[PATCH v3 11/12] usb: dwc3: qcom: Transition to flattened model

Bjorn Andersson
2025-01-14T05:06:14Z

The USB IP-block found in most Qualcomm platforms is modelled in the
Linux kernel as 3 different independent device drivers, but as shown by
the already existing layering violations in the Qualcomm glue driver
they can not be operated independently.

With the current implementation, the glue driver registers the core and
has no way to know when this is done. As a result, e.g. the suspend
callbacks needs to guard against NULL pointer dereferences when trying
to peek into the struct dwc3 found in the drvdata of the child.
Even with these checks, there are no way to fully protect ourselves from
the race conditions that occur if the DWC3 is unbound.

Missing from the upstream Qualcomm USB support is handling of role
switching, in which the glue needs to be notified upon DRD mode changes.
Several attempts has been made through the years to register callbacks
etc, but they always fall short when it comes to handling of the core's
probe deferral on resources etc.

Moving to a model where the DWC3 core is instantiated in a synchronous
fashion avoids above described race conditions.

It is however not feasible to do so without also flattening the
DeviceTree binding, as assumptions are made in the DWC3 core and
frameworks used that the device's associated of_node will the that of
the core. Furthermore, the DeviceTree binding is a direct
representation of the Linux driver model, and doesn't necessarily
describe "the USB IP-block".

The Qualcomm DWC3 glue driver is therefor transitioned to initialize and
operate the DWC3 within the one device context, in synchronous fashion.

To handle backwards compatibility, and to remove the two-device model,
of_nodes of the old compatible are converted to the new one, early
during probe.

This happens in the event that a DWC3 core child node is present, the
content of the reg and interrupt properties of this node are merged into
the shared properties, all remaining properties are copied and the core
node is dropped. Effectively transitioning the node from qcom,dwc3 to
qcom,snps-dwc3.

As the dwc3-qcom driver is migrated to support (and only support) the
qcom,snps-dwc3 binding, the kill-switch in the dwc3-flattening overlay
code is removed.

Signed-off-by: Bjorn Andersson <bjorn.andersson@oss.qualcomm.com>
---
.../of/overlays/dwc3-flattening/dwc3-flattening.c | 3 -
drivers/usb/dwc3/dwc3-qcom.c | 136 ++++++++++-----------
2 files changed, 66 insertions(+), 73 deletions(-)

diff --git a/drivers/of/overlays/dwc3-flattening/dwc3-flattening.c b/drivers/of/overlays/dwc3-flattening/dwc3-flattening.c
index 07f90360c04d..44bc97ac53c0 100644
--- a/drivers/of/overlays/dwc3-flattening/dwc3-flattening.c
+++ b/drivers/of/overlays/dwc3-flattening/dwc3-flattening.c
@@ -1500,9 +1500,6 @@ static int dwc3_flattening_init(void)
int overlay_ovcs;
int ret;

- /* TODO: Remove kill-switch as dwc3-qcom is migrated to qcom,snps-dwc */
- return 0;
-
match = of_match_node(dwc3_flatten_of_match, of_root);
if (!match)
return 0;
diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index 50b1da845113..df1ee6961c9e 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -14,7 +14,8 @@
#include <linux/kernel.h>
#include <linux/extcon.h>
#include <linux/interconnect.h>
-#include <linux/of_platform.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/phy/phy.h>
#include <linux/usb/of.h>
@@ -23,6 +24,7 @@
#include <linux/usb/hcd.h>
#include <linux/usb.h>
#include "core.h"
+#include "glue.h"

/* USB QSCRATCH Hardware registers */
#define QSCRATCH_HS_PHY_CTRL 0x10
@@ -73,7 +75,7 @@ struct dwc3_qcom_port {
struct dwc3_qcom {
struct device *dev;
void __iomem *qscratch_base;
- struct platform_device *dwc3;
+ struct dwc3 dwc;
struct clk **clks;
int num_clocks;
struct reset_control *resets;
@@ -92,6 +94,8 @@ struct dwc3_qcom {
struct icc_path *icc_path_apps;
};

+#define to_dwc3_qcom(d) container_of((d), struct dwc3_qcom, dwc)
+
static inline void dwc3_qcom_setbits(void __iomem *base, u32 offset, u32 val)
{
u32 reg;
@@ -260,7 +264,7 @@ static int dwc3_qcom_interconnect_init(struct dwc3_qcom *qcom)
goto put_path_ddr;
}

