sata_sil24: prevent hba lockup when pass-through ATA commands are used

Fix commands timeout with Sil3124/3132 based HBA when pass-through ATA
commands [where ATA_QCFLAG_RESULT_TF is set] are used while other
commands are active on other devices connected to the same port with a
Port Multiplier.  Due to a hardware bug, these commands must be sent
alone, like ATAPI commands.

Signed-off-by: Gwendal Grignou <gwendal@google.com>
Acked-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 26 insertions, 11 deletions

diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index 96fd5260446d..b4c674d83769 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -832,16 +832,31 @@ static int sil24_qc_defer(struct ata_queued_cmd *qc)
         struct ata_link *link = qc->dev->link;
         struct ata_port *ap = link->ap;
         u8 prot = qc->tf.protocol;
-        int is_atapi = (prot == ATA_PROT_ATAPI ||
-                        prot == ATA_PROT_ATAPI_NODATA ||
-                        prot == ATA_PROT_ATAPI_DMA);
-
-        /* ATAPI commands completing with CHECK_SENSE cause various
-         * weird problems if other commands are active.  PMP DMA CS
-         * errata doesn't cover all and HSM violation occurs even with
-         * only one other device active.  Always run an ATAPI command
-         * by itself.
-         */
+
+        /*
+         * There is a bug in the chip:
+         * Port LRAM Causes the PRB/SGT Data to be Corrupted
+         * If the host issues a read request for LRAM and SActive registers
+         * while active commands are available in the port, PRB/SGT data in
+         * the LRAM can become corrupted. This issue applies only when
+         * reading from, but not writing to, the LRAM.
+         *
+         * Therefore, reading LRAM when there is no particular error [and
+         * other commands may be outstanding] is prohibited.
+         *
+         * To avoid this bug there are two situations where a command must run
+         * exclusive of any other commands on the port:
+         *
+         * - ATAPI commands which check the sense data
+         * - Passthrough ATA commands which always have ATA_QCFLAG_RESULT_TF
+         *   set.
+         *
+         */
+        int is_excl = (prot == ATA_PROT_ATAPI ||
+                       prot == ATA_PROT_ATAPI_NODATA ||
+                       prot == ATA_PROT_ATAPI_DMA ||
+                       (qc->flags & ATA_QCFLAG_RESULT_TF));
+
         if (unlikely(ap->excl_link)) {
                 if (link == ap->excl_link) {
                         if (ap->nr_active_links)
@@ -849,7 +864,7 @@ static int sil24_qc_defer(struct ata_queued_cmd *qc)
                         qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
                 } else
                         return ATA_DEFER_PORT;
-        } else if (unlikely(is_atapi)) {
+        } else if (unlikely(is_excl)) {
                 ap->excl_link = link;
                 if (ap->nr_active_links)
                         return ATA_DEFER_PORT;