linux-kernel - Re: [PATCH 2/3] PCI: debugfs: Add support for RASDES framework in DWC

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Message-ID: <20240726174123.GA907125@bhelgaas>
Date: Fri, 26 Jul 2024 12:41:23 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Shradha Todi <shradha.t@...sung.com>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	manivannan.sadhasivam@...aro.org, lpieralisi@...nel.org,
	kw@...ux.com, robh@...nel.org, bhelgaas@...gle.com,
	jingoohan1@...il.com, fancer.lancer@...il.com,
	yoshihiro.shimoda.uh@...esas.com, conor.dooley@...rochip.com,
	pankaj.dubey@...sung.com, gost.dev@...sung.com
Subject: Re: [PATCH 2/3] PCI: debugfs: Add support for RASDES framework in DWC

Based on the files touched, this looks DWC-specific, so the subject
prefix should be "PCI: dwc: ", not the very generic "debugfs".
The "debugfs" part could go later, e.g.,

  PCI: dwc: Add RASDES debugfs support

On Tue, Jun 25, 2024 at 03:08:12PM +0530, Shradha Todi wrote:
> Add support to use the RASDES feature of DesignWare PCIe controller
> using debugfs entries.
> 
> RASDES is a vendor specific extended PCIe capability which reads the
> current hardware internal state of PCIe device. Following primary
> features are provided to userspace via debugfs:
> - Debug registers
> - Error injection
> - Statistical counters

This looks like great stuff, thanks a lot for implementing this!

I think this debugfs structure and functionality should be documented
somewhere like Documentation/ABI/testing/.  This functionality is
likely to be used by userspace tools like perf that will depend on
this ABI.  (Oh, sorry, I just saw Jonathan's similar comment, didn't
mean to duplicate it.)

I don't expect other vendors to implement exactly the same
functionality, but we can at least try to use similar structure if
they do.

> +config PCIE_DW_DEBUGFS
> +	bool "DWC PCIe debugfs entries"
> +	help
> +	  Enables debugfs entries for the DWC PCIe Controller.
> +	  These entries make use of the RAS features in the DW
> +	  controller to help in debug, error injection and statistical
> +	  counters

> +int dwc_pcie_rasdes_debugfs_init(struct dw_pcie *pci)
> +{
> +	struct device *dev = pci->dev;
> +	int ras_cap;
> +	struct rasdes_info *dump_info;
> +	char dirname[DWC_DEBUGFS_MAX];
> +	struct dentry *dir, *rasdes_debug, *rasdes_err_inj;
> +	struct dentry *rasdes_event_counter, *rasdes_events;
> +	int i;
> +	struct rasdes_priv *priv_tmp;
> +
> +	ras_cap = dw_pcie_find_vsec_capability(pci, DW_PCIE_RAS_DES_CAP);

Does this look at config space of a DWC Root Port, or is this in a
RCRB or similar?

Bjorn