* disk/ata.c (grub_ata_wait_status): Replace by ...
(grub_ata_wait_not_busy): ... this function. Checks only BSY bit,
other status bits may be invalid while BSY is asserted.
(grub_ata_check_ready): New function.
(grub_ata_cmd): Removed.
(grub_ata_wait_drq): New function.
(grub_ata_strncpy): Remove inline.
(grub_ata_pio_read): Reduce to actual block transfer. BSY wait
and error check now done by grub_ata_wait_drq ().
(grub_ata_pio_write): Likewise.
(grub_atapi_identify): Set DEV before check for !BSY. Use
grub_ata_wait_drq () to wait for data.
(grub_ata_device_initialize): Add status register check to
detect missing SATA slave devices. Add debug messages.
(grub_atapi_wait_drq): Use grub_ata_wait_not_busy ().
(grub_atapi_packet): Set DEV before check for !BSY. Replace
transfer loop by grub_ata_pio_write ().
(grub_ata_identify): Set DEV before check for !BSY. Use
grub_ata_wait_drq () to wait for data.
(grub_ata_setaddress): Set DEV before check for !BSY.
(grub_ata_readwrite): Remove duplicate code, handle batch/rest and
read/write in one loop. Fix invalid command on write. Fix incomplete
command on (size % batch) == 0. Add missing error check after write of
last block. Add debug messages.
(grub_atapi_read): Replace transfer loop by grub_ata_pio_read ().