libahci: Allow drivers to override start_engine

Allwinner A10 and A20 ARM SoCs have an AHCI sata controller which needs a
special register to be poked before starting the DMA engine.

This register gets reset on an ahci_stop_engine call, so there is no other
place then ahci_start_engine where this poking can be done.

This commit allows drivers to override ahci_start_engine behavior for use by
the Allwinner AHCI driver (and potentially other drivers in the future).

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 2289efdf8203..64d1a99de5e4 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -323,6 +323,12 @@ struct ahci_host_priv {
         u32                     em_msg_type;    /* EM message type */
         struct clk              *clk;           /* Only for platforms supporting clk */
         void                    *plat_data;     /* Other platform data */
+        /*
+         * Optional ahci_start_engine override, if not set this gets set to the
+         * default ahci_start_engine during ahci_save_initial_config, this can
+         * be overridden anytime before the host is activated.
+         */
+        void                    (*start_engine)(struct ata_port *ap);
 };
 
 extern int ahci_ignore_sss;