From: Lee Jones <lee.jones@linaro.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: alokc@codeaurora.org, Andy Gross <andy.gross@linaro.org>,
David Brown <david.brown@linaro.org>,
wsa+renesas@sang-engineering.com,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Linus Walleij <linus.walleij@linaro.org>,
balbi@kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jeffrey Hugo <jlhugo@gmail.com>,
linux-i2c <linux-i2c@vger.kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
linux-usb <linux-usb@vger.kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 4/8] pinctrl: qcom: sdm845: Provide ACPI support
Date: Mon, 10 Jun 2019 10:22:45 +0100 [thread overview]
Message-ID: <20190610092245.GN4797@dell> (raw)
In-Reply-To: <CAKv+Gu8rhxciy1cOG3B3pda9+p4R_COGrrqa7S_Rj9y2HeBxYw@mail.gmail.com>
On Mon, 10 Jun 2019, Ard Biesheuvel wrote:
> On Mon, 10 Jun 2019 at 10:55, Lee Jones <lee.jones@linaro.org> wrote:
> >
> > On Mon, 10 Jun 2019, Ard Biesheuvel wrote:
> >
> > > On Mon, 10 Jun 2019 at 10:42, Lee Jones <lee.jones@linaro.org> 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@linaro.org>
> > >
> > > For the ACPI probing boilerplate:
> > > Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > >
> > > *However*, I really don't like hardcoding reserved GPIOs like this.
> > > What guarantee do we have that each and every ACPI system
> > > incorporating the QCOM0217 device has the exact same list of reserved
> > > GPIOs?
> >
> > This is SDM845 specific, so the chances are reduced.
>
> You don't know that.
All the evidence I have to hand tells me that this is the case. Even
on very closely related variants Qualcomm uses different H/W blocks
for GPIO.
> > However, if another SDM845 variant does crop up, also lacking the
> > "gpios" property, we will have to find another differentiating factor
> > between them and conduct some matching. What else can you do with
> > platforms supporting non-complete/non-forthcoming ACPI tables?
> >
>
> Either we don't touch any pins at all if they are not referenced
> explicitly anywhere
I guess this would require an API change, which is out of scope of
this patch-set. Happy to change this implementation later if the
subsystem allows for it though.
> or we parse the PEP tables, which seem to cover
> some of this information (if Bjorn's analysis is correct)
Maybe someone can conduct some further work on this when we start to
enable or write a driver for the PEP (Windows-compatible System Power
Management Controller). The tables for the PEP look pretty complex,
so this task would be extremely difficult if not impossible without
Qualcomm's help. I wouldn't even know how to extrapolate this
information from the tables.
> (if Bjorn's analysis is correct)
Bjorn is about to provide his Reviewed-by for this implementation.
--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2019-06-10 9:22 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 8:42 [PATCH v3 1/8] i2c: i2c-qcom-geni: Provide support for ACPI Lee Jones
2019-06-10 8:42 ` [PATCH v3 2/8] i2c: i2c-qcom-geni: Signify successful driver probe Lee Jones
2019-06-11 19:40 ` Bjorn Andersson
2019-06-10 8:42 ` [PATCH v3 3/8] pinctrl: msm: Add ability for drivers to supply a reserved GPIO list Lee Jones
2019-06-12 7:25 ` Linus Walleij
2019-06-10 8:42 ` [PATCH v3 4/8] pinctrl: qcom: sdm845: Provide ACPI support Lee Jones
2019-06-10 8:46 ` Ard Biesheuvel
2019-06-10 8:55 ` Lee Jones
2019-06-10 9:03 ` Ard Biesheuvel
2019-06-10 9:22 ` Lee Jones [this message]
2019-06-10 10:20 ` Ard Biesheuvel
2019-06-11 18:39 ` Bjorn Andersson
2019-06-12 7:18 ` Linus Walleij
2019-06-11 18:40 ` Bjorn Andersson
2019-06-10 8:42 ` [PATCH v3 5/8] soc: qcom: geni: Add support for ACPI Lee Jones
2019-06-10 8:47 ` Ard Biesheuvel
2019-06-10 8:42 ` [PATCH v3 6/8] usb: dwc3: qcom: Add support for booting with ACPI Lee Jones
2019-06-10 8:42 ` [PATCH v3 7/8] usb: dwc3: qcom: Start USB in 'host mode' on the SDM845 Lee Jones
2019-06-11 22:33 ` Bjorn Andersson
2019-06-12 5:57 ` Lee Jones
2019-06-10 8:42 ` [PATCH v3 8/8] usb: dwc3: qcom: Improve error handling Lee Jones
2019-06-10 8:44 ` [PATCH v3 1/8] i2c: i2c-qcom-geni: Provide support for ACPI Ard Biesheuvel
2019-06-12 10:34 ` Wolfram Sang
2019-06-12 10:40 ` Lee Jones
2019-06-12 10:44 ` Wolfram Sang
2019-06-13 8:52 ` Lee Jones
2019-06-13 8:52 ` Lee Jones
2019-06-13 9:19 ` Wolfram Sang
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