tree 187f95b21867318d77b768e1e8be27b0894c239b
parent 792d37af35386466cf5dda51d6b710fa1dd9aad1
author Jian Peng <jipeng2005@gmail.com> 1303541890 -0700
committer Jeff Garzik <jgarzik@pobox.com> 1303659340 -0400

libata: ahci_start_engine compliant to AHCI spec

At the end of section 10.1 of AHCI spec (rev 1.3), it states

Software shall not set PxCMD.ST to 1 until it is determined that
a functoinal device is present on the port as determined by
PxTFD.STS.BSY=0, PxTFD.STS.DRQ=0 and PxSSTS.DET=3h

Even though most AHCI host controller works without this check,
specific controller will fail under this condition.

Signed-off-by: Jian Peng <jipeng2005@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>