[PATCH] ata: ahci: Enable/Disable ATA Staggered Spin-up by default

[Eric Curtin <ecurtin@redhat.com>]

On some kernels tuned for performance, you want to always favour
spin-up time versus power draw. This adds the ability to always favour
spin-up time by default (disabling Staggered Spin-up favours
performance, rather than power draw).

Regardless of whether this is enabled or disabled the
libahci.ignore_sss option will override any kernel config.

Signed-off-by: Eric Curtin <ecurtin@redhat.com>
---
 drivers/ata/Kconfig   | 15 +++++++++++++++
 drivers/ata/libahci.c |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/Kconfig b/drivers/ata/Kconfig
index 1c9f4fb2595d..36b11fbcf644 100644
--- a/drivers/ata/Kconfig
+++ b/drivers/ata/Kconfig
@@ -67,6 +67,21 @@ config ATA_FORCE
 
 	  If unsure, say Y.
 
+config ATA_SSS
+        bool "Enable ATA Staggered Spin-up by default"
+        default y
+        help
+          This option denotes whether Staggered Spin-up capability on
+          storage controllers is used. Staggered Spin-up reduces
+          peak power draw, but decreases performance. If this config is
+          set to N, Staggered Spin-up capability will be ignored by
+          default.
+
+          This can be overridden by using the kernel argument
+          libahci.ignore_sss.
+
+          If unsure, say Y.
+
 config ATA_ACPI
 	bool "ATA ACPI Support"
 	depends on ACPI
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index cf8c7fd59ada..b7b573d47fda 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -33,7 +33,7 @@
 #include "libata.h"
 
 static int ahci_skip_host_reset;
-int ahci_ignore_sss;
+int ahci_ignore_sss = !IS_ENABLED(CONFIG_ATA_SSS);
 EXPORT_SYMBOL_GPL(ahci_ignore_sss);
 
 module_param_named(skip_host_reset, ahci_skip_host_reset, int, 0444);
-- 
2.37.3