static int ahci_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val);
static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val);
static int ahci_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val);
static int ahci_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val);