[ARM] OMAP3 pwrdm: add hardware save-and-restore (SAR) support

OMAP3430ES2+ introduces a new feature: optional powerdomain context
hardware save-and-restore (SAR).  Currently, this feature only applies
to USBHOST and USBTLL module context when the USBHOST or CORE
powerdomains enter a low-power sleep state[1].  This feature avoids
re-enumeration of USB devices when the powerdomains return from idle,
which is potentially time-consuming.

This patch adds support for enabling and disabling hardware
save-and-restore to the powerdomain code.  Three new functions are
added, pwrdm_enable_hdwr_sar(), pwrdm_disable_hdwr_sar(), and
pwrdm_can_hdwr_sar().  A new struct powerdomain "flags" field is
added, with a PWRDM_HAS_HDWR_SAR flag to indicate powerdomains with
SAR support.

Thanks to Jouni Högander <jouni.hogander@nokia.com> for reviewing an
earlier version of these patches, and Richard Woodruff <r-woodruff2@ti.com>
for clarifying the purpose of these bits.

1.  For the USBHOST controller module, context loss occurs when the
    USBHOST powerdomain enters off-idle.  For USBTLL, context loss
    occurs either if CORE enters off-idle, or if the CORE logic is
    configured to turn off when CORE enters retention-idle (OSWR).
    34xx ES2 TRM 4.8.6.1.1, 4.8.6.1.2

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/arm/plat-omap/include/mach/powerdomain.h b/arch/arm/plat-omap/include/mach/powerdomain.h
index 5fa666fa9be..2806a9c8e4d 100644
--- a/arch/arm/plat-omap/include/mach/powerdomain.h
+++ b/arch/arm/plat-omap/include/mach/powerdomain.h
@@ -38,6 +38,10 @@
 #define PWRSTS_OFF_RET_ON	(PWRSTS_OFF_RET | (1 << PWRDM_POWER_ON))
 
 
+/* Powerdomain flags */
+#define PWRDM_HAS_HDWR_SAR	(1 << 0) /* hardware save-and-restore support */
+
+
 /*
  * Number of memory banks that are power-controllable.	On OMAP3430, the
  * maximum is 4.
@@ -96,6 +100,9 @@ struct powerdomain {
 	/* Possible logic power states when pwrdm in RETENTION */
 	const u8 pwrsts_logic_ret;
 
+	/* Powerdomain flags */
+	const u8 flags;
+
 	/* Number of software-controllable memory banks in this powerdomain */
 	const u8 banks;
 
@@ -150,6 +157,10 @@ int pwrdm_read_prev_logic_pwrst(struct powerdomain *pwrdm);
 int pwrdm_read_mem_pwrst(struct powerdomain *pwrdm, u8 bank);
 int pwrdm_read_prev_mem_pwrst(struct powerdomain *pwrdm, u8 bank);
 
+int pwrdm_enable_hdwr_sar(struct powerdomain *pwrdm);
+int pwrdm_disable_hdwr_sar(struct powerdomain *pwrdm);
+bool pwrdm_has_hdwr_sar(struct powerdomain *pwrdm);
+
 int pwrdm_wait_transition(struct powerdomain *pwrdm);
 
 #endif