[PATCH v6 07/10] drivers/char: add RX support to the XHCI driver

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Add another work ring buffer for received data, and point IN TRB at it.
Ensure there is always at least one pending IN TRB, so the controller
has a way to send incoming data to the driver.
Note that both "success" and "short packet" completion codes are okay -
in fact it will be "short packet" most of the time, as the TRB length is
about maximum size, not required size.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Changes in v4:
- adjust return types
- add some const
New patch in v3
---
 docs/misc/xen-command-line.pandoc |   6 +-
 xen/drivers/char/xhci-dbc.c       | 129 +++++++++++++++++++++++++++++++-
 2 files changed, 132 insertions(+), 3 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc 
b/docs/misc/xen-command-line.pandoc
index f6bdae9ca5f4..fb4d80c590f3 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -731,9 +731,9 @@ Available alternatives, with their meaning, are:
 Specify the USB controller to use, either by instance number (when going
 over the PCI busses sequentially) or by PCI device (must be on segment 0).
 
-Use `ehci` for EHCI debug port, use `xhci` for XHCI debug capability (output
-only). XHCI driver will wait indefinitely for the debug host to connect - make
-sure the cable is connected.
+Use `ehci` for EHCI debug port, use `xhci` for XHCI debug capability.
+XHCI driver will wait indefinitely for the debug host to connect - make sure
+the cable is connected.
 
 ### debug_stack_lines
 > `= <integer>`
diff --git a/xen/drivers/char/xhci-dbc.c b/xen/drivers/char/xhci-dbc.c
index fc9745f7c2ac..557c5fc785ce 100644
--- a/xen/drivers/char/xhci-dbc.c
+++ b/xen/drivers/char/xhci-dbc.c
@@ -111,6 +111,7 @@ enum {
 enum {
     XHCI_TRB_CC_SUCCESS = 1,
     XHCI_TRB_CC_TRB_ERR = 5,
+    XHCI_TRB_CC_SHORT_PACKET = 13,
 };
 
 /* DbC endpoint types */
@@ -239,6 +240,7 @@ struct dbc {
     struct xhci_trb_ring dbc_oring;
     struct xhci_trb_ring dbc_iring;
     struct dbc_work_ring dbc_owork;
+    struct dbc_work_ring dbc_iwork;
     struct xhci_string_descriptor *dbc_str;
 
     pci_sbdf_t sbdf;
@@ -444,6 +446,16 @@ static void xhci_trb_norm_set_ioc(struct xhci_trb *trb)
     trb->ctrl |= 0x20;
 }
 
+static uint64_t xhci_trb_norm_buf(const struct xhci_trb *trb)
+{
+    return trb->params;
+}
+
+static uint32_t xhci_trb_norm_len(const struct xhci_trb *trb)
+{
+    return trb->status & 0x1FFFF;
+}
+
 /**
  * Fields for Transfer Event TRBs (see section 6.4.2.1). Note that event
  * TRBs are read-only from software
@@ -453,6 +465,17 @@ static uint64_t xhci_trb_tfre_ptr(const struct xhci_trb 
*trb)
     return trb->params;
 }
 
+static uint32_t xhci_trb_tfre_cc(const struct xhci_trb *trb)
+{
+    return trb->status >> 24;
+}
+
+/* Amount of data _not_ transferred */
+static uint32_t xhci_trb_tfre_len(const struct xhci_trb *trb)
+{
+    return trb->status & 0x1FFFF;
+}
+
 /* Fields for link TRBs (section 6.4.4.1) */
 static void xhci_trb_link_set_rsp(struct xhci_trb *trb, uint64_t rsp)
 {
@@ -494,6 +517,14 @@ static bool xhci_trb_ring_full(const struct xhci_trb_ring 
*ring)
     return ((ring->enq + 1) & (DBC_TRB_RING_CAP - 1)) == ring->deq;
 }
 
+static unsigned int xhci_trb_ring_size(const struct xhci_trb_ring *ring)
+{
+    if ( ring->enq >= ring->deq )
+        return ring->enq - ring->deq;
+
+    return DBC_TRB_RING_CAP - ring->deq + ring->enq;
+}
+
 static bool dbc_work_ring_full(const struct dbc_work_ring *ring)
 {
     return ((ring->enq + 1) & (DBC_WORK_RING_CAP - 1)) == ring->deq;
@@ -507,6 +538,14 @@ static unsigned int dbc_work_ring_size(const struct 
dbc_work_ring *ring)
     return DBC_WORK_RING_CAP - ring->deq + ring->enq;
 }
 
