diff options
author | Grygorii Strashko <grygorii.strashko@ti.com> | 2013-03-16 02:16:47 -0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-03-25 16:18:13 -0400 |
commit | f02503b2ff73d3b09ca27335304611a206d2b54a (patch) | |
tree | b378994b306e55cc2fd2fab20449637e5e1250f9 /drivers/memory | |
parent | 36caf3e525b24556f649aecd097cad73bde6f035 (diff) |
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 <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>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/memory')
-rw-r--r-- | drivers/memory/emif.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/drivers/memory/emif.c b/drivers/memory/emif.c index 9335339ebfdf..bd223c7c3e72 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) | |||
257 | u32 temp; | 257 | u32 temp; |
258 | void __iomem *base = emif->base; | 258 | void __iomem *base = emif->base; |
259 | 259 | ||
260 | /* | ||
261 | * Workaround for errata i743 - LPDDR2 Power-Down State is Not | ||
262 | * Efficient | ||
263 | * | ||
264 | * i743 DESCRIPTION: | ||
265 | * The EMIF supports power-down state for low power. The EMIF | ||
266 | * automatically puts the SDRAM into power-down after the memory is | ||
267 | * not accessed for a defined number of cycles and the | ||
268 | * EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field is set to 0x4. | ||
269 | * As the EMIF supports automatic output impedance calibration, a ZQ | ||
270 | * calibration long command is issued every time it exits active | ||
271 | * power-down and precharge power-down modes. The EMIF waits and | ||
272 | * blocks any other command during this calibration. | ||
273 | * The EMIF does not allow selective disabling of ZQ calibration upon | ||
274 | * exit of power-down mode. Due to very short periods of power-down | ||
275 | * cycles, ZQ calibration overhead creates bandwidth issues and | ||
276 | * increases overall system power consumption. On the other hand, | ||
277 | * issuing ZQ calibration long commands when exiting self-refresh is | ||
278 | * still required. | ||
279 | * | ||
280 | * WORKAROUND | ||
281 | * Because there is no power consumption benefit of the power-down due | ||
282 | * to the calibration and there is a performance risk, the guideline | ||
283 | * is to not allow power-down state and, therefore, to not have set | ||
284 | * the EMIF_PWR_MGMT_CTRL[10:8] REG_LP_MODE bit field to 0x4. | ||
285 | */ | ||
286 | if ((emif->plat_data->ip_rev == EMIF_4D) && | ||
287 | (EMIF_LP_MODE_PWR_DN == lpmode)) { | ||
288 | WARN_ONCE(1, | ||
289 | "REG_LP_MODE = LP_MODE_PWR_DN(4) is prohibited by" | ||
290 | "erratum i743 switch to LP_MODE_SELF_REFRESH(2)\n"); | ||
291 | /* rollback LP_MODE to Self-refresh mode */ | ||
292 | lpmode = EMIF_LP_MODE_SELF_REFRESH; | ||
293 | } | ||
294 | |||
260 | temp = readl(base + EMIF_POWER_MANAGEMENT_CONTROL); | 295 | temp = readl(base + EMIF_POWER_MANAGEMENT_CONTROL); |
261 | temp &= ~LP_MODE_MASK; | 296 | temp &= ~LP_MODE_MASK; |
262 | temp |= (lpmode << LP_MODE_SHIFT); | 297 | temp |= (lpmode << LP_MODE_SHIFT); |