[PATCH 1/1] ARM: OMAP2+: Fix omap3 off idle power consumption creeping up

[Tony Lindgren]

* Tony Lindgren <tony at atomide.com> [150421 09:24]:
> If we use a combination of VMODE and I2C4 for retention modes,
> eventually the off idle power consumption will creep up by about
> 23mW, even during off mode with I2C4 always staying enabled.
> 
> Looks like the only way to fix the extra power consumption is to
> disable I2C4 usage by setting SEL_VMODE for both off idle and
> retention idle. Let's also update the comments accordingly.

Thanks Nishanth for pointing me to the related SmartReflex I2C4
erratum. No need to disable I2C4 with the SREN workaround :)

Better patch below, presumably this only affects omap3?

Regards,

Tony

8< ------------------------------
From: Tony Lindgren <tony at atomide.com>
Date: Tue, 21 Apr 2015 14:31:23 -0700
Subject: [PATCH] ARM: OMAP2+: Fix omap3 off idle power consumption creeping up

If we use a combination of VMODE and I2C4 for retention modes,
eventually the off idle power consumption will creep up by about
23mW, even during off mode with I2C4 always staying enabled.

Turns out this is because of erratum 2.11 "Extra Power Consumed
When Repeated Start Operation Mode Is Enabled on I2C Interface
Dedicated for Smart Reflex (I2C4)" as pointed out by Nishanth
Menon <nm at ti.com>.

Let's fix the issue by adding i2c_cfg_clear_mask for the bits
to clear when initializing the I2C4 adapter so we can clear
SREN bit that drives the I2C4 lines low otherwise when there
is no traffic.

Fixes: 3b8c4ebb7630 ("ARM: OMAP3: Fix idle mode signaling for
sys_clkreq and sys_off_mode")
Cc: Kevin Hilman <khilman at kernel.org>
Cc: Nishanth Menon <nm at ti.com>
Cc: Tero Kristo <t-kristo at ti.com>
Signed-off-by: Tony Lindgren <tony at atomide.com>

--- a/arch/arm/mach-omap2/prm-regbits-34xx.h
+++ b/arch/arm/mach-omap2/prm-regbits-34xx.h
@@ -112,6 +112,7 @@
 #define OMAP3430_VC_CMD_ONLP_SHIFT			16
 #define OMAP3430_VC_CMD_RET_SHIFT			8
 #define OMAP3430_VC_CMD_OFF_SHIFT			0
+#define OMAP3430_SREN_MASK				(1 << 4)
 #define OMAP3430_HSEN_MASK				(1 << 3)
 #define OMAP3430_MCODE_MASK				(0x7 << 0)
 #define OMAP3430_VALID_MASK				(1 << 24)
--- a/arch/arm/mach-omap2/vc.c
+++ b/arch/arm/mach-omap2/vc.c
@@ -316,7 +316,8 @@ static void __init omap3_vc_init_pmic_signaling(struct voltagedomain *voltdm)
 	 * idle. And we can also scale voltages to zero for off-idle.
 	 * Note that no actual voltage scaling during off-idle will
 	 * happen unless the board specific twl4030 PMIC scripts are
-	 * loaded.
+	 * loaded. See also omap_vc_i2c_init for comments regarding
+	 * erratum 2.11.
 	 */
 	val = voltdm->read(OMAP3_PRM_VOLTCTRL_OFFSET);
 	if (!(val & OMAP3430_PRM_VOLTCTRL_SEL_OFF)) {
@@ -704,9 +705,16 @@ static void __init omap_vc_i2c_init(struct voltagedomain *voltdm)
 		return;
 	}
 
+	/*
+	 * Note that for omap3 OMAP3430_SREN_MASK clears SREN to work around
+	 * erratum 2.11 "Extra Power Consumed When Repeated Start Operation
+	 * Mode Is Enabled on I2C Interface Dedicated for Smart Reflex (I2C4)".
+	 * Otherwise I2C4 eventually leads into about 23mW extran power being
+	 * consumed even during off idle using VMODE.
+	 */
 	i2c_high_speed = voltdm->pmic->i2c_high_speed;
 	if (i2c_high_speed)
-		voltdm->rmw(vc->common->i2c_cfg_hsen_mask,
+		voltdm->rmw(vc->common->i2c_cfg_clear_mask,
 			    vc->common->i2c_cfg_hsen_mask,
 			    vc->common->i2c_cfg_reg);
 
--- a/arch/arm/mach-omap2/vc.h
+++ b/arch/arm/mach-omap2/vc.h
@@ -34,6 +34,7 @@ struct voltagedomain;
  * @cmd_ret_shift: RET field shift in PRM_VC_CMD_VAL_* register
  * @cmd_off_shift: OFF field shift in PRM_VC_CMD_VAL_* register
  * @i2c_cfg_reg: I2C configuration register offset
+ * @i2c_cfg_clear_mask: high-speed mode bit clear mask in I2C config register
  * @i2c_cfg_hsen_mask: high-speed mode bit field mask in I2C config register
  * @i2c_mcode_mask: MCODE field mask for I2C config register
  *
@@ -52,6 +53,7 @@ struct omap_vc_common {
 	u8 cmd_ret_shift;
 	u8 cmd_off_shift;
 	u8 i2c_cfg_reg;
+	u8 i2c_cfg_clear_mask;
 	u8 i2c_cfg_hsen_mask;
 	u8 i2c_mcode_mask;
 };
--- a/arch/arm/mach-omap2/vc3xxx_data.c
+++ b/arch/arm/mach-omap2/vc3xxx_data.c
@@ -28,6 +28,7 @@
 /*
  * VC data common to 34xx/36xx chips
  * XXX This stuff presumably belongs in the vc3xxx.c or vc.c file.
+ * Note that we must clear SREN to work around erratum 2.11.
  */
 static struct omap_vc_common omap3_vc_common = {
 	.bypass_val_reg	 = OMAP3_PRM_VC_BYPASS_VAL_OFFSET,
@@ -40,6 +41,7 @@ static struct omap_vc_common omap3_vc_common = {
 	.cmd_onlp_shift	 = OMAP3430_VC_CMD_ONLP_SHIFT,
 	.cmd_ret_shift	 = OMAP3430_VC_CMD_RET_SHIFT,
 	.cmd_off_shift	 = OMAP3430_VC_CMD_OFF_SHIFT,
+	.i2c_cfg_clear_mask = OMAP3430_SREN_MASK,
 	.i2c_cfg_hsen_mask = OMAP3430_HSEN_MASK,
 	.i2c_cfg_reg	 = OMAP3_PRM_VC_I2C_CFG_OFFSET,
 	.i2c_mcode_mask	 = OMAP3430_MCODE_MASK,
--- a/arch/arm/mach-omap2/vc44xx_data.c
+++ b/arch/arm/mach-omap2/vc44xx_data.c
@@ -42,6 +42,7 @@ static const struct omap_vc_common omap4_vc_common = {
 	.cmd_ret_shift = OMAP4430_RET_SHIFT,
 	.cmd_off_shift = OMAP4430_OFF_SHIFT,
 	.i2c_cfg_reg = OMAP4_PRM_VC_CFG_I2C_MODE_OFFSET,
+	.i2c_cfg_clear_mask = 0,
 	.i2c_cfg_hsen_mask = OMAP4430_HSMODEEN_MASK,
 	.i2c_mcode_mask	 = OMAP4430_HSMCODE_MASK,
 };