On 04/12/2013 01:34 PM, Marc C wrote:
Hello Jeff,
I'm working with a proprietary but AHCI-compatible SATA controller that uses
the libata driver. Early versions of this controller have issues with processing
non-data ATAPI commands. A workaround was identified which requires some
register pokes in the command completion path of the driver. I don't expect to
push this patch upstream (yet). However, I would like to get some feedback
regarding the workaround, and check if the placement of the code is "acceptable"
or if there would be a better place to put it.
The workaround itself is rather simple: toggle the START bit immediately after a
non-data ATAPI command completes. The ST bit toggle would be performed within
atomic context in the AHCI port interrupt ISR.
Signed-off-by: Marc C <marc.ceeeee@xxxxxxxxx>
This should likely be triggered off a host flag like some of the ones
already in the driver so it can be done just for the affected
controllers, not unconditionally.
---
linux/drivers/ata/libahci.c | 26 ++++++++++++++++++++++++++
linux/drivers/ata/libata-core.c | 6 ++++++
2 files changed, 32 insertions(+)
diff --git a/linux/drivers/ata/libahci.c b/linux/drivers/ata/libahci.c
index f9eaa82..20b3a9a 100644
--- a/linux/drivers/ata/libahci.c
+++ b/linux/drivers/ata/libahci.c
@@ -2215,6 +2215,32 @@ void ahci_set_em_messages(struct ahci_host_priv *hpriv,
}
EXPORT_SYMBOL_GPL(ahci_set_em_messages);
+void ahci_apply_atapi_workaround(struct ata_queued_cmd *qc)
+{
+ if (!(qc->flags & ATA_QCFLAG_DMAMAP)) {
+ /*
+ * Non-data ATAPI commands need to kick the DMA engine
+ */
+ struct ata_port *ap = qc->ap;
+ void __iomem *port_mmio = ahci_port_base(ap);
+ u32 tmp = readl(port_mmio + PORT_CMD);
+
+ /* check if the HBA is idle */
+ if ((tmp & (PORT_CMD_START | PORT_CMD_LIST_ON)) != 0) {
+ /* setting HBA to idle */
+ tmp &= ~PORT_CMD_START;
+ writel(tmp, port_mmio + PORT_CMD);
+
+ /* wait for engine to stop */
+ do {
+ tmp = readl(port_mmio + PORT_CMD);
+ } while (tmp & PORT_CMD_LIST_ON);
+ }
+ ahci_start_engine(ap);
+ }
+}
+EXPORT_SYMBOL_GPL(ahci_apply_atapi_workaround);
+
MODULE_AUTHOR("Jeff Garzik");
MODULE_DESCRIPTION("Common AHCI SATA low-level routines");
MODULE_LICENSE("GPL");
diff --git a/linux/drivers/ata/libata-core.c b/linux/drivers/ata/libata-core.c
index 4e73e1b..383de21 100644
--- a/linux/drivers/ata/libata-core.c
+++ b/linux/drivers/ata/libata-core.c
@@ -4827,6 +4827,12 @@ void ata_qc_complete(struct ata_queued_cmd *qc)
{
struct ata_port *ap = qc->ap;
+ if (ata_is_atapi(qc->tf.protocol)) {
+ void ahci_apply_atapi_workaround(struct ata_queued_cmd *qc);
+ ahci_apply_atapi_workaround(qc);
+ }
+
/* XXX: New EH and old EH use different mechanisms to
* synchronize EH with regular execution path.
*
--
1.7.9.5
--
Regards,
Marc
marc.ceeeee@xxxxxxxxx
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