ata: libata-eh: Fix link state check for IDE/PATA ports

Commit 4371fe1 ("ata: libata-eh: Avoid unnecessary resets when
revalidating devices") replaced the call to ata_phys_link_offline() in
ata_eh_revalidate_and_attach() with the new function
ata_eh_link_established() which relaxes the checks on a device link
state to account for low power mode transitions. However, this change
assumed that the device port has a valid scr_read method to obtain the
SStatus register for the port. This is not always the case, especially
with older IDE/PATA adapters (e.g. PATA/IDE devices emulated with QEMU).
For such adapter, ata_eh_link_established() will always return false,
causing ata_eh_revalidate_and_attach() to go into its error path and
ultimately to the device being disabled.

Avoid this by restoring the previous behavior, which is to assume that
the link is online if reading the port SStatus register fails.

While at it, also fix the spelling of SStatus in the comment describing
the function ata_eh_link_established().

Reported-by: Shin'ichiro Kawasaki <[email protected]>
Fixes: 4371fe1 ("ata: libata-eh: Avoid unnecessary resets when revalidating devices")
Signed-off-by: Damien Le Moal <[email protected]>
Tested-by: Shin'ichiro Kawasaki <[email protected]>
Reviewed-by: Niklas Cassel <[email protected]>

Author: damien-lemoal

drivers/ata/libata-eh.c

@@ -2075,7 +2075,7 @@ static void ata_eh_get_success_sense(struct ata_link *link)
  * Check if a link is established. This is a relaxed version of
  * ata_phys_link_online() which accounts for the fact that this is potentially
  * called after changing the link power management policy, which may not be
- * reflected immediately in the SSTAUS register (e.g., we may still be seeing
+ * reflected immediately in the SStatus register (e.g., we may still be seeing
  * the PHY in partial, slumber or devsleep Partial power management state.
  * So check that:
  * - A device is still present, that is, DET is 1h (Device presence detected
@@ -2089,8 +2089,13 @@ static bool ata_eh_link_established(struct ata_link *link)
 	u32 sstatus;
 	u8 det, ipm;
 
+	/*
+	 * For old IDE/PATA adapters that do not have a valid scr_read method,
+	 * or if reading the SStatus register fails, assume that the device is
+	 * present. Device probe will determine if that is really the case.
+	 */
 	if (sata_scr_read(link, SCR_STATUS, &sstatus))
-		return false;
+		return true;
 
 	det = sstatus & 0x0f;
 	ipm = (sstatus >> 8) & 0x0f;