[PATCH v2 4/7] ata: libata: respect successfully completed commands during errors

Niklas Cassel
2022-12-29T17:00:34Z

In AHCI specification 1.3.1:
"5.5.3 Processing Completed Commands"

"For each port that has an interrupt pending:

1. Software determines the cause of the interrupt by reading the PxIS
register. It is possible for multiple bits to be set.
2. Software clears appropriate bits in the PxIS register corresponding
to the cause of the interrupt.
3. Software clears the interrupt bit in IS.IPS corresponding to the port.
4. If executing non-queued commands, software reads the PxCI register,
and compares the current value to the list of commands previously
issued by software that are still outstanding. If executing native
queued commands, software reads the PxSACT register and compares the
current value to the list of commands previously issued by software.
Software completes with success any outstanding command whose
corresponding bit has been cleared in the respective register. PxCI
and PxSACT are volatile registers; software should only use their
values to determine commands that have completed, not to determine
which commands have previously been issued.
5. If there were errors, noted in the PxIS register, software performs
error recovery actions (see section 6.2.2)."

The documentation for the PxSACT shadow register in AHCI:
"The device clears bits in this field by sending a Set Device Bits FIS
to the host. The HBA clears bits in this field that are set to ‘1’ in
the SActive field of the Set Device Bits FIS. The HBA only clears bits
that correspond to native queued commands that have completed
successfully."

Additionally, in SATA specification 3.5a:
"11.15 FPDMA QUEUED command protocol"

"DFPDMAQ11: ERROR
Halt command processing and transmit Set Device Bits FIS to host
with the ERR bit in Status field set to one, Interrupt bit set to one,
ATA error code set to one in the ERROR field, bits in ACT field cleared
to zero for any outstanding queued commands, and bits set to one
for any successfully completed queued commands that completion
notification not yet delivered."

I.e. even when the HBA triggers an error interrupt, the HBA will still
clear successfully completed commands in PxSACT. Commands that did not
complete successfully will still have its bit set in PxSACT.
(Which means the command that caused the NCQ error and queued commands
that had not yet finished at the time when the NCQ error occurred.)

Additionally, for a HBA that does not have the libata flag
AHCI_HFLAG_MULTI_MSI set, all ap->locks will point to host->lock, which
means that IRQs will be disabled for one port while another port's IRQ
handler is running. The HBA will still receive FISes from the device,
even if IRQs on the HBA itself are disabled. What can thus e.g. receive
a FIS that completes several commands successfully, followed by a FIS
that does (or does not) complete additional commands with the error bit
set, to indicate that at least one command was aborted.

Therefore, modify ahci_handle_port_interrupt() using the new helper
ahci_qc_complete() to complete the commands that have already been
signaled as successfully through a regular completion SDB FIS, as not
doing so would simply cause successfully completed commands to be
retried for no good reason.

Co-developed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
---
drivers/ata/libahci.c | 73 +++++++++++++++++++++++++------------------
1 file changed, 42 insertions(+), 31 deletions(-)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index e5d67eb46f3c..8f216de76648 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1849,18 +1849,47 @@ static void ahci_error_intr(struct ata_port *ap, u32 irq_stat)
ata_port_abort(ap);
}

-static void ahci_handle_port_interrupt(struct ata_port *ap,
- void __iomem *port_mmio, u32 status)
+static void ahci_qc_complete(struct ata_port *ap, void __iomem *port_mmio)
{
struct ata_eh_info *ehi = &ap->link.eh_info;
struct ahci_port_priv *pp = ap->private_data;
- struct ahci_host_priv *hpriv = ap->host->private_data;
- int resetting = !!(ap->pflags & ATA_PFLAG_RESETTING);
u32 qc_active = 0;
int rc;

+ /*
+ * pp->active_link is not reliable once FBS is enabled, both
+ * PORT_SCR_ACT and PORT_CMD_ISSUE should be checked because
+ * NCQ and non-NCQ commands may be in flight at the same time.
+ */
+ if (pp->fbs_enabled) {
+ if (ap->qc_active) {
+ qc_active = readl(port_mmio + PORT_SCR_ACT);
+ qc_active |= readl(port_mmio + PORT_CMD_ISSUE);
+ }
+ } else {
+ /* pp->active_link is valid iff any command is in flight */
+ if (ap->qc_active && pp->active_link->sactive)
+ qc_active = readl(port_mmio + PORT_SCR_ACT);
+ else
+ qc_active = readl(port_mmio + PORT_CMD_ISSUE);
+ }
+
+ rc = ata_qc_complete_multiple(ap, qc_active);
+ if (unlikely(rc < 0 && !(ap->pflags & ATA_PFLAG_RESETTING))) {
+ ehi->err_mask |= AC_ERR_HSM;
+ ehi->action |= ATA_EH_RESET;
+ ata_port_freeze(ap);
+ }
+}
+
+static void ahci_handle_port_interrupt(struct ata_port *ap,
+ void __iomem *port_mmio, u32 status)
+{
+ struct ahci_port_priv *pp = ap->private_data;
+ struct ahci_host_priv *hpriv = ap->host->private_data;
+
/* ignore BAD_PMP while resetting */
- if (unlikely(resetting))
+ if (unlikely(ap->pflags & ATA_PFLAG_RESETTING))
status &= ~PORT_IRQ_BAD_PMP;

if (sata_lpm_ignore_phy_events(&ap->link)) {
@@ -1869,6 +1898,12 @@ static void ahci_handle_port_interrupt(struct ata_port *ap,
}

if (unlikely(status & PORT_IRQ_ERROR)) {
+ /*
+ * Before getting the error notification, we may have
+ * received SDB FISes notifying successful completions.
+ * Handle these first and then handle the error.
+ */
+ ahci_qc_complete(ap, port_mmio);
ahci_error_intr(ap, status);
return;
}
@@ -1905,32 +1940,8 @@ static void ahci_handle_port_interrupt(struct ata_port *ap,
}
}

- /* pp->active_link is not reliable once FBS is enabled, both
- * PORT_SCR_ACT and PORT_CMD_ISSUE should be checked because
- * NCQ and non-NCQ commands may be in flight at the same time.
- */
- if (pp->fbs_enabled) {
- if (ap->qc_active) {
- qc_active = readl(port_mmio + PORT_SCR_ACT);
- qc_active |= readl(port_mmio + PORT_CMD_ISSUE);
- }
- } else {
- /* pp->active_link is valid iff any command is in flight */
- if (ap->qc_active && pp->active_link->sactive)
- qc_active = readl(port_mmio + PORT_SCR_ACT);
- else
- qc_active = readl(port_mmio + PORT_CMD_ISSUE);
- }
-
-
- rc = ata_qc_complete_multiple(ap, qc_active);
-
- /* while resetting, invalid completions are expected */
- if (unlikely(rc < 0 && !resetting)) {
- ehi->err_mask |= AC_ERR_HSM;
- ehi->action |= ATA_EH_RESET;
- ata_port_freeze(ap);
- }
+ /* Handle completed commands */
+ ahci_qc_complete(ap, port_mmio);
}

static void ahci_port_intr(struct ata_port *ap)
--
2.38.1