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| author | Paul Walmsley <paul@pwsan.com> | 2009-05-13 03:26:32 +0400 |
|---|---|---|
| committer | paul <paul@twilight.(none)> | 2009-05-13 03:27:10 +0400 |
| commit | 4519c2bf433b97d091635eb51e4ba8ffa1c84d62 (patch) | |
| tree | 0b36fc5e39c6a29005783c74f727c953c75e2198 /arch/arm/mach-omap2 | |
| parent | b2abb271a5705bc80478e79d95fc9f3babc2605c (diff) | |
| download | linux-4519c2bf433b97d091635eb51e4ba8ffa1c84d62.tar.xz | |
OMAP3 clock: only unlock SDRC DLL if SDRC clk < 83MHz
According to the 34xx TRM Rev. K section 11.2.4.4.11.1 "Purpose of the
DLL/CDL Module," the SDRC delay-locked-loop can be locked at any SDRC
clock frequency from 83MHz to 166MHz. CDP code unconditionally
unlocked the DLL whenever shifting to a lower SDRC speed, but this
seems unnecessary and error-prone, as the DLL is no longer able to
compensate for process, voltage, and temperature variations. Instead,
only unlock the DLL when the SDRC clock rate would be less than 83MHz.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Diffstat (limited to 'arch/arm/mach-omap2')
| -rw-r--r-- | arch/arm/mach-omap2/clock34xx.c | 10 | ||||
| -rw-r--r-- | arch/arm/mach-omap2/sram34xx.S | 13 |
2 files changed, 16 insertions, 7 deletions
diff --git a/arch/arm/mach-omap2/clock34xx.c b/arch/arm/mach-omap2/clock34xx.c index 0a14dca31e30..811360af60dc 100644 --- a/arch/arm/mach-omap2/clock34xx.c +++ b/arch/arm/mach-omap2/clock34xx.c @@ -281,6 +281,8 @@ static struct omap_clk omap34xx_clks[] = { #define MAX_DPLL_WAIT_TRIES 1000000 +#define MIN_SDRC_DLL_LOCK_FREQ 83000000 + /** * omap3_dpll_recalc - recalculate DPLL rate * @clk: DPLL struct clk @@ -703,6 +705,7 @@ static int omap3_dpll4_set_rate(struct clk *clk, unsigned long rate) static int omap3_core_dpll_m2_set_rate(struct clk *clk, unsigned long rate) { u32 new_div = 0; + u32 unlock_dll = 0; unsigned long validrate, sdrcrate; struct omap_sdrc_params *sp; @@ -729,6 +732,11 @@ static int omap3_core_dpll_m2_set_rate(struct clk *clk, unsigned long rate) if (!sp) return -EINVAL; + if (sdrcrate < MIN_SDRC_DLL_LOCK_FREQ) { + pr_debug("clock: will unlock SDRC DLL\n"); + unlock_dll = 1; + } + pr_info("clock: changing CORE DPLL rate from %lu to %lu\n", clk->rate, validrate); pr_info("clock: SDRC timing params used: %08x %08x %08x\n", @@ -739,7 +747,7 @@ static int omap3_core_dpll_m2_set_rate(struct clk *clk, unsigned long rate) /* REVISIT: Add SDRC_MR changing to this code also */ omap3_configure_core_dpll(sp->rfr_ctrl, sp->actim_ctrla, - sp->actim_ctrlb, new_div); + sp->actim_ctrlb, new_div, unlock_dll); return 0; } diff --git a/arch/arm/mach-omap2/sram34xx.S b/arch/arm/mach-omap2/sram34xx.S index 35131e5bc7d1..c080c82521e1 100644 --- a/arch/arm/mach-omap2/sram34xx.S +++ b/arch/arm/mach-omap2/sram34xx.S @@ -40,22 +40,23 @@ /* * Change frequency of core dpll * r0 = sdrc_rfr_ctrl r1 = sdrc_actim_ctrla r2 = sdrc_actim_ctrlb r3 = M2 + * r4 = Unlock SDRC DLL? (1 = yes, 0 = no) -- only unlock DLL for + * SDRC rates < 83MHz */ ENTRY(omap3_sram_configure_core_dpll) stmfd sp!, {r1-r12, lr} @ store regs to stack + ldr r4, [sp, #52] @ pull extra args off the stack dsb @ flush buffered writes to interconnect cmp r3, #0x2 blne configure_sdrc - cmp r3, #0x2 + cmp r4, #0x1 + bleq unlock_dll blne lock_dll - cmp r3, #0x1 - blne unlock_dll bl sdram_in_selfrefresh @ put the SDRAM in self refresh bl configure_core_dpll bl enable_sdrc - cmp r3, #0x1 - blne wait_dll_unlock - cmp r3, #0x2 + cmp r4, #0x1 + bleq wait_dll_unlock blne wait_dll_lock cmp r3, #0x1 blne configure_sdrc |