[PATCH] libata: implement presence detection via polling IDENTIFY
On some controllers (ICHs in piix mode), there is *NO* reliable way to
determine device presence other than issuing IDENTIFY and see how the
transaction proceeds by watching the TF status register.
libata acted this way before irq-pio and phantom devices caused very
little problem but now that IDENTIFY is performed using IRQ drive PIO,
such phantom devices now result in multiple 30sec timeouts during
boot.
This patch implements ATA_FLAG_DETECT_POLLING. If a LLD sets this
flag, libata core issues the initial IDENTIFY in polling mode and if
the initial data transfer fails w/ HSM violation, the port is
considered to be empty thus replicating the old libata and IDE
behavior.
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 090abe4..21f8d61 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1272,9 +1272,20 @@
tf.protocol = ATA_PROT_PIO;
+ /* presence detection using polling IDENTIFY? */
+ if (flags & ATA_READID_DETECT)
+ tf.flags |= ATA_TFLAG_POLLING;
+
err_mask = ata_exec_internal(dev, &tf, NULL, DMA_FROM_DEVICE,
id, sizeof(id[0]) * ATA_ID_WORDS);
if (err_mask) {
+ if ((flags & ATA_READID_DETECT) &&
+ (err_mask & AC_ERR_NODEV_HINT)) {
+ DPRINTK("ata%u.%d: NODEV after polling detection\n",
+ ap->id, dev->devno);
+ return -ENOENT;
+ }
+
rc = -EIO;
reason = "I/O error";
goto err_out;
@@ -4285,8 +4296,12 @@
/* device stops HSM for abort/error */
qc->err_mask |= AC_ERR_DEV;
else
- /* HSM violation. Let EH handle this */
- qc->err_mask |= AC_ERR_HSM;
+ /* HSM violation. Let EH handle this.
+ * Phantom devices also trigger this
+ * condition. Mark hint.
+ */
+ qc->err_mask |= AC_ERR_HSM |
+ AC_ERR_NODEV_HINT;
ap->hsm_task_state = HSM_ST_ERR;
goto fsm_start;