linux-kernel - Re: [PATCH v2 1/2] PCI: Fix the wrong reading of register fields

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Message-ID: <8441fdc4-de28-a3ba-27d6-8a5351d4ea19@linux.intel.com>
Date: Thu, 16 Jan 2025 15:52:26 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Jiwei Sun <sjiwei@....com>
cc: macro@...am.me.uk, bhelgaas@...gle.com, linux-pci@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>, helgaas@...nel.org, 
    Lukas Wunner <lukas@...ner.de>, ahuang12@...ovo.com, sunjw10@...ovo.com, 
    jiwei.sun.bj@...com, sunjw10@...look.com
Subject: Re: [PATCH v2 1/2] PCI: Fix the wrong reading of register fields

On Wed, 15 Jan 2025, Jiwei Sun wrote:

> From: Jiwei Sun <sunjw10@...ovo.com>
> 
> The macro PCIE_LNKCTL2_TLS2SPEED() and PCIE_LNKCAP_SLS2SPEED() just uses
> 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).
> 
> In order to avoid the above-mentioned potential issue, only keep link
> speed field of the two registers before using.
>
> Suggested-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Signed-off-by: Jiwei Sun <sunjw10@...ovo.com>

Missing Fixes tag.

> ---
>  drivers/pci/pci.h | 30 +++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 2e40fc63ba31..b7e5af859517 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -337,12 +337,13 @@ void pci_bus_put(struct pci_bus *bus);
>  
>  #define PCIE_LNKCAP_SLS2SPEED(lnkcap)					\
>  ({									\
> -	((lnkcap) == PCI_EXP_LNKCAP_SLS_64_0GB ? PCIE_SPEED_64_0GT :	\
> -	 (lnkcap) == PCI_EXP_LNKCAP_SLS_32_0GB ? PCIE_SPEED_32_0GT :	\
> -	 (lnkcap) == PCI_EXP_LNKCAP_SLS_16_0GB ? PCIE_SPEED_16_0GT :	\
> -	 (lnkcap) == PCI_EXP_LNKCAP_SLS_8_0GB ? PCIE_SPEED_8_0GT :	\
> -	 (lnkcap) == PCI_EXP_LNKCAP_SLS_5_0GB ? PCIE_SPEED_5_0GT :	\
> -	 (lnkcap) == PCI_EXP_LNKCAP_SLS_2_5GB ? PCIE_SPEED_2_5GT :	\
> +	u32 __lnkcap = (lnkcap) & PCI_EXP_LNKCAP_SLS;		\
> +	(__lnkcap == PCI_EXP_LNKCAP_SLS_64_0GB ? PCIE_SPEED_64_0GT :	\

It would be nice to have an empty line here and below as is in "normal 
functions" (obviously the \ continuation at the end of the line is 
required).

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

This is quite important fix IMO.

> +	 __lnkcap == PCI_EXP_LNKCAP_SLS_32_0GB ? PCIE_SPEED_32_0GT :	\
> +	 __lnkcap == PCI_EXP_LNKCAP_SLS_16_0GB ? PCIE_SPEED_16_0GT :	\
> +	 __lnkcap == PCI_EXP_LNKCAP_SLS_8_0GB ? PCIE_SPEED_8_0GT :	\
> +	 __lnkcap == PCI_EXP_LNKCAP_SLS_5_0GB ? PCIE_SPEED_5_0GT :	\
> +	 __lnkcap == PCI_EXP_LNKCAP_SLS_2_5GB ? PCIE_SPEED_2_5GT :	\
>  	 PCI_SPEED_UNKNOWN);						\
>  })
>  
> @@ -357,13 +358,16 @@ void pci_bus_put(struct pci_bus *bus);
>  	 PCI_SPEED_UNKNOWN)
>  
>  #define PCIE_LNKCTL2_TLS2SPEED(lnkctl2) \
> -	((lnkctl2) == PCI_EXP_LNKCTL2_TLS_64_0GT ? PCIE_SPEED_64_0GT : \
> -	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_32_0GT ? PCIE_SPEED_32_0GT : \
> -	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_16_0GT ? PCIE_SPEED_16_0GT : \
> -	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_8_0GT ? PCIE_SPEED_8_0GT : \
> -	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_5_0GT ? PCIE_SPEED_5_0GT : \
> -	 (lnkctl2) == PCI_EXP_LNKCTL2_TLS_2_5GT ? PCIE_SPEED_2_5GT : \
> -	 PCI_SPEED_UNKNOWN)
> +({									\
> +	u16 __lnkctl2 = (lnkctl2) & PCI_EXP_LNKCTL2_TLS;	\
> +	(__lnkctl2 == PCI_EXP_LNKCTL2_TLS_64_0GT ? PCIE_SPEED_64_0GT : \
> +	 __lnkctl2 == PCI_EXP_LNKCTL2_TLS_32_0GT ? PCIE_SPEED_32_0GT : \
> +	 __lnkctl2 == PCI_EXP_LNKCTL2_TLS_16_0GT ? PCIE_SPEED_16_0GT : \
> +	 __lnkctl2 == PCI_EXP_LNKCTL2_TLS_8_0GT ? PCIE_SPEED_8_0GT : \
> +	 __lnkctl2 == PCI_EXP_LNKCTL2_TLS_5_0GT ? PCIE_SPEED_5_0GT : \
> +	 __lnkctl2 == PCI_EXP_LNKCTL2_TLS_2_5GT ? PCIE_SPEED_2_5GT : \
> +	 PCI_SPEED_UNKNOWN);						\
> +})
>  
>  /* PCIe speed to Mb/s reduced by encoding overhead */
>  #define PCIE_SPEED2MBS_ENC(speed) \
> 


-- 
 i.