ARM: OMAP2+: Fix omap 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 i531 "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@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
Cc: stable@vger.kernel.org # v3.16+
sys_clkreq and sys_off_mode")
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/arch/arm/mach-omap2/vc.c b/arch/arm/mach-omap2/vc.c
index be9ef834fa81..076fd20d7e5a 100644
--- 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 i531.
 	 */
 	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 i531 "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 extra 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);