Re: [PATCH v5 2/2] memory: ti-emif-sram: introduce relocatable suspend/resume handlers

[Santosh Shilimkar]

Hi Russell,

On 10/13/2017 1:59 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 processing
> emif-asm-offsets.c into assembly code and then extracting the relevant
> data as is done for the generated platform asm-offsets.h files.
>
> Signed-off-by: Dave Gerlach <d-gerlach@xxxxxx>
> ---
> v4->v5:
> * Simplify Makefile to generate include/generated/ti-emif-asm-offsets.h
If you are happy with this version from Dave, can I get your ack please?
I can add this to the driver-soc then.

Regards,
Santosh