When cable is unplugged, dbc_ensure_running() correctly detects this
situation (DBC_CTRL_DCR flag is clear), and prevent sending data
immediately to the device. It gets only queued in work ring buffers.
When cable is plugged in again, subsequent dbc_flush() will send the
buffered data.
But there is a corner case, where no subsequent data was buffered in the
work buffer, but a TRB was still pending. Ring the doorbell to let the
controller re-send them. For console output it is rare corner case (TRB
is pending for a very short time), but for console input it is very
normal case (there is always one pending TRB for input).
Extract doorbell ringing into separate function to avoid duplication.
Signed-off-by: Marek Marczykowski-Górecki
---
Changes in v6:
- keep barriers consistent
---
xen/drivers/char/xhci-dbc.c | 17 -
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/xen/drivers/char/xhci-dbc.c b/xen/drivers/char/xhci-dbc.c
index 9f7e1dd60a78..829f1d1d910f 100644
--- a/xen/drivers/char/xhci-dbc.c
+++ b/xen/drivers/char/xhci-dbc.c
@@ -554,6 +554,15 @@ static unsigned int dbc_work_ring_space_to_end(const
struct dbc_work_ring *ring)
return ring->deq - ring->enq;
}
+static void dbc_ring_doorbell(struct dbc *dbc, int doorbell)
+{
+uint32_t __iomem *db_reg = >dbc_reg->db;
+uint32_t db = (readl(db_reg) & ~DBC_DOORBELL_TARGET_MASK) |
+ (doorbell << DBC_DOORBELL_TARGET_SHIFT);
+
+writel(db, db_reg);
+}
+
static void dbc_push_trb(struct dbc *dbc, struct xhci_trb_ring *ring,
uint64_t dma, uint64_t len)
{
@@ -1024,6 +1033,8 @@ static bool dbc_ensure_running(struct dbc *dbc)
writel(ctrl | (1U << DBC_CTRL_DRC), >ctrl);
writel(readl(>portsc) | (1U << DBC_PSC_PED), >portsc);
wmb();
+dbc_ring_doorbell(dbc, dbc->dbc_iring.db);
+dbc_ring_doorbell(dbc, dbc->dbc_oring.db);
}
return true;
@@ -1041,10 +1052,6 @@ static bool dbc_ensure_running(struct dbc *dbc)
static void dbc_flush(struct dbc *dbc, struct xhci_trb_ring *trb,
struct dbc_work_ring *wrk)
{
-struct dbc_reg *reg = dbc->dbc_reg;
-uint32_t db = (readl(>db) & ~DBC_DOORBELL_TARGET_MASK) |
- (trb->db << DBC_DOORBELL_TARGET_SHIFT);
-
if ( xhci_trb_ring_full(trb) )
return;
@@ -1068,7 +1075,7 @@ static void dbc_flush(struct dbc *dbc, struct
xhci_trb_ring *trb,
}
wmb();
-writel(db, >db);
+dbc_ring_doorbell(dbc, trb->db);
}
/**
--
git-series 0.9.1
