Hi,
During the review of the ATA/8 Serial Transport material in the February T13 Summit a few items were given to me as the liaison into the SATA-IO to research the meaning or intent. Below are the questions and responses I've recorded in finding the details.
1. What was the original intent of listing 'Freeze' as a valid category for error responses? (see sections 10.1 & 10.5.2 of d1697r0a-ATA8-ST, where Freeze has been removed)
<Original reference in sections 11.1 (pg 273) and 11.5.2 (pg 279) of Serial ATA 1.0a.>
Freeze is the condition the drive enters where a host action like a reset is required to recover the drive. Whether you admit it or not, it is not unusual for drives to enter this state. Serial ATA might have been the first to explicitly call this behavior out, although it is not an unusual occurrence. In hopelessly messed up situations, it is probably safer for a drive to halt and await the host cleaning up with a reset than it might be for the drive to proceed and potentially exacerbate the situation.
2. Why isn't BIST Activate included in the list of frame types that can be retransmitted? (see section 10.4.3.2 of d1697r0a-ATA8-ST)
<Original reference in section 11.4.2.2 (page 278) of Serial ATA 1.0a.>
BIST is not a function performed during the normal course of operation for a disk drive. Since it’s an engineering lab-bench function to be used in controlled conditions by knowledgeable experts, it does not have the kinds of automatic recovery that normal user functions might have. In some lab settings, it could even be detrimental for auto-recovery operations to be performed by the interface, since some lab functions are for the purpose of examining such behaviors. If the BIST Activate function fails in a lab setting, the engineer is presumably sufficiently capable to know what is happening and attempt the operation over again.
With the understanding of the above explanations, I believe that 'Freeze' should be re-inserted back into the ATA/8 material and that BIST Activate should still not exist in the list referred to by question #2. This would require three total edits, although minor, into the next revision of the document.
Regards,
Brian
