linux-kernel - Re: [rfc, PATCH v1 0/7] PCI: introduce p2sb helper

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Date:   Thu, 10 Jun 2021 11:02:11 +0200
From:   Henning Schild <henning.schild@...mens.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Jean Delvare <jdelvare@...e.de>,
        Lee Jones <lee.jones@...aro.org>,
        Tan Jui Nee <jui.nee.tan@...el.com>,
        "Jim Quinlan" <james.quinlan@...adcom.com>,
        Jonathan Yong <jonathan.yong@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        <linux-kernel@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, Jean Delvare <jdelvare@...e.com>,
        Peter Tyser <ptyser@...-inc.com>, <hdegoede@...hat.com>
Subject: Re: [rfc, PATCH v1 0/7] PCI: introduce p2sb helper

Am Mon, 8 Mar 2021 14:20:13 +0200
schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:

> There are a few users and even at least one more is coming
> that would like to utilize p2sb mechanisms like hide/unhide
> a device from PCI configuration space.
> 
> Here is the series to deduplicate existing users and provide
> a generic way for new comers.
> 
> It also includes a patch to enable GPIO controllers on Apollo Lake
> when it's used with ABL bootloader w/o ACPI support.

That bit is especially interesting. Making pinctl*lake initialize when
ACPI IDs are missing and p2sb is hidden.

However i have seen pinctl-broxton get confused because it was trying
to come up twice on a system that has the ACPI entries. Once as
"INT3452" and second as "apollolake-pinctrl". They should probably
mutually exclude each other. And the two different names for "the
same"? thing make it impossible to write a driver using those GPIOs.
Unless it would try and look up both variants or not looking up with
gpiochip.label.

I would also need that "enable GPIO w/o ACPI" for skylake. I think it
would be generally useful if the GPIO controllers would be enabled not
depending on ACPI, and coming up with only one "label" to build on top.

regards,
Henning

> Please, comment on the approach and individual patches.
> 
> (Since it's cross subsystem, the PCI seems like a main one and
>  I think it makes sense to route it thru it with immutable tag
>  or branch provided for the others).
> 
> Andy Shevchenko (5):
>   PCI: Introduce pci_bus_*() printing macros when device is not
>     available
>   PCI: Convert __pci_read_base() to __pci_bus_read_base()
>   mfd: lpc_ich: Factor out lpc_ich_enable_spi_write()
>   mfd: lpc_ich: Switch to generic pci_p2sb_bar()
>   i2c: i801: convert to use common P2SB accessor
> 
> Jonathan Yong (1):
>   PCI: New Primary to Sideband (P2SB) bridge support library
> 
> Tan Jui Nee (1):
>   mfd: lpc_ich: Add support for pinctrl in non-ACPI system
> 
>  drivers/i2c/busses/Kconfig    |   1 +
>  drivers/i2c/busses/i2c-i801.c |  40 +++-------
>  drivers/mfd/Kconfig           |   1 +
>  drivers/mfd/lpc_ich.c         | 135
> +++++++++++++++++++++++++++++----- drivers/pci/Kconfig           |
> 8 ++ drivers/pci/Makefile          |   1 +
>  drivers/pci/pci-p2sb.c        |  89 ++++++++++++++++++++++
>  drivers/pci/pci.h             |  13 +++-
>  drivers/pci/probe.c           |  81 ++++++++++----------
>  include/linux/pci-p2sb.h      |  28 +++++++
>  include/linux/pci.h           |   9 +++
>  11 files changed, 313 insertions(+), 93 deletions(-)
>  create mode 100644 drivers/pci/pci-p2sb.c
>  create mode 100644 include/linux/pci-p2sb.h
>