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SubjectRe: [PATCH v3 2/2] memory: ti-emif-sram: introduce relocatable suspend/resume handlers
On 08/01/2017 01:08 PM, Santosh Shilimkar wrote:
> 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 <>
>>> ---
> [...]
>>> 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.

Any additional comments here? I believe I have addressed everything from v2 so
hopefully this is acceptable now.


> Regards
> Santosh

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