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

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Date:   Mon, 19 Sep 2022 10:46:39 +0100
From:   Eric Curtin <ecurtin@...hat.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        linux-ide@...r.kernel.org
Cc:     Eric Curtin <ecurtin@...hat.com>, linux-kernel@...r.kernel.org,
        Brian Masney <bmasney@...hat.com>, Al Stone <ahs3@...hat.com>,
        Alexander Larsson <alexl@...hat.com>,
        Andrew Halaney <ahalaney@...hat.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Joe Konno <joe.konno@...el.com>
Subject: [PATCH] ata: ahci: Enable/Disable ATA Staggered Spin-up by default

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@...hat.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