From: Grygorii Strashko Date: Sat, 16 Mar 2013 06:16:47 +0000 (+0530) Subject: memory: emif: errata i743: Prohibit usage of Power-Down mode X-Git-Tag: omap-for-v3.10/dt-fixes-for-merge-window~139^2~69 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f02503b2ff73d3b09ca27335304611a206d2b54a;p=pandora-kernel.git memory: emif: errata i743: Prohibit usage of Power-Down mode 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. This is applicable only for EMIF4D IP used in OMAP4 Soc's. Signed-off-by: Grygorii Strashko Signed-off-by: Vitaly Chernooky Signed-off-by: Oleksandr Dmytryshyn Signed-off-by: Lokesh Vutla Acked-by: Santosh Shilimkar Signed-off-by: Greg Kroah-Hartman --- Reading git-diff-tree failed