linux-kernel - Re: [PATCH v6 6/8] PCI: Add TLP Prefix reading into pcie_read_tlp

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Message-ID: <20241211164904.00007a02@huawei.com>
Date: Wed, 11 Dec 2024 16:49:04 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC: <linux-pci@...r.kernel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, "Mahesh
 J Salgaonkar" <mahesh@...ux.ibm.com>, Oliver O'Halloran <oohall@...il.com>,
	Lukas Wunner <lukas@...ner.de>, Krzysztof Wilczyński
	<kw@...ux.com>, <linux-kernel@...r.kernel.org>,
	<linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v6 6/8] PCI: Add TLP Prefix reading into
 pcie_read_tlp_log()

On Fri, 13 Sep 2024 17:36:30 +0300
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> wrote:

> pcie_read_tlp_log() handles only 4 Header Log DWORDs but TLP Prefix Log
> (PCIe r6.1 secs 7.8.4.12 & 7.9.14.13) may also be present.
> 
> Generalize pcie_read_tlp_log() and struct pcie_tlp_log to handle also
> TLP Prefix Log. The relevant registers are formatted identically in AER
> and DPC Capability, but has these variations:
> 
> a) The offsets of TLP Prefix Log registers vary.
> b) DPC RP PIO TLP Prefix Log register can be < 4 DWORDs.
> 
> Therefore callers must pass the offset of the TLP Prefix Log register
> and the entire length to pcie_read_tlp_log() to be able to read the
> correct number of TLP Prefix DWORDs from the correct offset.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

Trivial comments below
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Would have been nice if they'd just made the formats have the
same sized holes etc!

> diff --git a/drivers/pci/pcie/tlp.c b/drivers/pci/pcie/tlp.c
> index 65ac7b5d8a87..def9dd7b73e8 100644
> --- a/drivers/pci/pcie/tlp.c
> +++ b/drivers/pci/pcie/tlp.c
> @@ -11,26 +11,65 @@

>  /**
>   * pcie_read_tlp_log - read TLP Header Log
Maybe update this to read TLP Header and Prefix Logs
>   * @dev: PCIe device
>   * @where: PCI Config offset of TLP Header Log
> + * @where2: PCI Config offset of TLP Prefix Log

Is it worth giving it a more specific name than where2?
Possibly renaming where as well!

> + * @tlp_len: TLP Log length (Header Log + TLP Prefix Log in DWORDs)
>   * @log: TLP Log structure to fill
>   *
>   * Fill @log from TLP Header Log registers, e.g., AER or DPC.
>   *
>   * Return: 0 on success and filled TLP Log structure, <0 on error.
>   */
> -int pcie_read_tlp_log(struct pci_dev *dev, int where,
> -		      struct pcie_tlp_log *log)
> +int pcie_read_tlp_log(struct pci_dev *dev, int where, int where2,
> +		      unsigned int tlp_len, struct pcie_tlp_log *log)
>  {