linux-kernel - [PATCH v6 2/5] usb: cdns3-ti: run HW init at resume() if HW was reset

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Message-Id: <20241210-s2r-cdns-v6-2-28a17f9715a2@bootlin.com>
Date: Tue, 10 Dec 2024 18:13:36 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: Peter Chen <peter.chen@...nel.org>, Pawel Laszczak <pawell@...ence.com>, 
 Roger Quadros <rogerq@...nel.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Mathias Nyman <mathias.nyman@...el.com>
Cc: Grégory Clement <gregory.clement@...tlin.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, linux-usb@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Théo Lebrun <theo.lebrun@...tlin.com>
Subject: [PATCH v6 2/5] usb: cdns3-ti: run HW init at resume() if HW was
 reset

At runtime_resume(), read the W1 (Wrapper Register 1) register to detect
if an hardware reset occurred. If it did, run the hardware init sequence.

This callback will be called at system-wide resume. Previously, if a
reset occurred during suspend, we would crash. The wrapper config had
not been written, leading to invalid register accesses inside cdns3.

Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
---
 drivers/usb/cdns3/cdns3-ti.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/usb/cdns3/cdns3-ti.c b/drivers/usb/cdns3/cdns3-ti.c
index d704eb39820ad08a8774be7f00aa473c3ff267c0..d35be7db7616ef5e5bed7dbd53b78a094809f7cc 100644
--- a/drivers/usb/cdns3/cdns3-ti.c
+++ b/drivers/usb/cdns3/cdns3-ti.c
@@ -188,6 +188,12 @@ static int cdns_ti_probe(struct platform_device *pdev)
 	data->vbus_divider = device_property_read_bool(dev, "ti,vbus-divider");
 	data->usb2_only = device_property_read_bool(dev, "ti,usb2-only");
 
+	/*
+	 * The call below to pm_runtime_get_sync() MIGHT reset hardware, if it
+	 * detects it as uninitialised. We want to enforce a reset at probe,
+	 * and so do it manually here. This means the first runtime_resume()
+	 * will be a no-op.
+	 */
 	cdns_ti_reset_and_init_hw(data);
 
 	pm_runtime_enable(dev);
@@ -232,6 +238,24 @@ static void cdns_ti_remove(struct platform_device *pdev)
 	platform_set_drvdata(pdev, NULL);
 }
 
+static int cdns_ti_runtime_resume(struct device *dev)
+{
+	const u32 mask = USBSS_W1_PWRUP_RST | USBSS_W1_MODESTRAP_SEL;
+	struct cdns_ti *data = dev_get_drvdata(dev);
+	u32 w1;
+
+	w1 = cdns_ti_readl(data, USBSS_W1);
+	if ((w1 & mask) != mask)
+		cdns_ti_reset_and_init_hw(data);
+
+	return 0;
+}
+
+static const struct dev_pm_ops cdns_ti_pm_ops = {
+	RUNTIME_PM_OPS(NULL, cdns_ti_runtime_resume, NULL)
+	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+};
+
 static const struct of_device_id cdns_ti_of_match[] = {
 	{ .compatible = "ti,j721e-usb", },
 	{ .compatible = "ti,am64-usb", },
@@ -245,6 +269,7 @@ static struct platform_driver cdns_ti_driver = {
 	.driver		= {
 		.name	= "cdns3-ti",
 		.of_match_table	= cdns_ti_of_match,
+		.pm     = pm_ptr(&cdns_ti_pm_ops),
 	},
 };
 

-- 
2.47.1