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[v2,1/2] UBUNTU: SAUCE: ata: libahci: Correct setting of DEVSLP register

Message ID 20180718012632.11232-2-acelan.kao@canonical.com
State New
Headers show
Series [v2,1/2] UBUNTU: SAUCE: ata: libahci: Correct setting of DEVSLP register | expand

Commit Message

AceLan Kao July 18, 2018, 1:26 a.m. UTC 
From: Srinivas Pandruvada <srinivas.pandruvada@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.

Link: https://patchwork.kernel.org/patch/10502285/

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

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) |