[PATCH 1/3][SRU][OEM-B] SAUCE: ata: libahci: Correct setting of DEVSLP register

AceLan Kao acelan.kao at canonical.com
Fri Jul 13 06:31:04 UTC 2018


From: Srinivas Pandruvada <srinivas.pandruvada at linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/1781533

We have seen that on some platforms, SATA device never show any DEVSLP
residency. This prevent power gating of SATA IP, which prevent system
to transition to low power mode in systems with SLP_S0 aka modern
standby systems. The PHY logic is off only in DEVSLP not in slumber.
Reference:
https://www.intel.com/content/dam/www/public/us/en/documents/datasheets
/332995-skylake-i-o-platform-datasheet-volume-1.pdf
Section 28.7.6.1

Here driver is trying to do read-modify-write the devslp register. But
not resetting the bits for which this driver will modify values (DITO,
MDAT and DETO). So simply reset those bits before updating to new values.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada at linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
---
 drivers/ata/libahci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index a0de7a38430c..40d8dcd175e3 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -2145,6 +2145,8 @@ static void ahci_set_aggressive_devslp(struct ata_port *ap, bool sleep)
 		deto = 20;
 	}
 
+	/* Make dito, mdat, deto bits to 0s */
+	devslp &= ~GENMASK_ULL(24, 2);
 	devslp |= ((dito << PORT_DEVSLP_DITO_OFFSET) |
 		   (mdat << PORT_DEVSLP_MDAT_OFFSET) |
 		   (deto << PORT_DEVSLP_DETO_OFFSET) |
-- 
2.17.1





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