+static unsigned int dbc_work_ring_space_to_end(const struct dbc_work_ring 
*ring)
+{
+    if ( ring->enq >= ring->deq )
+        return DBC_WORK_RING_CAP - ring->enq;
+
+    return ring->deq - ring->enq;
+}
+
 static void dbc_push_trb(struct dbc *dbc, struct xhci_trb_ring *ring,
                          uint64_t dma, uint64_t len)
 {
@@ -567,6 +606,31 @@ static unsigned int dbc_push_work(struct dbc *dbc, struct 
dbc_work_ring *ring,
     return i;
 }
 
+static void dbc_rx_trb(struct dbc *dbc, struct xhci_trb *trb,
+                       uint64_t not_transferred)
+{
+    struct dbc_work_ring *ring = &dbc->dbc_iwork;
+    unsigned int rx_len;
+    unsigned int end, start = ring->enq;
+
+    if ( xhci_trb_type(trb) != XHCI_TRB_NORM )
+        /* Can be Link TRB for example. */
+        return;
+
+    ASSERT(xhci_trb_norm_buf(trb) == ring->dma + ring->enq);
+    ASSERT(xhci_trb_norm_len(trb) >= not_transferred);
+    rx_len = xhci_trb_norm_len(trb) - not_transferred;
+
+    /* It can hit the ring end, but should not wrap around. */
+    ASSERT(ring->enq + rx_len <= DBC_WORK_RING_CAP);
+    ring->enq = (ring->enq + rx_len) & (DBC_WORK_RING_CAP - 1);
+
+    end = ring->enq;
+
+    if ( end > start )
+        cache_flush(&ring->buf[start], end - start);
+}
+
 /*
  * Note that if IN transfer support is added, then this
  * will need to be changed; it assumes an OUT transfer ring only
@@ -576,6 +640,7 @@ static void dbc_pop_events(struct dbc *dbc)
     struct dbc_reg *reg = dbc->dbc_reg;
     struct xhci_trb_ring *er = &dbc->dbc_ering;
     struct xhci_trb_ring *tr = &dbc->dbc_oring;
+    struct xhci_trb_ring *ir = &dbc->dbc_iring;
     struct xhci_trb *event = &er->trb[er->deq];
     uint64_t erdp = readq(&reg->erdp);
     uint32_t portsc;
@@ -601,6 +666,14 @@ static void dbc_pop_events(struct dbc *dbc)
                 trb_idx = (event_ptr - tr->dma) >> XHCI_TRB_SHIFT;
                 tr->deq = (trb_idx + 1) & (DBC_TRB_RING_CAP - 1);
             }
+            else if ( event_ptr - ir->dma < DBC_TRB_RING_BYTES )
+            {
+                trb_idx = (event_ptr - ir->dma) >> XHCI_TRB_SHIFT;
+                if ( xhci_trb_tfre_cc(event) == XHCI_TRB_CC_SUCCESS ||
+                     xhci_trb_tfre_cc(event) == XHCI_TRB_CC_SHORT_PACKET )
+                    dbc_rx_trb(dbc, &ir->trb[trb_idx], 
xhci_trb_tfre_len(event));
+                ir->deq = (trb_idx + 1) & (DBC_TRB_RING_CAP - 1);
+            }
             else
                 dbc_alert("event: TRB 0x%lx not found in any ring\n",
                           event_ptr);
@@ -871,6 +944,7 @@ static bool __init dbc_open(struct dbc *dbc)
         return false;
 
     dbc_init_work_ring(dbc, &dbc->dbc_owork);
+    dbc_init_work_ring(dbc, &dbc->dbc_iwork);
     dbc_enable_dbc(dbc);
     dbc->open = true;
 
@@ -947,6 +1021,33 @@ static void dbc_flush(struct dbc *dbc, struct 
xhci_trb_ring *trb,
 }
 
