Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752176Ab3CKFsZ (ORCPT ); Mon, 11 Mar 2013 01:48:25 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:49948 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751130Ab3CKFsX (ORCPT ); Mon, 11 Mar 2013 01:48:23 -0400 Message-ID: <513D708D.1000501@ti.com> Date: Mon, 11 Mar 2013 11:20:05 +0530 From: Santosh Shilimkar User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Lokesh Vutla CC: , , , , Grygorii Strashko , Vitaly Chernooky , Oleksandr Dmytryshyn Subject: Re: [PATCH 7/8] memory: emif: errata i743: Prohibit usage of Power-Down mode References: <1362978365-5593-1-git-send-email-lokeshvutla@ti.com> <1362978365-5593-8-git-send-email-lokeshvutla@ti.com> In-Reply-To: <1362978365-5593-8-git-send-email-lokeshvutla@ti.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4100 Lines: 89 On Monday 11 March 2013 10:36 AM, Lokesh Vutla wrote: > From: Grygorii Strashko > > ERRATA DESCRIPTION : > The EMIF supports power-down state for low power. The EMIF > automatically puts the SDRAM into power-down after the memory is > not accessed for a defined number of cycles and the > EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field is set to 0x4. > As the EMIF supports automatic output impedance calibration, a ZQ > calibration long command is issued every time it exits active > power-down and precharge power-down modes. The EMIF waits and > blocks any other command during this calibration. > The EMIF does not allow selective disabling of ZQ calibration upon > exit of power-down mode. Due to very short periods of power-down > cycles, ZQ calibration overhead creates bandwidth issues and > increases overall system power consumption. On the other hand, > issuing ZQ calibration long commands when exiting self-refresh is > still required. > > WORKAROUND : > Because there is no power consumption benefit of the power-down due > to the calibration and there is a performance risk, the guideline > is to not allow power-down state and, therefore, to not have set > the EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field to 0x4. > > Signed-off-by: Grygorii Strashko > Signed-off-by: Vitaly Chernooky > Signed-off-by: Oleksandr Dmytryshyn > Signed-off-by: Lokesh Vutla > --- Nice changelog. > drivers/memory/emif.c | 35 +++++++++++++++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/drivers/memory/emif.c b/drivers/memory/emif.c > index f75806a..119503a 100644 > --- a/drivers/memory/emif.c > +++ b/drivers/memory/emif.c > @@ -257,6 +257,41 @@ static void set_lpmode(struct emif_data *emif, u8 lpmode) > u32 temp; > void __iomem *base = emif->base; > > + /* > + * Workaround for errata i743 - LPDDR2 Power-Down State is Not > + * Efficient > + * > + * i743 DESCRIPTION: > + * The EMIF supports power-down state for low power. The EMIF > + * automatically puts the SDRAM into power-down after the memory is > + * not accessed for a defined number of cycles and the > + * EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field is set to 0x4. > + * As the EMIF supports automatic output impedance calibration, a ZQ > + * calibration long command is issued every time it exits active > + * power-down and precharge power-down modes. The EMIF waits and > + * blocks any other command during this calibration. > + * The EMIF does not allow selective disabling of ZQ calibration upon > + * exit of power-down mode. Due to very short periods of power-down > + * cycles, ZQ calibration overhead creates bandwidth issues and > + * increases overall system power consumption. On the other hand, > + * issuing ZQ calibration long commands when exiting self-refresh is > + * still required. > + * > + * WORKAROUND > + * Because there is no power consumption benefit of the power-down due > + * to the calibration and there is a performance risk, the guideline > + * is to not allow power-down state and, therefore, to not have set > + * the EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field to 0x4. > + */ > + if ((emif->plat_data->ip_rev == EMIF_4D) && > + (EMIF_LP_MODE_PWR_DN == lpmode)) { Ok. So the errata is limited to only 'EMIF_4D' version and not applicable for next EMIF version used in OMAP5 devices, right ? If yes, would be good to just mention that in already good changelog. > + WARN_ONCE(1, > + "REG_LP_MODE = LP_MODE_PWR_DN(4) is prohibited by" > + "erratum i743 switch to LP_MODE_SELF_REFRESH(2)\n"); > + /* rallback LP_MODE to Self-refresh mode */ s/rallback/rollback ? With above updates, Acked-by: Santosh Shilimkar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/