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| author | Paul Walmsley <paul@pwsan.com> | 2009-05-12 17:26:32 -0600 |
|---|---|---|
| committer | paul <paul@twilight.(none)> | 2009-05-12 17:27:10 -0600 |
| commit | 4519c2bf433b97d091635eb51e4ba8ffa1c84d62 (patch) | |
| tree | 0b36fc5e39c6a29005783c74f727c953c75e2198 /arch/arm/mach-omap2/sram34xx.S | |
| parent | b2abb271a5705bc80478e79d95fc9f3babc2605c (diff) | |
| download | lwn-4519c2bf433b97d091635eb51e4ba8ffa1c84d62.tar.gz lwn-4519c2bf433b97d091635eb51e4ba8ffa1c84d62.zip | |
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/sram34xx.S')
| -rw-r--r-- | arch/arm/mach-omap2/sram34xx.S | 13 |
1 files changed, 7 insertions, 6 deletions
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 |