[PATCH] pm: at91: pm_slowclock: improve reliability of suspend/resume

[Sylvain Rochet]

Assume USB PLL and PLL B are already stopped before entering sleep mode,
print a warning if this isn't the case.

Removed timeout on XTAL, PLL lock and Master Clock Ready, hang if
something went wrong instead of continuing in unknown condition. There
is not much we can do if a PLL lock never ends, we are running in SRAM
and we will not be able to connect back the sdram or ddram in order to
be able to fire up a message or just panic.

As a bonus, not decounting the timeout register in slow clock mode
reduce cumulated suspend time and resume time from ~17ms to ~15ms.

Signed-off-by: Sylvain Rochet <sylvain.rochet at finsecur.com>
---
 arch/arm/mach-at91/pm.c           | 12 ++++++++
 arch/arm/mach-at91/pm_slowclock.S | 62 ++-------------------------------------
 2 files changed, 15 insertions(+), 59 deletions(-)

diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 9b15169..1cfd6e9 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -98,6 +98,18 @@ static int at91_pm_verify_clocks(void)
 		}
 	}
 
+	/* Drivers should have previously suspended USB PLL */
+	if (at91_pmc_read(AT91_CKGR_UCKR) & AT91_PMC_UPLLEN) {
+		pr_err("AT91: PM - Suspend-to-RAM with USB PLL running\n");
+		return 0;
+	}
+
+	/* Drivers should have previously suspended PLL B */
+	if (at91_pmc_read(AT91_PMC_SR) & AT91_PMC_LOCKB) {
+		pr_err("AT91: PM - Suspend-to-RAM with PLL B running\n");
+		return 0;
+	}
+
 	return 1;
 }
 
diff --git a/arch/arm/mach-at91/pm_slowclock.S b/arch/arm/mach-at91/pm_slowclock.S
index 2001877..75d8b19 100644
--- a/arch/arm/mach-at91/pm_slowclock.S
+++ b/arch/arm/mach-at91/pm_slowclock.S
@@ -34,11 +34,6 @@
  */
 #undef SLOWDOWN_MASTER_CLOCK
 
-#define MCKRDY_TIMEOUT		1000
-#define MOSCRDY_TIMEOUT 	1000
-#define PLLALOCK_TIMEOUT	1000
-#define PLLBLOCK_TIMEOUT	1000
-
 pmc	.req	r0
 sdramc	.req	r1
 ramc1	.req	r2
@@ -50,56 +45,27 @@ tmp2	.req	r5
  * Wait until master clock is ready (after switching master clock source)
  */
 	.macro wait_mckrdy
-	mov	tmp2, #MCKRDY_TIMEOUT
-1:	sub	tmp2, tmp2, #1
-	cmp	tmp2, #0
-	beq	2f
-	ldr	tmp1, [pmc, #AT91_PMC_SR]
+1:	ldr	tmp1, [pmc, #AT91_PMC_SR]
 	tst	tmp1, #AT91_PMC_MCKRDY
 	beq	1b
-2:
 	.endm
 
 /*
  * Wait until master oscillator has stabilized.
  */
 	.macro wait_moscrdy
-	mov	tmp2, #MOSCRDY_TIMEOUT
-1:	sub	tmp2, tmp2, #1
-	cmp	tmp2, #0
-	beq	2f
-	ldr	tmp1, [pmc, #AT91_PMC_SR]
+1:	ldr	tmp1, [pmc, #AT91_PMC_SR]
 	tst	tmp1, #AT91_PMC_MOSCS
 	beq	1b
-2:
 	.endm
 
 /*
  * Wait until PLLA has locked.
  */
 	.macro wait_pllalock
-	mov	tmp2, #PLLALOCK_TIMEOUT
-1:	sub	tmp2, tmp2, #1
-	cmp	tmp2, #0
-	beq	2f
-	ldr	tmp1, [pmc, #AT91_PMC_SR]
+1:	ldr	tmp1, [pmc, #AT91_PMC_SR]
 	tst	tmp1, #AT91_PMC_LOCKA
 	beq	1b
-2:
-	.endm
-
-/*
- * Wait until PLLB has locked.
- */
-	.macro wait_pllblock
-	mov	tmp2, #PLLBLOCK_TIMEOUT
-1:	sub	tmp2, tmp2, #1
-	cmp	tmp2, #0
-	beq	2f
-	ldr	tmp1, [pmc, #AT91_PMC_SR]
-	tst	tmp1, #AT91_PMC_LOCKB
-	beq	1b
-2:
 	.endm
 
 	.text
@@ -207,13 +173,6 @@ sdr_sr_done:
 	orr	tmp1, tmp1, #(1 << 29)		/* bit 29 always set */
 	str	tmp1, [pmc, #AT91_CKGR_PLLAR]
 
-	/* Save PLLB setting and disable it */
-	ldr	tmp1, [pmc, #AT91_CKGR_PLLBR]
-	str	tmp1, .saved_pllbr
-
-	mov	tmp1, #AT91_PMC_PLLCOUNT
-	str	tmp1, [pmc, #AT91_CKGR_PLLBR]
-
 	/* Turn off the main oscillator */
 	ldr	tmp1, [pmc, #AT91_CKGR_MOR]
 	bic	tmp1, tmp1, #AT91_PMC_MOSCEN
@@ -229,18 +188,6 @@ sdr_sr_done:
 
 	wait_moscrdy
 
-	/* Restore PLLB setting */
-	ldr	tmp1, .saved_pllbr
-	str	tmp1, [pmc, #AT91_CKGR_PLLBR]
-
-	tst	tmp1, #(AT91_PMC_MUL &  0xff0000)
-	bne	1f
-	tst	tmp1, #(AT91_PMC_MUL & ~0xff0000)
-	beq	2f
-1:
-	wait_pllblock
-2:
-
 	/* Restore PLLA setting */
 	ldr	tmp1, .saved_pllar
 	str	tmp1, [pmc, #AT91_CKGR_PLLAR]
@@ -319,9 +266,6 @@ ram_restored:
 .saved_pllar:
 	.word 0
 
-.saved_pllbr:
-	.word 0
-
 .saved_sam9_lpr:
 	.word 0
 
-- 
2.1.4