[PATCH 07/10] OMAP3 clock: only unlock SDRC DLL if SDRC clk < 83MHz

Paul Walmsley
2009-05-13T00:09:41Z

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>
---
arch/arm/mach-omap2/clock34xx.c | 10 +++++++++-
arch/arm/mach-omap2/sram34xx.S | 13 +++++++------
arch/arm/plat-omap/include/mach/sram.h | 6 ++++--
arch/arm/plat-omap/sram.c | 7 ++++---
4 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/arch/arm/mach-omap2/clock34xx.c b/arch/arm/mach-omap2/clock34xx.c
index 0a14dca..811360a 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 35131e5..c080c82 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
diff --git a/arch/arm/plat-omap/include/mach/sram.h b/arch/arm/plat-omap/include/mach/sram.h
index ab35d62..dca7c16 100644
--- a/arch/arm/plat-omap/include/mach/sram.h
+++ b/arch/arm/plat-omap/include/mach/sram.h
@@ -23,7 +23,8 @@ extern u32 omap2_set_prcm(u32 dpll_ctrl_val, u32 sdrc_rfr_val, int bypass);

extern u32 omap3_configure_core_dpll(u32 sdrc_rfr_ctrl,
u32 sdrc_actim_ctrla,
- u32 sdrc_actim_ctrlb, u32 m2);
+ u32 sdrc_actim_ctrlb, u32 m2,
+ u32 unlock_dll);

/* Do not use these */
extern void omap1_sram_reprogram_clock(u32 ckctl, u32 dpllctl);
@@ -60,7 +61,8 @@ extern unsigned long omap243x_sram_reprogram_sdrc_sz;

extern u32 omap3_sram_configure_core_dpll(u32 sdrc_rfr_ctrl,
u32 sdrc_actim_ctrla,
- u32 sdrc_actim_ctrlb, u32 m2);
+ u32 sdrc_actim_ctrlb, u32 m2,
+ u32 unlock_dll);
extern unsigned long omap3_sram_configure_core_dpll_sz;

#endif
diff --git a/arch/arm/plat-omap/sram.c b/arch/arm/plat-omap/sram.c
index 3835338..876f5a7 100644
--- a/arch/arm/plat-omap/sram.c
+++ b/arch/arm/plat-omap/sram.c
@@ -365,16 +365,17 @@ static inline int omap243x_sram_init(void)
static u32 (*_omap3_sram_configure_core_dpll)(u32 sdrc_rfr_ctrl,
u32 sdrc_actim_ctrla,
u32 sdrc_actim_ctrlb,
- u32 m2);
+ u32 m2, u32 unlock_dll);
u32 omap3_configure_core_dpll(u32 sdrc_rfr_ctrl, u32 sdrc_actim_ctrla,
- u32 sdrc_actim_ctrlb, u32 m2)
+ u32 sdrc_actim_ctrlb, u32 m2, u32 unlock_dll)
{
if (!_omap3_sram_configure_core_dpll)
omap_sram_error();

return _omap3_sram_configure_core_dpll(sdrc_rfr_ctrl,
sdrc_actim_ctrla,
- sdrc_actim_ctrlb, m2);
+ sdrc_actim_ctrlb, m2,
+ unlock_dll);
}

/* REVISIT: Should this be same as omap34xx_sram_init() after off-idle? */