Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751927Ab3CKFGZ (ORCPT ); Mon, 11 Mar 2013 01:06:25 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:45344 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751295Ab3CKFGW (ORCPT ); Mon, 11 Mar 2013 01:06:22 -0400 From: Lokesh Vutla To: , , CC: , , Grygorii Strashko , Vitaly Chernooky , Oleksandr Dmytryshyn , Lokesh Vutla Subject: [PATCH 7/8] memory: emif: errata i743: Prohibit usage of Power-Down mode Date: Mon, 11 Mar 2013 10:36:04 +0530 Message-ID: <1362978365-5593-8-git-send-email-lokeshvutla@ti.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1362978365-5593-1-git-send-email-lokeshvutla@ti.com> References: <1362978365-5593-1-git-send-email-lokeshvutla@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 Content-Length: 3762 Lines: 86 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 --- 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)) { + 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 */ + lpmode = EMIF_LP_MODE_SELF_REFRESH; + } + temp = readl(base + EMIF_POWER_MANAGEMENT_CONTROL); temp &= ~LP_MODE_MASK; temp |= (lpmode << LP_MODE_SHIFT); -- 1.7.9.5 -- 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/