Re: [PATCH v3 2/2] memory: ti-emif-sram: introduce relocatable suspend/resume handlers

[Santosh Shilimkar]

On 7/26/2017 9:54 AM, Santosh Shilimkar wrote:
> On 7/24/2017 2:24 PM, Dave Gerlach wrote:
> > Certain SoCs like Texas Instruments AM335x and AM437x require parts
> > of the EMIF PM code to run late in the suspend sequence from SRAM,
> > such as saving and restoring the EMIF context and placing the memory
> > into self-refresh.
> >
> > One requirement for these SoCs to suspend and enter its lowest power
> > mode, called DeepSleep0, is that the PER power domain must be shut off.
> > Because the EMIF (DDR Controller) resides within this power domain, it
> > will lose context during a suspend operation, so we must save it so we
> > can restore once we resume. However, we cannot execute this code from
> > external memory, as it is not available at this point, so the code must
> > be executed late in the suspend path from SRAM.
> >
> > This patch introduces a ti-emif-sram driver that includes several
> > functions written in ARM ASM that are relocatable so the PM SRAM
> > code can use them. It also allocates a region of writable SRAM to
> > be used by the code running in the executable region of SRAM to save
> > and restore the EMIF context. It can export a table containing the
> > absolute addresses of the available PM functions so that other SRAM
> > code can branch to them. This code is required for suspend/resume on
> > AM335x and AM437x to work.
> >
> > In addition to this, to be able to share data structures between C and
> > the ti-emif-sram-pm assembly code, we can automatically generate all of
> > the C struct member offsets and sizes as macros by making use of the ARM
> > asm-offsets file. In the same header that we define our data structures
> > in we also define all the macros in an inline function and by adding a
> > call to this in the asm_offsets file all macros are properly generated
> > and available to the assembly code without cluttering up the asm-offsets
> > file.
> >
> > Signed-off-by: Dave Gerlach <d-gerlach@xxxxxx>
> > ---
[...]

> >   arch/arm/kernel/asm-offsets.c    |   4 +
> >   drivers/memory/Kconfig           |  10 ++
> >   drivers/memory/Makefile          |   4 +
> >   drivers/memory/emif.h            |  17 ++
> >   drivers/memory/ti-emif-pm.c      | 339 
> > +++++++++++++++++++++++++++++++++++++++
> >   drivers/memory/ti-emif-sram-pm.S | 334 
> > ++++++++++++++++++++++++++++++++++++++
> >   include/linux/ti-emif-sram.h     | 147 +++++++++++++++++
> >   7 files changed, 855 insertions(+)
> >   create mode 100644 drivers/memory/ti-emif-pm.c
> >   create mode 100644 drivers/memory/ti-emif-sram-pm.S
> >   create mode 100644 include/linux/ti-emif-sram.h
> I will need RMKs blessing since he reviewed the ASM code.
>
> Also need work out how to line this up. Typically I use to get
> driver/memory patches via Greg's driver-core but this is more
> PM code than memory driver and very SOC specific.
>
> Hi Arnd/Olof,
> Will you be ok to pull this via arm-soc ? There is also follow
> up platform PM code and DTS series which will make use of this.
Looks like I missed to copy Olof. Let me know guys if you are
ok to pull this into your driver-soc given the dependencies.

Regards
Santosh