Hi Thierry,

Thanks for your review! I'll update in the next patchset.

thanks, Wayne.

On 3/21/25 20:22, Thierry Reding wrote:

On Fri, Mar 14, 2025 at 03:33:48PM +0800, Wayne Chang wrote:

...

The current implementation uses bias_pad_enable as a reference count to manage the shared bias pad for all UTMI PHYs. However, during system suspension with connected USB devices, multiple power-down requests for the UTMI pad result in a mismatch in the reference count, which in turn produces warnings such as:

[ 237.762967] WARNING: CPU: 10 PID: 1618 at tegra186_utmi_pad_power_down+0x160/0x170 [ 237.763103] Call trace: [ 237.763104] tegra186_utmi_pad_power_down+0x160/0x170 [ 237.763107] tegra186_utmi_phy_power_off+0x10/0x30 [ 237.763110] phy_power_off+0x48/0x100 [ 237.763113] tegra_xusb_enter_elpg+0x204/0x500 [ 237.763119] tegra_xusb_suspend+0x48/0x140 [ 237.763122] platform_pm_suspend+0x2c/0xb0 [ 237.763125] dpm_run_callback.isra.0+0x20/0xa0 [ 237.763127] __device_suspend+0x118/0x330 [ 237.763129] dpm_suspend+0x10c/0x1f0 [ 237.763130] dpm_suspend_start+0x88/0xb0 [ 237.763132] suspend_devices_and_enter+0x120/0x500 [ 237.763135] pm_suspend+0x1ec/0x270

The root cause was traced back to the dynamic power-down changes introduced in commit a30951d31b25 ("xhci: tegra: USB2 pad power controls"), where the UTMI pad was being powered down without verifying its current state. This unbalanced behavior led to discrepancies in the reference count.

To rectify this issue, this patch replaces the single reference counter with a bitmask, renamed to utmi_pad_enabled. Each bit in the mask corresponds to one of the four USB2 PHYs, allowing us to track each pad's enablement status individually.

With this change:

• The bias pad is powered on only when the mask is clear.
• Each UTMI pad is powered on or down based on its corresponding bit in the mask, preventing redundant operations.
• The overall power state of the shared bias pad is maintained correctly during suspend/resume cycles.

Cc: stable@vger.kernel.org Fixes: a30951d31b25 ("xhci: tegra: USB2 pad power controls") Signed-off-by: Wayne Chang waynec@nvidia.com

---

drivers/phy/tegra/xusb-tegra186.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/phy/tegra/xusb-tegra186.c b/drivers/phy/tegra/xusb-tegra186.c index fae6242aa730..77bb27a34738 100644 --- a/drivers/phy/tegra/xusb-tegra186.c +++ b/drivers/phy/tegra/xusb-tegra186.c @@ -237,6 +237,8 @@ #define DATA0_VAL_PD BIT(1) #define USE_XUSB_AO BIT(4) +#define TEGRA_UTMI_PAD_MAX 4

• #define TEGRA186_LANE(_name, _offset, _shift, _mask, _type) \ { \ .name = _name, \

@@ -269,7 +271,7 @@ struct tegra186_xusb_padctl { /* UTMI bias and tracking */ struct clk *usb2_trk_clk;

• unsigned int bias_pad_enable;

• DECLARE_BITMAP(utmi_pad_enabled, TEGRA_UTMI_PAD_MAX);

/* padctl context */ struct tegra186_xusb_padctl_context context; @@ -605,7 +607,7 @@ static void tegra186_utmi_bias_pad_power_on(struct tegra_xusb_padctl *padctl) mutex_lock(&padctl->lock);

• if (priv->bias_pad_enable++ > 0) {

• if (!bitmap_empty(priv->utmi_pad_enabled, TEGRA_UTMI_PAD_MAX)) { mutex_unlock(&padctl->lock); return; }

@@ -669,12 +671,7 @@ static void tegra186_utmi_bias_pad_power_off(struct tegra_xusb_padctl *padctl) mutex_lock(&padctl->lock);

• if (WARN_ON(priv->bias_pad_enable == 0)) {

• mutex_unlock(&padctl->lock);
  

• return;
  

• }
• if (--priv->bias_pad_enable > 0) {

• if (!bitmap_empty(priv->utmi_pad_enabled, TEGRA_UTMI_PAD_MAX)) { mutex_unlock(&padctl->lock); return; }

@@ -697,6 +694,7 @@ static void tegra186_utmi_pad_power_on(struct phy *phy) { struct tegra_xusb_lane *lane = phy_get_drvdata(phy); struct tegra_xusb_padctl *padctl = lane->pad->padctl;

• struct tegra186_xusb_padctl *priv = to_tegra186_xusb_padctl(padctl); struct tegra_xusb_usb2_port *port; struct device *dev = padctl->dev; unsigned int index = lane->index;

@@ -705,6 +703,9 @@ static void tegra186_utmi_pad_power_on(struct phy *phy) if (!phy) return;

• if (test_bit(index, priv->utmi_pad_enabled))

• return;
  

Don't we need to take the padctl->lock mutex before this...

...

• port = tegra_xusb_find_usb2_port(padctl, index); if (!port) { dev_err(dev, "no port found for USB2 lane %u\n", index);

@@ -724,18 +725,24 @@ static void tegra186_utmi_pad_power_on(struct phy *phy) value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index)); value &= ~USB2_OTG_PD_DR; padctl_writel(padctl, value, XUSB_PADCTL_USB2_OTG_PADX_CTL1(index));

• set_bit(index, priv->utmi_pad_enabled);

... and release it here? Otherwise we might end up testing, setting and/ or clearing from two pads concurrently and loose consistency.

...

} static void tegra186_utmi_pad_power_down(struct phy *phy) { struct tegra_xusb_lane *lane = phy_get_drvdata(phy); struct tegra_xusb_padctl *padctl = lane->pad->padctl;

• struct tegra186_xusb_padctl *priv = to_tegra186_xusb_padctl(padctl); unsigned int index = lane->index; u32 value;

if (!phy) return;

• if (!test_bit(index, priv->utmi_pad_enabled))

• return;
  

Same here...

...

dev_dbg(padctl->dev, "power down UTMI pad %u\n", index); value = padctl_readl(padctl, XUSB_PADCTL_USB2_OTG_PADX_CTL0(index)); @@ -748,6 +755,8 @@ static void tegra186_utmi_pad_power_down(struct phy *phy) udelay(2);

• clear_bit(index, priv->utmi_pad_enabled);

and here.

Thierry