linux-kernel - [PATCH v5 1/1] usb:host:xhci support option to disable the xHCI USB2 HW LPM

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Date:   Tue,  8 Aug 2017 11:27:57 +0700
From:   "Thang Q. Nguyen" <tqnguyen@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Thang Nguyen <tqnguyen@....com>, Phong Vo <pvo@....com>,
        Loc Ho <lho@....com>, Tung Nguyen <tunguyen@....com>,
        patches@....com
Subject: [PATCH v5 1/1] usb:host:xhci support option to disable the xHCI USB2 HW LPM

XHCI specification 1.1 does not require xHCI-compliant controllers
to always enable hardware USB2 LPM. However, the current xHCI
driver always enable it when seeing HLC=1.
This patch supports an option for users to control disabling
USB2 Hardware LPM via DT/ACPI attribute.
This option is needed in case user would like to disable this
feature. For example, their xHCI controller has its USB2 HW LPM
broken.

Signed-off-by: Tung Nguyen <tunguyen@....com>
Signed-off-by: Thang Q. Nguyen <tqnguyen@....com>
Acked-by: Rob Herring <robh@...nel.org>
---
Changes since v4:
 - When HW LPM is optionally disabled, explicitly disable HLE, RWE, ...
 - Update codes to work with kernel 4.13-rc4
 - Add Acked-By from Rob Herring <robh@...nel.org>
Changes since v3:
 - Bypass updating LPM parameters when HW LPM is optionally disabled.
Changes since v2:
 - Change code to disable HW LPM as an option for user which
   is set via ACPI/DT.
Changes since v1:
 - Update DT/ACPI attribute and corresponding codes from HLE to LPM to
   be consistent with other attribute names.
---
 Documentation/devicetree/bindings/usb/usb-xhci.txt |    1 +
 drivers/usb/host/xhci-plat.c                       |    3 +++
 drivers/usb/host/xhci.c                            |    2 +-
 drivers/usb/host/xhci.h                            |    1 +
 4 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
index 2d80b60..ae6e484 100644
--- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
+++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
@@ -26,6 +26,7 @@ Required properties:
 
 Optional properties:
   - clocks: reference to a clock
+  - usb2-lpm-disable: indicate if we don't want to enable USB2 HW LPM
   - usb3-lpm-capable: determines if platform is USB3 LPM capable
   - quirk-broken-port-ped: set if the controller has broken port disable mechanism
 
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index c04144b..9028fb5 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -267,6 +267,9 @@ static int xhci_plat_probe(struct platform_device *pdev)
 		goto disable_clk;
 	}
 
+	if (device_property_read_bool(sysdev, "usb2-lpm-disable"))
+		xhci->quirks |= XHCI_HW_LPM_DISABLE;
+
 	if (device_property_read_bool(sysdev, "usb3-lpm-capable"))
 		xhci->quirks |= XHCI_LPM_SUPPORT;
 
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index b2ff1ff..3a8e75f 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4087,7 +4087,7 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
 	xhci_dbg(xhci, "%s port %d USB2 hardware LPM\n",
 			enable ? "enable" : "disable", port_num + 1);
 
-	if (enable) {
+	if (enable && !(xhci->quirks & XHCI_HW_LPM_DISABLE)) {
 		/* Host supports BESL timeout instead of HIRD */
 		if (udev->usb2_hw_lpm_besl_capable) {
 			/* if device doesn't have a preferred BESL value use a
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index e3e9352..5d89c51 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1821,6 +1821,7 @@ struct xhci_hcd {
 #define XHCI_LIMIT_ENDPOINT_INTERVAL_7	(1 << 26)
 #define XHCI_U2_DISABLE_WAKE	(1 << 27)
 #define XHCI_ASMEDIA_MODIFY_FLOWCONTROL	(1 << 28)
+#define XHCI_HW_LPM_DISABLE	(1 << 29)
 
 	unsigned int		num_active_eps;
 	unsigned int		limit_active_eps;
-- 
1.7.1