Re: [PATCH 7/8] memory: emif: errata i743: Prohibit usage of Power-Down mode
Hi, On Monday 11 March 2013 11:20 AM, Santosh Shilimkar wrote: On Monday 11 March 2013 10:36 AM, Lokesh Vutla wrote: From: Grygorii Strashko grygorii.stras...@ti.com 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 grygorii.stras...@ti.com Signed-off-by: Vitaly Chernooky vitaly.cherno...@ti.com Signed-off-by: Oleksandr Dmytryshyn oleksandr.dmytrys...@ti.com Signed-off-by: Lokesh Vutla lokeshvu...@ti.com --- 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. Yes, it is not applicable for EMIF_4D5 used in OMAP5 ES2.0 Soc's. Ill update this in change log. Thanks Lokesh + 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 santosh.shilim...@ti.com -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH 7/8] memory: emif: errata i743: Prohibit usage of Power-Down mode
From: Grygorii Strashko grygorii.stras...@ti.com 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 grygorii.stras...@ti.com Signed-off-by: Vitaly Chernooky vitaly.cherno...@ti.com Signed-off-by: Oleksandr Dmytryshyn oleksandr.dmytrys...@ti.com Signed-off-by: Lokesh Vutla lokeshvu...@ti.com --- 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-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 7/8] memory: emif: errata i743: Prohibit usage of Power-Down mode
On Monday 11 March 2013 10:36 AM, Lokesh Vutla wrote: From: Grygorii Strashko grygorii.stras...@ti.com 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 grygorii.stras...@ti.com Signed-off-by: Vitaly Chernooky vitaly.cherno...@ti.com Signed-off-by: Oleksandr Dmytryshyn oleksandr.dmytrys...@ti.com Signed-off-by: Lokesh Vutla lokeshvu...@ti.com --- 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 santosh.shilim...@ti.com -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html