- max_speed = usb_get_maximum_speed(&qcom->dwc3->dev);
+ max_speed = usb_get_maximum_speed(qcom->dwc.dev);
if (max_speed >= USB_SPEED_SUPER || max_speed == USB_SPEED_UNKNOWN) {
ret = icc_set_bw(qcom->icc_path_ddr,
USB_MEMORY_AVG_SS_BW, USB_MEMORY_PEAK_SS_BW);
@@ -303,25 +307,14 @@ static void dwc3_qcom_interconnect_exit(struct dwc3_qcom *qcom)
/* Only usable in contexts where the role can not change. */
static bool dwc3_qcom_is_host(struct dwc3_qcom *qcom)
{
- struct dwc3 *dwc;
-
- /*
- * FIXME: Fix this layering violation.
- */
- dwc = platform_get_drvdata(qcom->dwc3);
-
- /* Core driver may not have probed yet. */
- if (!dwc)
- return false;
-
- return dwc->xhci;
+ return qcom->dwc.xhci;
}

static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom, int port_index)
{
- struct dwc3 *dwc = platform_get_drvdata(qcom->dwc3);
struct usb_device *udev;
struct usb_hcd __maybe_unused *hcd;
+ struct dwc3 *dwc = &qcom->dwc;

/*
* FIXME: Fix this layering violation.
@@ -498,7 +491,7 @@ static int dwc3_qcom_resume(struct dwc3_qcom *qcom, bool wakeup)
static irqreturn_t qcom_dwc3_resume_irq(int irq, void *data)
{
struct dwc3_qcom *qcom = data;
- struct dwc3 *dwc = platform_get_drvdata(qcom->dwc3);
+ struct dwc3 *dwc = &qcom->dwc;

/* If pm_suspended then let pm_resume take care of resuming h/w */
if (qcom->pm_suspended)
@@ -700,40 +693,13 @@ static int dwc3_qcom_clk_init(struct dwc3_qcom *qcom, int count)
return 0;
}

-static int dwc3_qcom_of_register_core(struct dwc3_qcom *qcom, struct platform_device *pdev)
-{
- struct device_node *np = pdev->dev.of_node;
- struct device *dev = &pdev->dev;
- int ret;
-
- struct device_node *dwc3_np __free(device_node) = of_get_compatible_child(np,
- "snps,dwc3");
- if (!dwc3_np) {
- dev_err(dev, "failed to find dwc3 core child\n");
- return -ENODEV;
- }
-
- ret = of_platform_populate(np, NULL, NULL, dev);
- if (ret) {
- dev_err(dev, "failed to register dwc3 core - %d\n", ret);
- return ret;
- }
-
- qcom->dwc3 = of_find_device_by_node(dwc3_np);
- if (!qcom->dwc3) {
- ret = -ENODEV;
- dev_err(dev, "failed to get dwc3 platform device\n");
- of_platform_depopulate(dev);
- }
-
- return ret;
-}
-
static int dwc3_qcom_probe(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node;
struct device *dev = &pdev->dev;
struct dwc3_qcom *qcom;
+ struct resource res;
+ struct resource *r;
int ret, i;
bool ignore_pipe_clk;
bool wakeup_source;
@@ -742,7 +708,6 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
if (!qcom)
return -ENOMEM;

- platform_set_drvdata(pdev, qcom);
qcom->dev = &pdev->dev;

qcom->resets = devm_reset_control_array_get_optional_exclusive(dev);
@@ -771,8 +736,15 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
goto reset_assert;
}

- qcom->qscratch_base = devm_platform_ioremap_resource(pdev, 0);
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!r)
+ goto clk_disable;
+ res = *r;
+ res.end = res.start + SDM845_QSCRATCH_BASE_OFFSET;
+
+ qcom->qscratch_base = devm_ioremap(dev, res.end, SDM845_QSCRATCH_SIZE);
if (IS_ERR(qcom->qscratch_base)) {
+ dev_err(dev, "failed to map qscratch region: %pe\n", qcom->qscratch_base);
ret = PTR_ERR(qcom->qscratch_base);
goto clk_disable;
}
@@ -792,17 +764,18 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
if (ignore_pipe_clk)
dwc3_qcom_select_utmi_clk(qcom);

- ret = dwc3_qcom_of_register_core(qcom, pdev);
- if (ret) {
- dev_err(dev, "failed to register DWC3 Core, err=%d\n", ret);
+ qcom->dwc.dev = dev;
+ ret = dwc3_init(&qcom->dwc, &res, true);
+ if (ret) {
+ ret = dev_err_probe(dev, ret, "failed to register DWC3 Core\n");
goto clk_disable;
}

ret = dwc3_qcom_interconnect_init(qcom);
if (ret)
- goto depopulate;
+ goto remove_core;

- qcom->mode = usb_get_dr_mode(&qcom->dwc3->dev);
+ qcom->mode = usb_get_dr_mode(dev);

