On Thu, Aug 8, 2013 at 8:22 AM, Santosh Shilimkar <santosh.shilimkar@xxxxxx> wrote: > On Thursday 08 August 2013 11:16 AM, Russ Dill wrote: >> On Thu, Aug 8, 2013 at 7:50 AM, Santosh Shilimkar >> <santosh.shilimkar@xxxxxx> wrote: >>> On Tuesday 06 August 2013 01:49 PM, Dave Gerlach wrote: >>>> From: Vaibhav Bedia <vaibhav.bedia@xxxxxx> >>>> >>>> In preparation for suspend-resume support for AM33XX, add >>>> the assembly file with the code which is copied to internal >>>> memory (OCMC RAM) during bootup and runs from there. >>>> >>>> As part of the low power entry (DeepSleep0 mode in AM33XX TRM), >>>> the code running from OCMC RAM does the following >>>> 1. Stores the EMIF configuration >>>> 2. Puts external memory in self-refresh >>>> 3. Disables EMIF clock >>>> 4. Executes WFI after writing to MPU_CLKCTRL register. >>>> >>>> If no interrupts have come, WFI execution on MPU gets registered >>>> as an interrupt with the WKUP-M3. WKUP-M3 takes care of disabling >>>> some clocks which MPU should not (L3, L4, OCMC RAM etc) and takes >>>> care of clockdomain and powerdomain transitions as part of the >>>> DeepSleep0 mode entry. >>>> >>>> In case a late interrupt comes in, WFI ends up as a NOP and MPU >>>> continues execution from internal memory. The 'abort path' code >>>> undoes whatever was done as part of the low power entry and indicates >>>> a suspend failure by passing a non-zero value to the cpu_resume routine. >>>> >>>> The 'resume path' code is similar to the 'abort path' with the key >>>> difference of MMU being enabled in the 'abort path' but being >>>> disabled in the 'resume path' due to MPU getting powered off. >>>> >>>> Signed-off-by: Vaibhav Bedia <vaibhav.bedia@xxxxxx> >>>> Signed-off-by: Dave Gerlach <d-gerlach@xxxxxx> >>>> Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxx> >>>> Cc: Kevin Hilman <khilman@xxxxxxxxxx> >>>> --- >>>> arch/arm/mach-omap2/sleep33xx.S | 350 +++++++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 350 insertions(+) >>>> create mode 100644 arch/arm/mach-omap2/sleep33xx.S >>>> >>>> diff --git a/arch/arm/mach-omap2/sleep33xx.S b/arch/arm/mach-omap2/sleep33xx.S >>>> new file mode 100644 >>>> index 0000000..834c7d4 >>>> --- /dev/null >>>> +++ b/arch/arm/mach-omap2/sleep33xx.S >>>> @@ -0,0 +1,350 @@ >>>> +/* >>>> + * Low level suspend code for AM33XX SoCs >>>> + * >>>> + * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/ >>>> + * Vaibhav Bedia <vaibhav.bedia@xxxxxx> >>>> + * >>>> + * This program is free software; you can redistribute it and/or >>>> + * modify it under the terms of the GNU General Public License as >>>> + * published by the Free Software Foundation version 2. >>>> + * >>>> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any >>>> + * kind, whether express or implied; without even the implied warranty >>>> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >>>> + * GNU General Public License for more details. >>>> + */ >>>> + >>>> +#include <linux/linkage.h> >>>> +#include <linux/ti_emif.h> >>>> +#include <asm/memory.h> >>>> +#include <asm/assembler.h> >>>> + >>>> +#include "cm33xx.h" >>>> +#include "pm33xx.h" >>>> +#include "prm33xx.h" >>>> + >>>> + .text >>>> + .align 3 >>>> + >>>> +/* >>>> + * This routine is executed from internal RAM and expects some >>>> + * parameters to be passed in r0 _strictly_ in following order: >>>> + * 1) emif_addr_virt - ioremapped EMIF address >>>> + * 2) mem_type - 2 -> DDR2, 3-> DDR3 >>>> + * 3) dram_sync_word - uncached word in SDRAM >>>> + * >>>> + * The code loads these values taking r0 value as reference to >>>> + * the array in registers starting from r0, i.e emif_addr_virt >>>> + * goes to r1, mem_type goes to r2 and and so on. These are >>>> + * then saved into memory locations before proceeding with the >>>> + * sleep sequence and hence registers r0, r1 etc can still be >>>> + * used in the rest of the sleep code. >>>> + */ >>>> + >>>> +ENTRY(am33xx_do_wfi) >>>> + stmfd sp!, {r4 - r11, lr} @ save registers on stack >>>> + >>>> + ldm r0, {r1-r3} @ gather values passed >>>> + >>>> + /* Save the values passed */ >>>> + str r1, emif_addr_virt >>>> + str r2, mem_type >>>> + str r3, dram_sync_word >>> >>> None of this parameter are going to change for every suspend entry and >>> exit so saving them once and accessing them should be fine. Just >>> create a structure with above, save them in init from C code and >>> then access that structure where you need to. >> >> It isn't possible to do so since the structure would be in SDRAM and >> at resume time, we don't have access to SDRAM. Additionally, I'd like >> to expand the mem_type parameter to a bit field in the future to allow >> this code path to be shared with CPU idle. >> > You can copy the structure in SRAM. So how does memtype need > changes for CPUIDLE ? You'd have to reserve the address and have a symbol exported for it, then after pushing everything to SRAM, you'd have to calculate the pushed address of the reserved space, then do a memcpy. It'd be a bit convoluted. Passing the address to the struct into tho wfi function is really easy and a pretty common thing to do. For cpuidle, i'd probably change it to a flags field instead of just memtype. For instance ddr2 would be (1 << 0), and ddr3 would (1 << 1). Other flags could then be added, such as whether or not to notify the M3 at WFI time. > I have several comments on this patch so I assume you are > going to address them then. > > Regards, > Santosh > > -- 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
