PciLib/PciExpressLib: 64-bit r/w functions

PciLib/PciExpressLib: 64-bit r/w functions

[Marvin H?user]

Dear developers,

While browsing the KabylakeSiPkg code, I noticed that 64-bit registers are read directly via MmioRead64() as there is no PciRead64() function.
Is there a specific reason there are no PciRead64() and PciExpressRead64() functions or were they simply not needed previously?

Thanks and regards,
Marvin.

Re: PciLib/PciExpressLib: 64-bit r/w functions

[Laszlo Ersek]

On 08/05/17 23:38, Marvin H?user wrote:
> Dear developers,
> 
> While browsing the KabylakeSiPkg code, I noticed that 64-bit registers are read directly via MmioRead64() as there is no PciRead64() function.
> Is there a specific reason there are no PciRead64() and PciExpressRead64() functions or were they simply not needed previously?

Validity of 64-bit accesses to PCI config space is platform dependent
[*] and I guess the PciLib designers didn't want to deviate from the
common interface pattern that PciReadXX() always succeeds (as long as
the input parameter is valid), regardless of XX.

[*] The UEFI spec repeats the following paragraph in several places:

    The I/O operations are carried out exactly as requested. The caller
    is responsible satisfying any alignment and I/O width restrictions
    that the PCI controller on a platform might require. For example on
    some platforms, width requests of EfiPciIoWidthUint64 do not work.

Thanks
Laszlo

Re: PciLib/PciExpressLib: 64-bit r/w functions

[Marvin Häuser]

Thank you for your reply!

Sorry, I was only thinking of MMIO access when I wrote the mail, should have limited it to PciExpressLib.
I did not hear of any platform supporting MMIO but not 64-bit register r/w, will research that.

Regards,
Marvin.

> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Sunday, August 6, 2017 1:35 PM
> To: Marvin Häuser <Marvin.Haeuser@outlook.com>
> Cc: edk2-devel@lists.01.org
> Subject: Re: [edk2] PciLib/PciExpressLib: 64-bit r/w functions
> 
> On 08/05/17 23:38, Marvin H?user wrote:
> > Dear developers,
> >
> > While browsing the KabylakeSiPkg code, I noticed that 64-bit registers are
> read directly via MmioRead64() as there is no PciRead64() function.
> > Is there a specific reason there are no PciRead64() and PciExpressRead64()
> functions or were they simply not needed previously?
> 
> Validity of 64-bit accesses to PCI config space is platform dependent [*] and I
> guess the PciLib designers didn't want to deviate from the common interface
> pattern that PciReadXX() always succeeds (as long as the input parameter is
> valid), regardless of XX.
> 
> [*] The UEFI spec repeats the following paragraph in several places:
> 
>     The I/O operations are carried out exactly as requested. The caller
>     is responsible satisfying any alignment and I/O width restrictions
>     that the PCI controller on a platform might require. For example on
>     some platforms, width requests of EfiPciIoWidthUint64 do not work.
> 
> Thanks
> Laszlo