usb: dwc3: debugfs: Dump internal states

Hi Felipe,

On 11/5/2018 11:35 PM, Felipe Balbi wrote:

Hi,

Thinh Nguyen [off-list ref] writes:

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+static int dwc3_internal_states_show(struct seq_file *s, void *unused)
+{
+	struct dwc3		*dwc = s->private;
+	unsigned int		current_mode;
+	unsigned long		flags;
+	u32			reg;
+
+	spin_lock_irqsave(&dwc->lock, flags);
+	reg = dwc3_readl(dwc->regs, DWC3_GSTS);
+	current_mode = DWC3_GSTS_CURMOD(reg);
+
+	reg = dwc3_readl(dwc->regs, DWC3_GDBGBMU);
+	spin_unlock_irqrestore(&dwc->lock, flags);
+
+	seq_printf(s, "GDBGBMU = 0x%08x\n", reg);

shouldn't the print be done with locks held?

I think the lock for the prints should be held at a higher level.
Otherwise, I don't think it will make a difference using dwc->lock.

what happens if this gets preempted when you release the lock and
a different thread writes to internal_states and reads the result before
$this thread?

I see.

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+static ssize_t dwc3_internal_states_write(struct file *file,
+		const char __user *ubuf, size_t count, loff_t *ppos)

why is this necessary? Seems like it would be nicer to create a
directory structure if the current operating mode is host so that we
don't need to write anything.

Can you clarify more about the directory structure? Actually, I was
wondering what's the best way to do this also. The reason I want to
write to it is because the LSP selection for host is quite large (2^14).

right, turn each of those into a directory of its own. If you don't want
to or can't disclose proper names for those directories, just call them
lsp0, lsp1, lsp2, and so on. Then a read of the file under lsp1
directory would write and read the correct registers.

Everything remains read-only.

This means that there will be 16384 + 256 files create for host. It also
means that we need to kmalloc at least (16384 + 256) * (size of each
selection) so that each file knows what to print. On top of that, when
we change mode of operation (e.g. device->host), then we need to
create/destroy all these files. Is this the way to do it?

Thanks,

Thinh