On Wed, 12 May 2021, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> The patch below does not apply to the 5.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Hmm, I can see it's commit 8fa5a93a74fa and commit 8b2055c13731 in
queue/5.10 and linux-5.10.y respectively, so I guess it did apply after
all, right? I've sent a version for 5.4-stable and earlier separately.
Maciej
> ------------------ original commit in Linus's tree ------------------
>
> >From 193ced4a79599352d63cb8c9e2f0c6043106eb6a Mon Sep 17 00:00:00 2001
> From: "Maciej W. Rozycki" <macro@xxxxxxxxxxx>
> Date: Wed, 10 Mar 2021 13:03:14 +0100
> Subject: [PATCH] FDDI: defxx: Make MMIO the configuration default except for
> EISA
>
> Recent versions of the PCI Express specification have deprecated support
> for I/O transactions and actually some PCIe host bridges, such as Power
> Systems Host Bridge 4 (PHB4), do not implement them.
>
> The default kernel configuration choice for the defxx driver is the use
> of I/O ports rather than MMIO for PCI and EISA systems. It may have
> made sense as a conservative backwards compatible choice back when MMIO
> operation support was added to the driver as a part of TURBOchannel bus
> support. However nowadays this configuration choice makes the driver
> unusable with systems that do not implement I/O transactions for PCIe.
>
> Make DEFXX_MMIO the configuration default then, except where configured
> for EISA. This exception is because an EISA adapter can have its MMIO
> decoding disabled with ECU (EISA Configuration Utility) and therefore
> not available with the resource allocation infrastructure we implement,
> while port I/O is always readily available as it uses slot-specific
> addressing, directly mapped to the slot an option card has been placed
> in and handled with our EISA bus support core. Conversely a kernel that
> supports modern systems which may not have I/O transactions implemented
> for PCIe will usually not be expected to handle legacy EISA systems.
>
> The change of the default will make it easier for people, including but
> not limited to distribution packagers, to make a working choice for the
> driver.
>
> Update the option description accordingly and while at it replace the
> potentially ambiguous PIO acronym with IOP for "port I/O" vs "I/O ports"
> according to our nomenclature used elsewhere.
>
> Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxx>
> Fixes: e89a2cfb7d7b ("[TC] defxx: TURBOchannel support")
> Cc: stable@xxxxxxxxxxxxxxx # v2.6.21+
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
>
> diff --git a/drivers/net/fddi/Kconfig b/drivers/net/fddi/Kconfig
> index f722079dfb6a..f99c1048c97e 100644
> --- a/drivers/net/fddi/Kconfig
> +++ b/drivers/net/fddi/Kconfig
> @@ -40,17 +40,20 @@ config DEFXX
>
> config DEFXX_MMIO
> bool
> - prompt "Use MMIO instead of PIO" if PCI || EISA
> + prompt "Use MMIO instead of IOP" if PCI || EISA
> depends on DEFXX
> - default n if PCI || EISA
> + default n if EISA
> default y
> help
> This instructs the driver to use EISA or PCI memory-mapped I/O
> - (MMIO) as appropriate instead of programmed I/O ports (PIO).
> + (MMIO) as appropriate instead of programmed I/O ports (IOP).
> Enabling this gives an improvement in processing time in parts
> - of the driver, but it may cause problems with EISA (DEFEA)
> - adapters. TURBOchannel does not have the concept of I/O ports,
> - so MMIO is always used for these (DEFTA) adapters.
> + of the driver, but it requires a memory window to be configured
> + for EISA (DEFEA) adapters that may not always be available.
> + Conversely some PCIe host bridges do not support IOP, so MMIO
> + may be required to access PCI (DEFPA) adapters on downstream PCI
> + buses with some systems. TURBOchannel does not have the concept
> + of I/O ports, so MMIO is always used for these (DEFTA) adapters.
>
> If unsure, say N.
>
>
