc531380 100644
--- a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
@@ -273,9 +273,28 @@
 						reg = <IMX8M_POWER_DOMAIN_MIPI>;
 					};
 
-					pgc_pcie1: power-domain@1 {
+					/*
+					 * As per comment in ATF source code:
+					 *
+					 * PCIE1 and PCIE2 share the
+					 * same reset signal, if we
+					 * power down PCIE2, PCIE1
+					 * will be held in reset too.
+					 *
+					 * So instead of creating two
+					 * separate power domains for
+					 * PCIE1 and PCIE2. We create
+					 * a link between 1 and 10 and
+					 * use what was supposed to be
+					 * domain 1 as a shared PCIE
+					 * power domain powering both
+					 * PCIE1 and PCIE2 at the same
+					 * time
+					 */
+					pgc_pcie: power-domain@1 {
 						#power-domain-cells = <0>;
 						reg = <IMX8M_POWER_DOMAIN_PCIE1>;
+						power-domains = <&pgc_pcie2>;
 					};
 
 					pgc_otg1: power-domain@2 {
-- 
2.20.1