linux-kernel - Re: [PATCH v4 2/3] arm: shmobile: Add the R9A06G032 SMP enabler driver

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Date:   Wed, 6 Jun 2018 21:46:21 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Michel Pollet <michel.pollet@...renesas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Simon Horman <horms@...ge.net.au>,
        Michel Pollet <buserror+upstream@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Douglas Anderson <dianders@...omium.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Magnus Damm <magnus.damm@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Carlo Caione <carlo@...lessm.com>,
        Andreas Färber <afaerber@...e.de>,
        Frank Rowand <frank.rowand@...y.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/3] arm: shmobile: Add the R9A06G032 SMP enabler driver

Hi Florian,

On Wed, Jun 6, 2018 at 9:37 PM, Florian Fainelli <f.fainelli@...il.com> wrote:
> On 06/06/2018 12:30 PM, Frank Rowand wrote:
>> On 06/05/18 23:36, Michel Pollet wrote:
>>> On 05 June 2018 18:34, Frank wrote:
>>>> On 06/05/18 04:28, Michel Pollet wrote:
>>>>> The Renesas R9A06G032 second CA7 is parked in a ROM pen at boot time,
>>>>> it requires a special enable method to get it started.
>>>>>
>>>>> Signed-off-by: Michel Pollet <michel.pollet@...renesas.com>

>>>>> --- /dev/null
>>>>> +++ b/arch/arm/mach-shmobile/smp-r9a06g032.c

>>>>> +/*
>>>>> + * The second CPU is parked in ROM at boot time. It requires waking
>>>>> +it after
>>>>> + * writing an address into the BOOTADDR register of sysctrl.
>>>>> + *
>>>>> + * So the default value of the "cpu-release-addr" corresponds to
>>>> BOOTADDR...
>>>>> + *
>>>>> + * *However* the BOOTADDR register is not available when the kernel
>>>>> + * starts in NONSEC mode.
>>>>> + *
>>>>> + * So for NONSEC mode, the bootloader re-parks the second CPU into a
>>>>> +pen
>>>>> + * in SRAM, and changes the "cpu-release-addr" of linux's DT to a
>>>>> +SRAM address,
>>>>> + * which is not restricted.
>>>>
>>>> The binding document for cpu-release-addr does not have a definition for 32
>>>> bit arm.  The existing definition is only 64 bit arm.  Please add the definition
>>>> for 32 bit arm to patch 1.
>>>
>>> Hmmm I do find a definition in
>>> Documentation/devicetree/bindings/arm/cpus.txt -- just under where I
>>> added my 'enable-method' -- And it is already used as 32 bits in at least
>>> arch/arm/boot/dts/stih407-family.dtsi.
>>
>> From cpus.txt:
>>
>>         - cpu-release-addr
>>                 Usage: required for systems that have an "enable-method"
>>                        property value of "spin-table".
>>                 Value type: <prop-encoded-array>
>>                 Definition:
>>                         # On ARM v8 64-bit systems must be a two cell
>>                           property identifying a 64-bit zero-initialised
>>                           memory location.
>>
>> The definition specifies a two cell property for 64-bit systems.
>>
>> Please add to the definition that cpu-release-addr is a one cell property
>> for 32-bit systems.
>
> Or maybe phrase it such that the number of cells encoded in
> cpu-release-addr must exactly match the CPU node's #address-cells size?

The CPU node's #address-cells size is unrelated.
You need the #address-cells value from the SoC bus (typically the root
node, not considering heterogeneous systems with multiple CPUs ;-).

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds