[SeaBIOS] [PATCH] ahci: set transfer mode according to the capabilities of connected drive

[Kevin O'Connor]

On Sat, Feb 20, 2016 at 03:20:15PM +0100, Gerd Hoffmann wrote:
> Use case: cf cards behind sata-ide bridge, which might not support
> the default transfer mode.
> 
> Based on a patch by Werner Zeh <werner.zeh at siemens.com>,
> with some minor tweaks applied.
> 
> Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
> ---
>  src/hw/ahci.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  src/hw/ata.h  |  5 +++++
>  2 files changed, 63 insertions(+)
> 
> diff --git a/src/hw/ahci.c b/src/hw/ahci.c
> index 9310850..ea862f2 100644
> --- a/src/hw/ahci.c
> +++ b/src/hw/ahci.c
> @@ -515,6 +515,64 @@ static int ahci_port_setup(struct ahci_port_s *port)
>                                , ata_extract_version(buffer)
>                                , (u32)adjsize, adjprefix);
>          port->prio = bootprio_find_ata_device(ctrl->pci_tmp, pnr, 0);
> +
> +        s8 multi_dma = -1;
> +        s8 pio_mode = -1;
> +        s8 udma_mode = -1;
> +        // If bit 2 in word 53 is set, udma information is valid in word 88.
> +        if (buffer[53] & 0x04) {
> +                udma_mode = 6;
> +                while ((udma_mode >= 0) &&
> +                        !((buffer[88] & 0x7f) & ( 1 << udma_mode ))) {
> +                        udma_mode--;
> +                }
> +        }
> +        // If bit 1 in word 53 is set, multiword-dma and advanced pio modes
> +        // are available in words 63 and 64.
> +        if (buffer[53] & 0x02) {
> +                pio_mode = 4;
> +                multi_dma = 3;
> +                while ((multi_dma >= 0) &&
> +                       !((buffer[63] & 0x7) & ( 1 << multi_dma ))) {
> +                        multi_dma--;
> +                }

This indentation should be fixed.

Otherwise, looks good to me.
-Kevin