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

[Udipto Goswami <quic_ugoswami@xxxxxxxxxxx>]

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, bail out of debugfs
function is dwc3 is suspended.

Signed-off-by: Udipto Goswami <quic_ugoswami@xxxxxxxxxxx>
---
 drivers/usb/dwc3/debugfs.c | 50 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
index 850df0e6bcab..f921d4911ffc 100644
--- a/drivers/usb/dwc3/debugfs.c
+++ b/drivers/usb/dwc3/debugfs.c
@@ -544,6 +544,11 @@ static int dwc3_link_state_show(struct seq_file *s, void *unused)
 	u32			reg;
 	u8			speed;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
 	if (DWC3_GSTS_CURMOD(reg) != DWC3_GSTS_CURMOD_DEVICE) {
@@ -580,6 +585,11 @@ static ssize_t dwc3_link_state_write(struct file *file,
 	u32			reg;
 	u8			speed;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
 		return -EFAULT;
 
@@ -641,6 +651,11 @@ static int dwc3_tx_fifo_size_show(struct seq_file *s, void *unused)
 	u32			mdwidth;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_TXFIFO);
 
@@ -663,6 +678,11 @@ static int dwc3_rx_fifo_size_show(struct seq_file *s, void *unused)
 	u32			mdwidth;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXFIFO);
 
@@ -684,6 +704,11 @@ static int dwc3_tx_request_queue_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_TXREQQ);
 	seq_printf(s, "%u\n", val);
@@ -699,6 +724,11 @@ static int dwc3_rx_request_queue_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXREQQ);
 	seq_printf(s, "%u\n", val);
@@ -714,6 +744,11 @@ static int dwc3_rx_info_queue_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXINFOQ);
 	seq_printf(s, "%u\n", val);
@@ -729,6 +764,11 @@ static int dwc3_descriptor_fetch_queue_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_DESCFETCHQ);
 	seq_printf(s, "%u\n", val);
@@ -744,6 +784,11 @@ static int dwc3_event_queue_show(struct seq_file *s, void *unused)
 	unsigned long		flags;
 	u32			val;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_EVENTQ);
 	seq_printf(s, "%u\n", val);
@@ -835,6 +880,11 @@ static int dwc3_ep_info_register_show(struct seq_file *s, void *unused)
 	u32			upper_32_bits;
 	u32			reg;
 
+	if (pm_runtime_suspended(dwc->dev)) {
+		seq_puts(s, "Invalid operation, DWC3 suspended!");
+		return 0;
+	}
+
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = DWC3_GDBGLSPMUX_EPSELECT(dep->number);
 	dwc3_writel(dwc->regs, DWC3_GDBGLSPMUX, reg);
-- 
2.17.1