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Subject[PATCH v2 4/5] USB: dwc2: Don't turn off the usbphy in suspend if wakeup is enabled
Date
If the 'snps,need-phy-for-wake' is set in the device tree then:

- We know that we can wakeup, so call device_set_wakeup_capable().
The USB core will use this knowledge to enable wakeup by default.
- We know that we should keep the PHY on during suspend if something
on our root hub needs remote wakeup. This requires the patch (USB:
Export usb_wakeup_enabled_descendants()). Note that we don't keep
the PHY on at suspend time if it's not needed because it would be a
power draw.

If we later find some users of dwc2 that can support wakeup without
keeping the PHY on we may want to add a way to call
device_set_wakeup_capable() without keeping the PHY on at suspend
time.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
---
For relevant prior discussion of this idea, see:

https://lkml.kernel.org/r/1436207224-21849-4-git-send-email-dianders@chromium.org

If I'm reading all the responses correctly folks were of the opinion
that this patch is still the right way to go.

Changes in v2:
- Rebased to mainline atop rk3288 remote wake quirk series.

drivers/usb/dwc2/core.h | 5 +++++
drivers/usb/dwc2/platform.c | 43 +++++++++++++++++++++++++++++++++++--
2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
index f30748f4fe7e..a99fe7851352 100644
--- a/drivers/usb/dwc2/core.h
+++ b/drivers/usb/dwc2/core.h
@@ -861,6 +861,9 @@ struct dwc2_hregs_backup {
* @hibernated: True if core is hibernated
* @reset_phy_on_wake: Quirk saying that we should assert PHY reset on a
* remote wakeup.
+ * @phy_off_for_suspend: Status of whether we turned the PHY off at suspend.
+ * @need_phy_for_wake: Quirk saying that we should keep the PHY on at
+ * suspend if we need USB to wake us up.
* @frame_number: Frame number read from the core. For both device
* and host modes. The value ranges are from 0
* to HFNUM_MAX_FRNUM.
@@ -1049,6 +1052,8 @@ struct dwc2_hsotg {
unsigned int ll_hw_enabled:1;
unsigned int hibernated:1;
unsigned int reset_phy_on_wake:1;
+ unsigned int need_phy_for_wake:1;
+ unsigned int phy_off_for_suspend:1;
u16 frame_number;

struct phy *phy;
diff --git a/drivers/usb/dwc2/platform.c b/drivers/usb/dwc2/platform.c
index 9b65b766e0b9..6f0271c5d163 100644
--- a/drivers/usb/dwc2/platform.c
+++ b/drivers/usb/dwc2/platform.c
@@ -47,7 +47,9 @@
#include <linux/phy/phy.h>
#include <linux/platform_data/s3c-hsotg.h>
#include <linux/reset.h>
+#include <linux/usb.h>

+#include <linux/usb/hcd.h>
#include <linux/usb/of.h>

#include "core.h"
@@ -450,6 +452,10 @@ static int dwc2_driver_probe(struct platform_device *dev)
if (retval)
goto error;

+ hsotg->need_phy_for_wake =
+ of_property_read_bool(dev->dev.of_node,
+ "snps,need-phy-for-wake");
+
/*
* Reset before dwc2_get_hwparams() then it could get power-on real
* reset value form registers.
@@ -481,6 +487,14 @@ static int dwc2_driver_probe(struct platform_device *dev)
hsotg->gadget_enabled = 1;
}

+ /*
+ * If we need PHY for wakeup we must be wakeup capable.
+ * When we have a device that can wake without the PHY we
+ * can adjust this condition.
+ */
+ if (hsotg->need_phy_for_wake)
+ device_set_wakeup_capable(&dev->dev, true);
+
hsotg->reset_phy_on_wake =
of_property_read_bool(dev->dev.of_node,
"snps,reset-phy-on-wake");
@@ -516,6 +530,28 @@ static int dwc2_driver_probe(struct platform_device *dev)
return retval;
}

+static bool __maybe_unused dwc2_can_poweroff_phy(struct dwc2_hsotg *dwc2)
+{
+ struct usb_device *root_hub = dwc2_hsotg_to_hcd(dwc2)->self.root_hub;
+
+ if (!dwc2->ll_hw_enabled)
+ return false;
+
+ /* If the controller isn't allowed to wakeup then we can power off. */
+ if (!device_may_wakeup(dwc2->dev))
+ return true;
+
+ /*
+ * We don't want to power off the PHY if something under the
+ * root hub has wakeup enabled.
+ */
+ if (usb_wakeup_enabled_descendants(root_hub))
+ return false;
+
+ /* No reason to keep the PHY powered, so allow poweroff */
+ return true;
+}
+
static int __maybe_unused dwc2_suspend(struct device *dev)
{
struct dwc2_hsotg *dwc2 = dev_get_drvdata(dev);
@@ -524,8 +560,10 @@ static int __maybe_unused dwc2_suspend(struct device *dev)
if (dwc2_is_device_mode(dwc2))
dwc2_hsotg_suspend(dwc2);

- if (dwc2->ll_hw_enabled)
+ if (dwc2_can_poweroff_phy(dwc2)) {
ret = __dwc2_lowlevel_hw_disable(dwc2);
+ dwc2->phy_off_for_suspend = true;
+ }

return ret;
}
@@ -535,11 +573,12 @@ static int __maybe_unused dwc2_resume(struct device *dev)
struct dwc2_hsotg *dwc2 = dev_get_drvdata(dev);
int ret = 0;

- if (dwc2->ll_hw_enabled) {
+ if (dwc2->phy_off_for_suspend && dwc2->ll_hw_enabled) {
ret = __dwc2_lowlevel_hw_enable(dwc2);
if (ret)
return ret;
}
+ dwc2->phy_off_for_suspend = false;

if (dwc2_is_device_mode(dwc2))
ret = dwc2_hsotg_resume(dwc2);
--
2.21.0.593.g511ec345e18-goog
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