• Dave Gerlach's avatar
    memory: ti-emif-sram: introduce relocatable suspend/resume handlers · 8428e5ad
    Dave Gerlach authored
    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.
    Acked-by: default avatarTony Lindgren <tony@atomide.com>
    Acked-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
    Signed-off-by: default avatarDave Gerlach <d-gerlach@ti.com>
    Signed-off-by: default avatarSantosh Shilimkar <santosh.shilimkar@oracle.com>
Makefile.asm-offsets 233 Bytes