 /**
+ * Ensure DbC has a pending transfer TRB to receive data into.
+ *
+ * @param dbc the dbc to flush
+ * @param trb the ring for the TRBs to transfer
+ * @param wrk the work ring to receive data into
+ */
+static void dbc_enqueue_in(struct dbc *dbc, struct xhci_trb_ring *trb,
+                           struct dbc_work_ring *wrk)
+{
+    struct dbc_reg *reg = dbc->dbc_reg;
+    uint32_t db = (readl(&reg->db) & 0xFFFF00FF) | (trb->db << 8);
+
+    /* Check if there is already queued TRB */
+    if ( xhci_trb_ring_size(trb) >= 1 )
+        return;
+
+    if ( dbc_work_ring_full(wrk) )
+        return;
+
+    dbc_push_trb(dbc, trb, wrk->dma + wrk->enq,
+                 dbc_work_ring_space_to_end(wrk));
+
+    wmb();
+    writel(db, &reg->db);
+}
+
+/**
  * Queue a single character to the DbC. A transfer TRB will be created
  * if the character is a newline and the DbC will be notified that data is
  * available for writing to the debug host.
@@ -969,6 +1070,19 @@ static int64_t dbc_putc(struct dbc *dbc, char c)
     return 1;
 }
 
+static int dbc_getc(struct dbc *dbc, char *c)
+{
+    struct dbc_work_ring *wrk = &dbc->dbc_iwork;
+
+    if ( dbc_work_ring_size(wrk) == 0 )
+        return 0;
+
+    *c = wrk->buf[wrk->deq];
+    wrk->deq = (wrk->deq + 1) & (DBC_WORK_RING_CAP - 1);
+
+    return 1;
+}
+
 struct dbc_uart {
     struct dbc dbc;
     struct timer timer;
@@ -987,10 +1101,16 @@ static void cf_check dbc_uart_poll(void *data)
     if ( spin_trylock_irqsave(&port->tx_lock, flags) )
     {
         if ( dbc_ensure_running(dbc) )
+        {
             dbc_flush(dbc, &dbc->dbc_oring, &dbc->dbc_owork);
+            dbc_enqueue_in(dbc, &dbc->dbc_iring, &dbc->dbc_iwork);
+        }
         spin_unlock_irqrestore(&port->tx_lock, flags);
     }
 
+    while ( dbc_work_ring_size(&dbc->dbc_iwork) )
+        serial_rx_interrupt(port, guest_cpu_user_regs());
+
     serial_tx_interrupt(port, guest_cpu_user_regs());
     set_timer(&uart->timer, NOW() + MICROSECS(DBC_POLL_INTERVAL));
 }
@@ -1029,6 +1149,12 @@ static void cf_check dbc_uart_putc(struct serial_port 
*port, char c)
     dbc_putc(&uart->dbc, c);
 }
 
+static int cf_check dbc_uart_getc(struct serial_port *port, char *c)
+{
+    struct dbc_uart *uart = port->uart;
+    return dbc_getc(&uart->dbc, c);
+}
+
 static void cf_check dbc_uart_flush(struct serial_port *port)
 {
     s_time_t goal;
@@ -1048,6 +1174,7 @@ static struct uart_driver dbc_uart_driver = {
     .init_postirq = dbc_uart_init_postirq,
     .tx_ready = dbc_uart_tx_ready,
     .putc = dbc_uart_putc,
+    .getc = dbc_uart_getc,
     .flush = dbc_uart_flush,
 };
 
@@ -1057,6 +1184,7 @@ struct dbc_dma_bufs {
     struct xhci_trb out_trb[DBC_TRB_RING_CAP];
     struct xhci_trb in_trb[DBC_TRB_RING_CAP];
     uint8_t out_wrk_buf[DBC_WORK_RING_CAP];
+    uint8_t in_wrk_buf[DBC_WORK_RING_CAP];
     struct xhci_erst_segment erst __aligned(16);
     struct xhci_dbc_ctx ctx __aligned(16);
     struct xhci_string_descriptor str_buf[DBC_STRINGS_COUNT];
@@ -1118,6 +1246,7 @@ void __init xhci_dbc_uart_init(void)
     dbc->dbc_oring.trb = dbc_dma_bufs.out_trb;
     dbc->dbc_iring.trb = dbc_dma_bufs.in_trb;
     dbc->dbc_owork.buf = dbc_dma_bufs.out_wrk_buf;
+    dbc->dbc_iwork.buf = dbc_dma_bufs.in_wrk_buf;
     dbc->dbc_str = dbc_dma_bufs.str_buf;
 
     if ( dbc_open(dbc) )
-- 
git-series 0.9.1