Hi Santosh,
Thanks for looking at this series.
On Fri, Jul 08, 2011 at 02:45:43AM +0100, Santosh Shilimkar wrote:
On 7/7/2011 8:50 AM, Lorenzo Pieralisi wrote:
In order to define a common idle interface for the kernel to enter low power modes, this patch provides include files and code that manages OS calls for low power entry and exit.
[....]
diff --git a/arch/arm/kernel/sr_entry.S b/arch/arm/kernel/sr_entry.S new file mode 100644 index 0000000..4fa9bef --- /dev/null +++ b/arch/arm/kernel/sr_entry.S @@ -0,0 +1,213 @@ +/*
- Copyright (c) 2008-2011 ARM Ltd
- Author(s): Jon Callan, Lorenzo Pieralisi
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License version 2 as
- published by the Free Software Foundation.
- */
+#include<linux/linkage.h> +#include<generated/asm-offsets.h> +#include<asm/thread_info.h> +#include<asm/memory.h> +#include<asm/ptrace.h> +#include<asm/glue-proc.h> +#include<asm/assembler.h> +#include<asm-generic/errno-base.h> +#include<mach/entry-macro.S>
- .text
+ENTRY(default_sleep)
- b out @ BTAC allocates branch and enters loop mode
+idle: @ power down is entered with GIC CPU IF still on which
- dsb @ might get wfi instruction to complete before the
- wfi @ CPU is shut down -- infinite loop
+out:
b idle+ENDPROC(default_sleep)
Q: What happens for some reason CPU didn't hit targeted state in IDLE. Does CPU keep looping here forever.
On OMAP4, we need to issue additional interconnect barrier before WFI. How can we make provision for the same
That's why I added a function pointer, (*sr_sleep) as a way to override the default loop behaviour which is there to prevent the cpu to exit wfi after a point of no return (GIC CPU IF is still on). It is just a tentative solution, so please feel free to comment on this. If you pop out from (*sr_sleep) the current code jumps through cpu_reset and emulates a reset, which may not be optimal. You might also want to execute from SRAM. I have to cater for that.
Again, comments more than welcome.
Lorenzo