[PATCH v5 2/7] OMAP3: PM: Erratum i581 support: dll kick strategy

[Nishanth Menon <nm@ti.com>]

From: Peter 'p2' De Schrijver <peter.de-schrijver@nokia.com>

Erratum i581 impacts OMAP3 platforms.
PRCM DPLL control FSM removes SDRC_IDLEREQ before DPLL3 locks causing
the DPLL not to be locked at times.

IMPORTANT:
*) This is not a complete workaround implementation as recommended
by the silicon erratum. This is a support logic for detecting lockups and
attempting to recover where possible and is known to provide stability
in multiple platforms.
*) This code is mostly important for inactive and retention. The ROM code
waits for the maximum DLL lock time when resuming from off mode. So for
off mode this code isn't really needed.
*) counters are introduced here for eventual export to userspace once the
cleanups are completed.

This should eventually get refactored as part of cleanups to sleep34xx.S

Cc: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Tony Lindgren <tony@atomide.com>

Signed-off-by: Peter 'p2' De Schrijver <peter.de-schrijver@nokia.com>
---
v3: additional comment on the TODO of exposing the counters eventually
    after the sram34xx.S cleanups are completed.
v2: https://patchwork.kernel.org/patch/365252/
	typo correction- erratum, support, added comment from Peter from the
	thread to commit message
v1: http://marc.info/?l=linux-omap&m=129013172525234&w=2

 arch/arm/mach-omap2/sleep34xx.S |   55 +++++++++++++++++++++++++++++++++++---
 1 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-omap2/sleep34xx.S b/arch/arm/mach-omap2/sleep34xx.S
index aa43da5..24ecb0a 100644
--- a/arch/arm/mach-omap2/sleep34xx.S
+++ b/arch/arm/mach-omap2/sleep34xx.S
@@ -42,6 +42,7 @@
 				OMAP3430_PM_PREPWSTST)
 #define PM_PWSTCTRL_MPU_P	OMAP3430_PRM_BASE + MPU_MOD + OMAP2_PM_PWSTCTRL
 #define CM_IDLEST1_CORE_V	OMAP34XX_CM_REGADDR(CORE_MOD, CM_IDLEST1)
+#define CM_IDLEST_CKGEN_V	OMAP34XX_CM_REGADDR(PLL_MOD, CM_IDLEST)
 #define SRAM_BASE_P		0x40200000
 #define CONTROL_STAT		0x480022F0
 #define SCRATCHPAD_MEM_OFFS	0x310 /* Move this as correct place is
@@ -555,31 +556,67 @@ skip_l2_inval:
 
 /* Make sure SDRC accesses are ok */
 wait_sdrc_ok:
+
+/* DPLL3 must be locked before accessing the SDRC. Maybe the HW ensures this. */
+	ldr	r4, cm_idlest_ckgen
+wait_dpll3_lock:
+	ldr	r5, [r4]
+	tst	r5, #1
+	beq	wait_dpll3_lock
+
         ldr     r4, cm_idlest1_core
+wait_sdrc_ready:
         ldr     r5, [r4]
-        and     r5, r5, #0x2
-        cmp     r5, #0
-        bne     wait_sdrc_ok
+        tst     r5, #0x2
+        bne     wait_sdrc_ready
+	/* allow DLL powerdown upon hw idle req */
         ldr     r4, sdrc_power
         ldr     r5, [r4]
         bic     r5, r5, #0x40
         str     r5, [r4]
-wait_dll_lock:
+is_dll_in_lock_mode:
+
         /* Is dll in lock mode? */
         ldr     r4, sdrc_dlla_ctrl
         ldr     r5, [r4]
         tst     r5, #0x4
         bxne    lr
         /* wait till dll locks */
-        ldr     r4, sdrc_dlla_status
+wait_dll_lock_timed:
+	ldr	r4, wait_dll_lock_counter
+	add	r4, r4, #1
+	str	r4, wait_dll_lock_counter
+	ldr	r4, sdrc_dlla_status
+        mov	r6, #8		/* Wait 20uS for lock */
+wait_dll_lock:
+	subs	r6, r6, #0x1
+	beq	kick_dll
         ldr     r5, [r4]
         and     r5, r5, #0x4
         cmp     r5, #0x4
         bne     wait_dll_lock
         bx      lr
 
+	/* disable/reenable DLL if not locked */
+kick_dll:
+	ldr	r4, sdrc_dlla_ctrl
+	ldr	r5, [r4]
+	mov	r6, r5
+	bic	r6, #(1<<3)	/* disable dll */
+	str	r6, [r4]
+	dsb
+	orr	r6, r6, #(1<<3)	/* enable dll */
+	str	r6, [r4]
+	dsb
+	ldr	r4, kick_counter
+	add	r4, r4, #1
+	str	r4, kick_counter
+	b	wait_dll_lock_timed
+
 cm_idlest1_core:
 	.word	CM_IDLEST1_CORE_V
+cm_idlest_ckgen:
+	.word	CM_IDLEST_CKGEN_V
 sdrc_dlla_status:
 	.word	SDRC_DLLA_STATUS_V
 sdrc_dlla_ctrl:
@@ -616,5 +653,13 @@ control_stat:
 	.word	CONTROL_STAT
 kernel_flush:
 	.word v7_flush_dcache_all
+	/*
+	 * When exporting to userspace while the counters are in SRAM,
+	 * these 2 words need to be at the end to facilitate retrival!
+	 */
+kick_counter:
+	.word	0
+wait_dll_lock_counter:
+	.word	0
 ENTRY(omap34xx_cpu_suspend_sz)
 	.word	. - omap34xx_cpu_suspend
-- 
1.6.3.3