Tony,
On 07/15/2014 01:38 AM, Tony Lindgren wrote:
* Dave Gerlach <d-gerlach@xxxxxx> [140714 10:44]:
On 07/14/2014 06:12 AM, Tony Lindgren wrote:
* Dave Gerlach <d-gerlach@xxxxxx> [140710 19:59]:
OMAP4 and AM33XX share the same EMIF controller IP. Although there
are significant differences in the IP integration due to which
AM33XX can't reuse the EMIF driver DVFS similar to OMAP4,
it can definitely benefit by reusing the EMIF related macros
defined in drivers/memory/emif.h.
In the current OMAP PM framework the PM code resides under
arch/arm/mach-omap2/. To enable reuse of the register defines move
the register defines in the emif header file to include/linux so that
both the EMIF driver and the AM33XX PM code can benefit.
Signed-off-by: Dave Gerlach <d-gerlach@xxxxxx>
Reviewed-by: Russ Dill <russ.dill@xxxxxx>
Acked-by: Santosh Shililmar <santosh.shilimkar@xxxxxx>
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
v3->v4:
patch unchanged from original:
http://www.spinics.net/lists/linux-omap/msg95314.html
drivers/memory/emif.h | 543 +---------------------------------------------
include/linux/ti_emif.h | 558 ++++++++++++++++++++++++++++++++++++++++++++++++
So far we've seen that exposing hardware registers like this
will lead into various drivers misusing them. I think a better
solution is to implement few targeted functions that allow
sharing code between the platform idle code and memory driver.
Maybe you can have the shared functions in in something like
drivers/memory/ti-emif.c that's always built in? The idle
code won't need any of that early on.
Well the reason it was done this way was to utilize all of the addresses of
EMIF register in the ASM sleep code to do relative addressing from the EMIF
base address. The ASM sleep code (patch 9) needs to save and restore emif
context and set and unset self refresh in emif. The issues will come from
the ASM being copied to and running from SRAM without the ability to access
code in DDR (because we are shutting the EMIF off), so we would need to copy
these functions as well and have to worry about any issues we introduce by
relocating c code. Is it worth the added maintenance burden?
Ah right it needs to run in SRAM. There were some relocatable
c code patches posted a while back, so it might be worth
revisiting that.
I think it can also be done with assembly with something like
this:
1. Make am335x idle code depends on TI_EMIF && WKUP_M3_RPROC
2. Add the memory save and restore assembly functions into
drivers/memory/ti-emif-sram.S
3. Allocate the SRAM preferrably with drivers/misc/sram.c
instead of the legacy mach-omap2/sram.c
This I can do, I will just need to make a change somewhere to make generic sram
driver provide sram allocations marked for exec.
4. Map the idle assembly code and EMIF save and restore
functions into SRAM
5. Call the EMIF save and restore functions from the idle
assembly code at the SRAM locations and pass the save and
restore area in a register
So basically we need to figure out a generic way to do driver
hooks in the PM idle code even very late and early in the
assembly code so we can keep most of the code in drivers.
Eventually also the idle assembly code should be in the drivers
too..
I did not consider this earlier but the cpuidle code will use the same path in
the assembly code. The cpuidle configures the suspend path to make the emif
actions optional (save and restore with shut off, and self refresh), so a
generic solution probably isn't possible here as we (will) need a certain level
of granularity of control over the emif actions, and that will be difficult to
maintain while keeping the pm functionality out of the EMIF code.
Regards,
Dave
Regards,
Tony
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
