On Tue, Oct 18, 2022 at 02:24:00PM +0100, John Garry wrote: > Hi guys, > > In the hisi_sas driver there are times in which we need to issue an ATA > software reset. For this we use hisi_sas_softreset_ata_disk() -> > sas_execute_ata_cmd() -> sas_execute_tmf(), which uses libsas "slow task" > mechanism to issue the command. > > I would like if libata provided such a function to issue a software reset, > such that we can send the command as an ATA queued command. > > The problem is that often when we would want to issue this software reset > the associated ata port is frozen, like in ATA EH, and so we cannot issue > ATA queued commands - internal or normal - at that time. > > Is there any way to solve this? Or I am just misunderstanding how and when > ATA queued commands can and should be used? > Hello John, See the kdoc above __ata_port_freeze(): "This function is called when HSM violation or some other condition disrupts normal operation of the port. Frozen port is not allowed to perform any operation until the port is thawed, which usually follows a successful reset. ap->ops->freeze() callback can be used for freezing the port hardware-wise (e.g. mask interrupt and stop DMA engine). If a port cannot be frozen hardware-wise, the interrupt handler must ack and clear interrupts unconditionally while the port is frozen." ata_port_operations.qc_issue() is obviously an operation on the port, so it makes sense that it is not allowed. Interrupts are also usually masked or disabled at this time, so we won't get an IRQ with the completion. Perhaps one could argue that there could be an API to execute a polled command. But if the port is in a bad state, e.g. a HSM error (RDY bit is not set), issuing a command would likely fail anyway, regardless if using polling or IRQs. > I assume that ata_port_operations.softreset callback requires a method to be > able to issue the softreset directly from the driver, like ahci_softreset() > -> ahci_do_softreset() -> ahci_exec_polled_cmd(). Yes, looking .softreset in a few ata drivers, they all seem issue the softreset directly from the driver. (e.g. ahci_do_softreset() calls ahci_exec_polled_cmd() which just always uses bit 0 in PORT_CMD_ISSUE, so it ignores hw_tag.) But I don't think that I fully understand your problem. hisi_sas_softreset_ata_disk() -> sas_execute_ata_cmd() -> sas_execute_tmf() calls lldd_execute_task() (hisi_sas_queue_command()) and then calls waits for completion. How is this different from e.g. the libahci case? Doesn't this end up being the same as resetting the port directly from the driver? (if we ignore all the callbacks) Or do you actually get stuck on a ata_port_is_frozen() check somewhere? Kind regards, Niklas
