linux-kernel - Re: [PATCH v4 0/2] PCI: Fix the issue of failed speed limit lifting

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Message-ID:
 <SEZPR01MB452764342165B17819AAF554A8C22@SEZPR01MB4527.apcprd01.prod.exchangelabs.com>
Date: Wed, 26 Feb 2025 20:20:26 +0800
From: Jiwei Sun <sunjw10@...look.com>
To: Jiwei Sun <sjiwei@....com>, macro@...am.me.uk,
 ilpo.jarvinen@...ux.intel.com, bhelgaas@...gle.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 helgaas@...nel.org, lukas@...ner.de, ahuang12@...ovo.com,
 sunjw10@...ovo.com, jiwei.sun.bj@...com
Subject: Re: [PATCH v4 0/2] PCI: Fix the issue of failed speed limit lifting



On 1/23/25 13:51, Jiwei Sun wrote:
> From: Jiwei Sun <sunjw10@...ovo.com>
> 
> Since commit de9a6c8d5dbf ("PCI/bwctrl: Add pcie_set_target_speed() to set
> PCIe Link Speed"), there are two potential issues in the function
> pcie_failed_link_retrain().
> 
> (1) The macro PCIE_LNKCTL2_TLS2SPEED() and PCIE_LNKCAP_SLS2SPEED() just
> use the link speed field of the registers. However, there are many other
> different function fields in the Link Control 2 Register or the Link
> Capabilities Register. If the register value is directly used by the two
> macros, it may cause getting an error link speed value (PCI_SPEED_UNKNOWN).
> 
> (2) In the pcie_failed_link_retrain(), the local variable lnkctl2 is not
> changed after reading from PCI_EXP_LNKCTL2. It might cause that the
> removing 2.5GT/s downstream link speed restriction codes are not executed.
> 
> In order to avoid the above-mentioned potential issues, only keep link
> speed field of the two registers before using and reread the Link Control 2
> Register before using.
> 
> This series focuses on the first patch of the original series [1]. The
> second one of the original series will submitted via the other single
> patch.
> 
> [1] https://lore.kernel.org/linux-pci/tencent_DD9CBE5B44210B43A04EF8DAF52506A08509@qq.com/
> ---
> v4 changes:
>  - rename the variable name in the macro
> 
> v3 changes:
>  - add fix tag in the commit messages of first patch
>  - add an empty line after the local variable definition in the macro
>  - adjust the position of reading the Link Control 2 register in the code
> 
> v2 changes:
>  - divide the two issues into different patches
>  - get fixed inside the macros
> 
> Jiwei Sun (2):
>   PCI: Fix the wrong reading of register fields
>   PCI: Adjust the position of reading the Link Control 2 register
> 
>  drivers/pci/pci.h    | 32 +++++++++++++++++++-------------
>  drivers/pci/quirks.c |  6 ++++--
>  2 files changed, 23 insertions(+), 15 deletions(-)
> 

Gentle ping.

Thanks,
Regards,
Jiwei