>-----Original Message----- >From: Kevin Hilman [mailto:khilman@xxxxxxxxxxxxxxxxxxx] >Sent: Friday, June 05, 2009 4:54 AM >To: Nayak, Rajendra >Cc: linux-omap@xxxxxxxxxxxxxxx >Subject: Re: [PATCH 05/06] OMAP3: PM: Implement locking for >any scratchpad access > >Rajendra Nayak <rnayak@xxxxxx> writes: > >> This patch implements locking using the semaphore in scratchpad >> memory preventing any concurrent access to scratchpad from OMAP >> and Baseband/Modem processor. >> >> Signed-off-by: Rajendra Nayak <rnayak@xxxxxx> > >Any reason this function has to be written in asm? It's written along >with a bunch of other asm functions that are copied to and executed >from SRAM, but that doesn't appear to be the case here. > >Looks like a simple C function would be clearer here. Kevin, The idea was to atomically read and write into the semaphore memory location in scratchpad using a swp instruction. I am not too sure how to do this in C. regards, Rajendra > >Kevin > >> --- >> arch/arm/mach-omap2/resource34xx.c | 6 +++++- >> arch/arm/mach-omap2/resource34xx.h | 2 ++ >> arch/arm/mach-omap2/sleep34xx.S | 32 >++++++++++++++++++++++++++++++++ >> 3 files changed, 39 insertions(+), 1 deletions(-) >> >> diff --git a/arch/arm/mach-omap2/resource34xx.c >b/arch/arm/mach-omap2/resource34xx.c >> index 82405b6..408d3ab 100644 >> --- a/arch/arm/mach-omap2/resource34xx.c >> +++ b/arch/arm/mach-omap2/resource34xx.c >> @@ -236,6 +236,7 @@ static int program_opp_freq(int res, int >target_level, int current_level) >> int ret = 0, l3_div; >> int *curr_opp; >> >> + lock_scratchpad_sem(); >> if (res == VDD1_OPP) { >> curr_opp = &curr_vdd1_opp; >> clk_set_rate(dpll1_clk, mpu_opps[target_level].rate); >> @@ -253,11 +254,14 @@ static int program_opp_freq(int res, >int target_level, int current_level) >> ret = clk_set_rate(dpll3_clk, >> l3_opps[target_level].rate * l3_div); >> } >> - if (ret) >> + if (ret) { >> + unlock_scratchpad_sem(); >> return current_level; >> + } >> #ifdef CONFIG_PM >> omap3_save_scratchpad_contents(); >> #endif >> + unlock_scratchpad_sem(); >> >> *curr_opp = target_level; >> return target_level; >> diff --git a/arch/arm/mach-omap2/resource34xx.h >b/arch/arm/mach-omap2/resource34xx.h >> index a160665..5b5618a 100644 >> --- a/arch/arm/mach-omap2/resource34xx.h >> +++ b/arch/arm/mach-omap2/resource34xx.h >> @@ -29,6 +29,8 @@ >> #include <mach/omap34xx.h> >> >> extern int sr_voltagescale_vcbypass(u32 t_opp, u32 c_opp, >u8 t_vsel, u8 c_vsel); >> +extern void lock_scratchpad_sem(); >> +extern void unlock_scratchpad_sem(); >> >> /* >> * mpu_latency/core_latency are used to control the cpuidle C state. >> diff --git a/arch/arm/mach-omap2/sleep34xx.S >b/arch/arm/mach-omap2/sleep34xx.S >> index 38aa3fd..aedcf94 100644 >> --- a/arch/arm/mach-omap2/sleep34xx.S >> +++ b/arch/arm/mach-omap2/sleep34xx.S >> @@ -39,6 +39,7 @@ >> #define PM_PREPWSTST_MPU_V OMAP34XX_PRM_REGADDR(MPU_MOD, \ >> OMAP3430_PM_PREPWSTST) >> #define CM_IDLEST1_CORE_V OMAP34XX_CM_REGADDR(CORE_MOD, >CM_IDLEST1) >> +#define SDRC_SCRATCHPAD_SEM_V 0xd800291C >> >> /* >> * This is the physical address of the register as specified >> @@ -62,6 +63,37 @@ >> #define SDRC_DLLA_STATUS_V OMAP34XX_SDRC_REGADDR(SDRC_DLLA_STATUS) >> #define SDRC_DLLA_CTRL_V OMAP34XX_SDRC_REGADDR(SDRC_DLLA_CTRL) >> >> + .text >> +/* Function to aquire the semaphore in scratchpad */ >> +ENTRY(lock_scratchpad_sem) >> + stmfd sp!, {lr} @ save registers on stack >> +wait_sem: >> + mov r0,#1 >> + ldr r1, sdrc_scratchpad_sem >> +wait_loop: >> + ldr r2, [r1] @ load the lock value >> + cmp r2, r0 @ is the lock free ? >> + beq wait_loop @ not free... >> + swp r2, r0, [r1] @ semaphore free so lock it and proceed >> + cmp r2, r0 @ did we succeed ? >> + beq wait_sem @ no - try again >> + ldmfd sp!, {pc} @ restore regs and return >> +sdrc_scratchpad_sem: >> + .word SDRC_SCRATCHPAD_SEM_V >> +ENTRY(lock_scratchpad_sem_sz) >> + .word . - lock_scratchpad_sem >> + >> + .text >> +/* Function to release the scratchpad semaphore */ >> +ENTRY(unlock_scratchpad_sem) >> + stmfd sp!, {lr} @ save registers on stack >> + ldr r3, sdrc_scratchpad_sem >> + mov r2,#0 >> + str r2,[r3] >> + ldmfd sp!, {pc} @ restore regs and return >> +ENTRY(unlock_scratchpad_sem_sz) >> + .word . - unlock_scratchpad_sem >> + >> .text >> /* Function call to get the restore pointer for resume from OFF */ >> ENTRY(get_restore_pointer) >> -- >> 1.5.4.7 >> >> -- >> 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 > >-- 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
