| Message ID | 1362978365-5593-8-git-send-email-lokeshvutla@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Monday 11 March 2013 10:36 AM, Lokesh Vutla wrote: > From: Grygorii Strashko <grygorii.strashko@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.strashko@ti.com> > Signed-off-by: Vitaly Chernooky <vitaly.chernooky@ti.com> > Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> > Signed-off-by: Lokesh Vutla <lokeshvutla@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.shilimkar@ti.com> -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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.strashko@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.strashko@ti.com> >> Signed-off-by: Vitaly Chernooky <vitaly.chernooky@ti.com> >> Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@ti.com> >> Signed-off-by: Lokesh Vutla <lokeshvutla@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.shilimkar@ti.com> > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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);