[PATCH v10] usb: dwc3: debugfs: Resume dwc3 before accessing registers

[Udipto Goswami <quic_ugoswami@quicinc.com>]

When the dwc3 device is runtime suspended, various required clocks are in
disabled state 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.

Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
Cc: stable@vger.kernel.org #3.2: 30332eeefec8: debugfs: regset32: Add Runtime PM support
Signed-off-by: Udipto Goswami <quic_ugoswami@quicinc.com>
---
v10: Re-wrote the subject & the commit text along with the dependency.
v9: Fixed function dwc3_rx_fifo_size_show & return values in function
	dwc3_link_state_write along with minor changes for code symmetry.
v8: Replace pm_runtime_get_sync with pm_runtime_resume_and get.
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 | 109 +++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
index e4a2560b9dc0..ebf03468fac4 100644
--- a/drivers/usb/dwc3/debugfs.c
+++ b/drivers/usb/dwc3/debugfs.c
@@ -332,6 +332,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
@@ -350,6 +355,8 @@ static int dwc3_lsp_show(struct seq_file *s, void *unused)
 	}
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
+
 	return 0;
 }
 
@@ -395,6 +402,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_GCTL);
@@ -414,6 +426,8 @@ 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 +477,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
@@ -493,6 +512,8 @@ 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 +530,7 @@ 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 +548,16 @@ static ssize_t dwc3_testmode_write(struct file *file,
 	else
 		testmode = 0;
 
+	ret = pm_runtime_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +576,18 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +600,8 @@ 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 +620,7 @@ 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;
@@ -603,10 +640,15 @@ static ssize_t dwc3_link_state_write(struct file *file,
 	else
 		return -EINVAL;
 
+	ret = pm_runtime_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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);
+		pm_runtime_put_sync(dwc->dev);
 		return -EINVAL;
 	}
 
@@ -616,12 +658,15 @@ 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);
+		pm_runtime_put_sync(dwc->dev);
 		return -EINVAL;
 	}
 
 	dwc3_gadget_set_link_state(dwc, state);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
+	pm_runtime_put_sync(dwc->dev);
+
 	return count;
 }
 
@@ -645,6 +690,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_TXFIFO);
@@ -657,6 +707,8 @@ 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 +719,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	val = dwc3_core_fifo_space(dep, DWC3_RXFIFO);
@@ -679,6 +736,8 @@ 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 +747,19 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +769,19 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +791,19 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +813,19 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +835,19 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		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 +892,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	if (dep->number <= 1) {
@@ -827,6 +926,8 @@ 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 +940,11 @@ 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_resume_and_get(dwc->dev);
+	if (ret < 0)
+		return ret;
 
 	spin_lock_irqsave(&dwc->lock, flags);
 	reg = DWC3_GDBGLSPMUX_EPSELECT(dep->number);
@@ -851,6 +957,8 @@ 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 +1018,7 @@ 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