From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753569Ab3I0NZ5 (ORCPT ); Fri, 27 Sep 2013 09:25:57 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:33207 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753042Ab3I0NZU (ORCPT ); Fri, 27 Sep 2013 09:25:20 -0400 From: Nishanth Menon To: Liam Girdwood , Mark Brown CC: , Nishanth Menon Subject: [PATCH 2/2] regulator: ti-abb: Fix bias voltage glitch in transition to bypass mode with ldo voltage override Date: Fri, 27 Sep 2013 08:25:14 -0500 Message-ID: <1380288314-24064-3-git-send-email-nm@ti.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1380288314-24064-1-git-send-email-nm@ti.com> References: <1380288314-24064-1-git-send-email-nm@ti.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As documented in Application Note SWPA117 v2.1(NDA), LDO override has a requirement that when switching from Bias active + override active mode(FBB/RBB) to Bypass(nominal) mode, LDO reset must be performed *after* LDO transitions to Bypass(nominal) mode. The same rule in reverse applies when switching from a ABB bypass mode to ABB enabled - LDO override *must* be performed prior to transition to required ABB mode, if we do not do that, the same glitch takes place. Currently while transitioning to ABB bypass, we reset the LDO overide prior to the transition which causes a few milliseconds where ABB LDO voltage could go all the way to 800mV(based on SoC process node), during this period, the delta voltage between VDD rail and VBB rail could cause the system to improperly function. Signed-off-by: Nishanth Menon --- drivers/regulator/ti-abb-regulator.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/regulator/ti-abb-regulator.c b/drivers/regulator/ti-abb-regulator.c index 1e02805..b951a84 100644 --- a/drivers/regulator/ti-abb-regulator.c +++ b/drivers/regulator/ti-abb-regulator.c @@ -279,8 +279,12 @@ static int ti_abb_set_opp(struct regulator_dev *rdev, struct ti_abb *abb, ti_abb_rmw(regs->opp_sel_mask, info->opp_sel, regs->control_reg, abb->base); - /* program LDO VBB vset override if needed */ - if (abb->ldo_base) + /* + * program LDO VBB vset override if needed for !bypass mode + * XXX: Do not switch sequence - for !bypass, LDO override reset *must* + * be performed *before* switch to bias mode else VBB glitches. + */ + if (abb->ldo_base && info->opp_sel != TI_ABB_NOMINAL_OPP) ti_abb_program_ldovbb(dev, abb, info); /* Initiate ABB ldo change */ @@ -295,6 +299,14 @@ static int ti_abb_set_opp(struct regulator_dev *rdev, struct ti_abb *abb, if (ret) goto out; + /* + * Reset LDO VBB vset override bypass mode + * XXX: Do not switch sequence - for bypass, LDO override reset *must* + * be performed *after* switch to bypass else VBB glitches. + */ + if (abb->ldo_base && info->opp_sel == TI_ABB_NOMINAL_OPP) + ti_abb_program_ldovbb(dev, abb, info); + out: return ret; } -- 1.7.9.5