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

[Rob Herring <robh+dt@kernel.org>]

On Wed, Jun 6, 2018 at 2:30 PM, Frank Rowand <frowand.list@gmail.com> wrote:
> Hi Michel,
>
> On 06/05/18 23:36, Michel Pollet wrote:
>> Hi Frank,
>>
>> 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@bp.renesas.com>
>>>> ---
>>>>  arch/arm/mach-shmobile/Makefile        |  1 +
>>>>  arch/arm/mach-shmobile/smp-r9a06g032.c | 79
>>>> ++++++++++++++++++++++++++++++++++
>>>>  2 files changed, 80 insertions(+)
>>>>  create mode 100644 arch/arm/mach-shmobile/smp-r9a06g032.c
>>>>
>>>> diff --git a/arch/arm/mach-shmobile/Makefile
>>>> b/arch/arm/mach-shmobile/Makefile index 1939f52..d7fc98f 100644
>>>> --- a/arch/arm/mach-shmobile/Makefile
>>>> +++ b/arch/arm/mach-shmobile/Makefile
>>>> @@ -34,6 +34,7 @@ smp-$(CONFIG_ARCH_SH73A0)+= smp-sh73a0.o
>>> headsmp-scu.o platsmp-scu.o
>>>>  smp-$(CONFIG_ARCH_R8A7779)+= smp-r8a7779.o headsmp-scu.o
>>> platsmp-scu.o
>>>>  smp-$(CONFIG_ARCH_R8A7790)+= smp-r8a7790.o
>>>>  smp-$(CONFIG_ARCH_R8A7791)+= smp-r8a7791.o
>>>> +smp-$(CONFIG_ARCH_R9A06G032)+= smp-r9a06g032.o
>>>>  smp-$(CONFIG_ARCH_EMEV2)+= smp-emev2.o headsmp-scu.o
>>> platsmp-scu.o
>>>>
>>>>  # PM objects
>>>> diff --git a/arch/arm/mach-shmobile/smp-r9a06g032.c
>>>> b/arch/arm/mach-shmobile/smp-r9a06g032.c
>>>> new file mode 100644
>>>> index 0000000..cd40e6e
>>>> --- /dev/null
>>>> +++ b/arch/arm/mach-shmobile/smp-r9a06g032.c
>>>> @@ -0,0 +1,79 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * R9A06G032 Second CA7 enabler.
>>>> + *
>>>> + * Copyright (C) 2018 Renesas Electronics Europe Limited
>>>> + *
>>>> + * Michel Pollet <michel.pollet@bp.renesas.com>,
>>> <buserror@gmail.com>
>>>> + * Derived from action,s500-smp
>>>> + */
>>>> +
>>>> +#include <linux/io.h>
>>>> +#include <linux/of.h>
>>>> +#include <linux/of_address.h>
>>>> +#include <linux/smp.h>
>>>> +
>>>> +/*
>>>> + * 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.

Actually, this is all already documented in the DT spec and it is
always 2 cells[1]. We should perhaps just remove whatever is
duplicated from the spec.

Rob

[1]
   ``cpu-release-addr``   | SD  | ``<u64>``        The
cpu-release-addr property is required for
                                                   cpu nodes that have
an enable-method property
                                                   value of
``"spin-table"``. The value specifies the
                                                   physical address of
a spin table entry that
                                                   releases a
secondary CPU from its spin loop.