[PATCH v7] usb: dwc3: debugfs: Prevent any register access when devices is runtime suspended

[Udipto Goswami <quic_ugoswami@quicinc.com>]

When the dwc3 device is runtime suspended, various required clocks would
get disabled and it is not guaranteed that access to any registers would
work. Depending on the SoC glue, a register read could be as benign as
returning 0 or be fatal enough to hang the system.

In order to prevent such scenarios of fatal errors, make sure to resume
dwc3 then allow the function to proceed.

Signed-off-by: Udipto Goswami <quic_ugoswami@quicinc.com>
---
v7: Replaced pm_runtime_put with pm_runtime_put_sync & returned proper values.
v6: Added changes to handle get_dync failure appropriately.
v5: Reworked the patch to resume dwc3 while accessing the registers.
v4: Introduced pm_runtime_get_if_in_use in order to make sure dwc3 isn't
	suspended while accessing the registers.
v3: Replace pr_err to dev_err. 
v2: Replaced return 0 with -EINVAL & seq_puts with pr_err.

 drivers/usb/dwc3/debugfs.c | 128 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 126 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
index e4a2560b9dc0..859184de37b6 100644
--- a/drivers/usb/dwc3/debugfs.c
+++ b/drivers/usb/dwc3/debugfs.c
@@ -332,6 +332,13 @@ static int dwc3_lsp_show(struct seq_file *s, void *unused)
 	unsigned int		current_mode;
 	unsigned long		flags;
 	u32			reg;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
@@ -349,6 +356,7 @@ static int dwc3_lsp_show(struct seq_file *s, void *unused)
 		break;
 	}
 	spin_unlock_irqrestore(&dwc->lock, flags);
+	pm_runtime_put_sync(dwc->dev);
 
 	return 0;
 }
@@ -395,6 +403,13 @@ static int dwc3_mode_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = s->private;
 	unsigned long		flags;
 	u32			reg;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
@@ -414,6 +429,7 @@ static int dwc3_mode_show(struct seq_file *s, void *unused)
 		seq_printf(s, "UNKNOWN %08x\n", DWC3_GCTL_PRTCAP(reg));
 	}
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -463,6 +479,13 @@ static int dwc3_testmode_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = s->private;
 	unsigned long		flags;
 	u32			reg;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
@@ -493,6 +516,7 @@ static int dwc3_testmode_show(struct seq_file *s, void *unused)
 		seq_printf(s, "UNKNOWN %d\n", reg);
 	}
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -509,6 +533,7 @@ static ssize_t dwc3_testmode_write(struct file *file,
 	unsigned long		flags;
 	u32			testmode = 0;
 	char			buf[32];
+	int			ret;
 
 	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
 		return -EFAULT;
@@ -526,10 +551,17 @@ static ssize_t dwc3_testmode_write(struct file *file,
 	else
 		testmode = 0;
 
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	dwc3_gadget_set_test_mode(dwc, testmode);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return count;
 }
 
@@ -548,12 +580,20 @@ static int dwc3_link_state_show(struct seq_file *s, void *unused)
 	enum dwc3_link_state	state;
 	u32			reg;
 	u8			speed;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
 	if (DWC3_GSTS_CURMOD(reg) != DWC3_GSTS_CURMOD_DEVICE) {
 		seq_puts(s, "Not available\n");
 		spin_unlock_irqrestore(&dwc->lock, flags);
+		pm_runtime_put_sync(dwc->dev);
 		return 0;
 	}
 
@@ -566,6 +606,7 @@ static int dwc3_link_state_show(struct seq_file *s, void *unused)
 		   dwc3_gadget_hs_link_string(state));
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -584,6 +625,7 @@ static ssize_t dwc3_link_state_write(struct file *file,
 	char			buf[32];
 	u32			reg;
 	u8			speed;
+	int			ret;
 
 	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
 		return -EFAULT;
@@ -603,11 +645,18 @@ static ssize_t dwc3_link_state_write(struct file *file,
 	else
 		return -EINVAL;
 
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
 	if (DWC3_GSTS_CURMOD(reg) != DWC3_GSTS_CURMOD_DEVICE) {
 		spin_unlock_irqrestore(&dwc->lock, flags);
-		return -EINVAL;
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
 	}
 
 	reg = dwc3_readl(dwc->regs, DWC3_DSTS);
@@ -616,12 +665,14 @@ static ssize_t dwc3_link_state_write(struct file *file,
 	if (speed < DWC3_DSTS_SUPERSPEED &&
 	    state != DWC3_LINK_STATE_RECOV) {
 		spin_unlock_irqrestore(&dwc->lock, flags);
-		return -EINVAL;
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
 	}
 
 	dwc3_gadget_set_link_state(dwc, state);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return count;
 }
 
@@ -645,6 +696,13 @@ static int dwc3_tx_fifo_size_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			mdwidth;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_TXFIFO);
@@ -657,6 +715,7 @@ static int dwc3_tx_fifo_size_show(struct seq_file *s, void *unused)
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -667,6 +726,13 @@ static int dwc3_rx_fifo_size_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			mdwidth;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXFIFO);
@@ -679,6 +745,7 @@ static int dwc3_rx_fifo_size_show(struct seq_file *s, void *unused)
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -688,12 +755,20 @@ static int dwc3_tx_request_queue_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = dep->dwc;
 	unsigned long		flags;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_TXREQQ);
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -703,12 +778,20 @@ static int dwc3_rx_request_queue_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = dep->dwc;
 	unsigned long		flags;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXREQQ);
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -718,12 +801,20 @@ static int dwc3_rx_info_queue_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = dep->dwc;
 	unsigned long		flags;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXINFOQ);
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -733,12 +824,20 @@ static int dwc3_descriptor_fetch_queue_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = dep->dwc;
 	unsigned long		flags;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_DESCFETCHQ);
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -748,12 +847,20 @@ static int dwc3_event_queue_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = dep->dwc;
 	unsigned long		flags;
 	u32			val;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_EVENTQ);
 	seq_printf(s, "%u\n", val);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -798,6 +905,13 @@ static int dwc3_trb_ring_show(struct seq_file *s, void *unused)
 	struct dwc3		*dwc = dep->dwc;
 	unsigned long		flags;
 	int			i;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	if (dep->number <= 1) {
@@ -827,6 +941,7 @@ static int dwc3_trb_ring_show(struct seq_file *s, void *unused)
 out:
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -839,6 +954,13 @@ static int dwc3_ep_info_register_show(struct seq_file *s, void *unused)
 	u32			lower_32_bits;
 	u32			upper_32_bits;
 	u32			reg;
+	int			ret;
+
+	ret = pm_runtime_get_sync(dwc->dev);
+	if (ret < 0) {
+		pm_runtime_put_sync(dwc->dev);
+		return ret;
+	}
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = DWC3_GDBGLSPMUX_EPSELECT(dep->number);
@@ -851,6 +973,7 @@ static int dwc3_ep_info_register_show(struct seq_file *s, void *unused)
 	seq_printf(s, "0x%016llx\n", ep_info);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
 	return 0;
 }
 
@@ -910,6 +1033,7 @@ void dwc3_debugfs_init(struct dwc3 *dwc)
 	dwc->regset->regs = dwc3_regs;
 	dwc->regset->nregs = ARRAY_SIZE(dwc3_regs);
 	dwc->regset->base = dwc->regs - DWC3_GLOBALS_REGS_START;
+	dwc->regset->dev = dwc->dev;
 
 	root = debugfs_create_dir(dev_name(dwc->dev), usb_debug_root);
 	dwc->debug_root = root;
-- 
2.17.1