/* enable vbus override for device mode */
if (qcom->mode != USB_DR_MODE_HOST)
@@ -815,20 +788,15 @@ static int dwc3_qcom_probe(struct platform_device *pdev)

wakeup_source = of_property_read_bool(dev->of_node, "wakeup-source");
device_init_wakeup(&pdev->dev, wakeup_source);
- device_init_wakeup(&qcom->dwc3->dev, wakeup_source);

qcom->is_suspended = false;
- pm_runtime_set_active(dev);
- pm_runtime_enable(dev);
- pm_runtime_forbid(dev);

return 0;

interconnect_exit:
dwc3_qcom_interconnect_exit(qcom);
-depopulate:
- of_platform_depopulate(&pdev->dev);
- platform_device_put(qcom->dwc3);
+remove_core:
+ dwc3_uninit(&qcom->dwc);
clk_disable:
for (i = qcom->num_clocks - 1; i >= 0; i--) {
clk_disable_unprepare(qcom->clks[i]);
@@ -842,13 +810,11 @@ static int dwc3_qcom_probe(struct platform_device *pdev)

static void dwc3_qcom_remove(struct platform_device *pdev)
{
- struct dwc3_qcom *qcom = platform_get_drvdata(pdev);
+ struct dwc3 *dwc = platform_get_drvdata(pdev);
+ struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
struct device *dev = &pdev->dev;
int i;

- of_platform_depopulate(&pdev->dev);
- platform_device_put(qcom->dwc3);
-
for (i = qcom->num_clocks - 1; i >= 0; i--) {
clk_disable_unprepare(qcom->clks[i]);
clk_put(qcom->clks[i]);
@@ -864,10 +830,15 @@ static void dwc3_qcom_remove(struct platform_device *pdev)

static int __maybe_unused dwc3_qcom_pm_suspend(struct device *dev)
{
- struct dwc3_qcom *qcom = dev_get_drvdata(dev);
+ struct dwc3 *dwc = dev_get_drvdata(dev);
+ struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
bool wakeup = device_may_wakeup(dev);
int ret;

+ ret = dwc3_suspend(&qcom->dwc);
+ if (ret)
+ return ret;
+
ret = dwc3_qcom_suspend(qcom, wakeup);
if (ret)
return ret;
@@ -879,7 +850,8 @@ static int __maybe_unused dwc3_qcom_pm_suspend(struct device *dev)

static int __maybe_unused dwc3_qcom_pm_resume(struct device *dev)
{
- struct dwc3_qcom *qcom = dev_get_drvdata(dev);
+ struct dwc3 *dwc = dev_get_drvdata(dev);
+ struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
bool wakeup = device_may_wakeup(dev);
int ret;

@@ -889,31 +861,55 @@ static int __maybe_unused dwc3_qcom_pm_resume(struct device *dev)

qcom->pm_suspended = false;

+ ret = dwc3_resume(&qcom->dwc);
+ if (ret)
+ return ret;
+
return 0;
}

static int __maybe_unused dwc3_qcom_runtime_suspend(struct device *dev)
{
- struct dwc3_qcom *qcom = dev_get_drvdata(dev);
+ struct dwc3 *dwc = dev_get_drvdata(dev);
+ struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
+ int ret;
+
+ ret = dwc3_runtime_suspend(&qcom->dwc);
+ if (ret)
+ return ret;

return dwc3_qcom_suspend(qcom, true);
}

+static void __maybe_unused dwc3_qcom_complete(struct device *dev)
+{
+ struct dwc3 *dwc = dev_get_drvdata(dev);
+
+ dwc3_complete(dwc);
+}
+
static int __maybe_unused dwc3_qcom_runtime_resume(struct device *dev)
{
- struct dwc3_qcom *qcom = dev_get_drvdata(dev);
+ struct dwc3 *dwc = dev_get_drvdata(dev);
+ struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
+ int ret;
+
+ ret = dwc3_qcom_resume(qcom, true);
+ if (ret)
+ return ret;

- return dwc3_qcom_resume(qcom, true);
+ return dwc3_runtime_resume(&qcom->dwc);
}

static const struct dev_pm_ops dwc3_qcom_dev_pm_ops = {
SET_SYSTEM_SLEEP_PM_OPS(dwc3_qcom_pm_suspend, dwc3_qcom_pm_resume)
SET_RUNTIME_PM_OPS(dwc3_qcom_runtime_suspend, dwc3_qcom_runtime_resume,
NULL)
+ .complete = dwc3_qcom_complete,
};

static const struct of_device_id dwc3_qcom_of_match[] = {
- { .compatible = "qcom,dwc3" },
+ { .compatible = "qcom,snps-dwc3" },
{ }
};
MODULE_DEVICE_TABLE(of, dwc3_qcom_of_match);

--
2.45.2