From: Oliver Schinagl <oli...@schinagl.nl>

Allwinner A10 and A20 ARM SoCs have an AHCI sata controller which need 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 adds a pre ahci_start_engine hook for use by the Allwinner AHCI
driver (and potentially other drivers in the future).

Signed-off-by: Hans de Goede <hdego...@redhat.com>
---
 drivers/ata/ahci.h    | 2 ++
 drivers/ata/libahci.c | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 2289efd..1bba479 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -323,6 +323,8 @@ 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 pre ahci_start_engine hook */
+       void                    (*pre_start_engine)(struct ata_port *ap);
 };
 
 extern int ahci_ignore_sss;
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index c482f8c..780e9df 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -568,8 +568,12 @@ static int ahci_scr_write(struct ata_link *link, unsigned 
int sc_reg, u32 val)
 void ahci_start_engine(struct ata_port *ap)
 {
        void __iomem *port_mmio = ahci_port_base(ap);
+       struct ahci_host_priv *hpriv = ap->host->private_data;
        u32 tmp;
 
+       if (hpriv->pre_start_engine)
+               hpriv->pre_start_engine(ap);
+
        /* start DMA */
        tmp = readl(port_mmio + PORT_CMD);
        tmp |= PORT_CMD_START;
-- 
1.8.4.2

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