linux-kernel - Re: [PATCH 4/8] pinctrl: qcom: sdm845: Provide ACPI support

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Date:   Wed, 5 Jun 2019 12:06:14 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     alokc@...eaurora.org, kramasub@...eaurora.org,
        andy.gross@...aro.org, david.brown@...aro.org,
        wsa+renesas@...g-engineering.com, linus.walleij@...aro.org,
        balbi@...nel.org, gregkh@...uxfoundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        jlhugo@...il.com, linux-i2c@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH 4/8] pinctrl: qcom: sdm845: Provide ACPI support

On Wed 05 Jun 00:31 PDT 2019, Lee Jones wrote:

> On Tue, 04 Jun 2019, Bjorn Andersson wrote:
> 
> > On Tue 04 Jun 03:44 PDT 2019, Lee Jones wrote:
> > 
> > > This patch provides basic support for booting with ACPI instead
> > > of the currently supported Device Tree.  When doing so there are a
> > > couple of differences which we need to taken into consideration.
> > > 
> > > Firstly, the SDM850 ACPI tables omit information pertaining to the
> > > 4 reserved GPIOs on the platform.  If Linux attempts to touch/
> > > initialise any of these lines, the firmware will restart the
> > > platform.
> > > 
> > > Secondly, when booting with ACPI, it is expected that the firmware
> > > will set-up things like; Regulators, Clocks, Pin Functions, etc in
> > > their ideal configuration.  Thus, the possible Pin Functions
> > > available to this platform are not advertised when providing the
> > > higher GPIOD/Pinctrl APIs with pin information.
> > > 
> > > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > > ---
> > >  drivers/pinctrl/qcom/Kconfig          |  2 +-
> > >  drivers/pinctrl/qcom/pinctrl-sdm845.c | 35 ++++++++++++++++++++++++++-
> > >  2 files changed, 35 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/pinctrl/qcom/Kconfig b/drivers/pinctrl/qcom/Kconfig
> > > index 2e66ab72c10b..aafbe932424f 100644
> > > --- a/drivers/pinctrl/qcom/Kconfig
> > > +++ b/drivers/pinctrl/qcom/Kconfig
> > > @@ -168,7 +168,7 @@ config PINCTRL_SDM660
> > >  
> > >  config PINCTRL_SDM845
> > >         tristate "Qualcomm Technologies Inc SDM845 pin controller driver"
> > > -       depends on GPIOLIB && OF
> > > +       depends on GPIOLIB && (OF || ACPI)
> > >         select PINCTRL_MSM
> > >         help
> > >           This is the pinctrl, pinmux, pinconf and gpiolib driver for the
> > > diff --git a/drivers/pinctrl/qcom/pinctrl-sdm845.c b/drivers/pinctrl/qcom/pinctrl-sdm845.c
> > > index c97f20fca5fd..7188bee3cf3e 100644
> > > --- a/drivers/pinctrl/qcom/pinctrl-sdm845.c
> > > +++ b/drivers/pinctrl/qcom/pinctrl-sdm845.c
> > > @@ -3,6 +3,7 @@
> > >   * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
> > >   */
> > >  
> > > +#include <linux/acpi.h>
> > >  #include <linux/module.h>
> > >  #include <linux/of.h>
> > >  #include <linux/platform_device.h>
> > > @@ -1277,6 +1278,10 @@ static const struct msm_pingroup sdm845_groups[] = {
> > >  	UFS_RESET(ufs_reset, 0x99f000),
> > >  };
> > >  
> > > +static const int sdm845_acpi_reserved_gpios[] = {
> > > +	0, 1, 2, 3, 81, 82, 83, 84, -1
> > > +};
> > > +
> > >  static const struct msm_pinctrl_soc_data sdm845_pinctrl = {
> > >  	.pins = sdm845_pins,
> > >  	.npins = ARRAY_SIZE(sdm845_pins),
> > > @@ -1284,14 +1289,41 @@ static const struct msm_pinctrl_soc_data sdm845_pinctrl = {
> > >  	.nfunctions = ARRAY_SIZE(sdm845_functions),
> > >  	.groups = sdm845_groups,
> > >  	.ngroups = ARRAY_SIZE(sdm845_groups),
> > > +	.reserved_gpios = sdm845_acpi_reserved_gpios,
> > 
> > The reason why put these in DT is because the list is board/firmware
> > dependent. E.g. the firmware on db845c does not support the peripherals
> > that sits on these 8 pins and as such these are not reserved.
> 
> If we need to be more particular about which platform(s) this affects,
> we could add matching based on their differences (some ACPI HID or F/W
> version/descriptor, etc) as and when we enable them for booting with
> ACPI.
> 

You're making an assumption that all SDM845 (the platform) devices using
ACPI will have this list of GPIOs reserved for secure firmware to use,
this is questionable but I don't have any better suggestion.

But you do this by adding a new struct msm_pinctrl_soc_data
sdm845_acpi_pinctrl, specifically for the ACPI case. And then, on the
line I object to here, you add this list as the list of reserved GPIOs
for the DT case as well.

> > But given that the two structs looks identical now, did you perhaps not
> > intend to add.reserved_gpios for the non-ACPI case?
> 
> Given your example above, I think it's best that we let the
> configuration tables advertise these in the first instance.  I only
> add them here because it is not possible to obtain them from
> elsewhere.
> 

Then add it for ACPI only - which I still presume you intended to do by
adding sdm845_acpi_pinctrl (which is now identical to sdm845_pinctrl).

Regards,
Bjorn