[Qemu-devel] [PATCH v5 03/15] ssi: Implemented CS behaviour

[Peter A. G. Crosthwaite]

Added default CS behaviour for SSI slaves. SSI devices can set a property
to enable CS behaviour which will create a GPIO on the device which is the
CS. Tristating of the bus on SSI transfers is implemented.

Signed-off-by: Peter A. G. Crosthwaite <address@hidden>
---
 hw/ssd0323.c |    6 ++++++
 hw/ssi-sd.c  |    6 ++++++
 hw/ssi.c     |   39 ++++++++++++++++++++++++++++++++++++++-
 hw/ssi.h     |   27 +++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 1 deletions(-)

diff --git a/hw/ssd0323.c b/hw/ssd0323.c
index b0b2e94..db16d20 100644
--- a/hw/ssd0323.c
+++ b/hw/ssd0323.c
@@ -277,6 +277,7 @@ static void ssd0323_cd(void *opaque, int n, int level)
 
 static void ssd0323_save(QEMUFile *f, void *opaque)
 {
+    SSISlave *ss = SSI_SLAVE(opaque);
     ssd0323_state *s = (ssd0323_state *)opaque;
     int i;
 
@@ -294,10 +295,13 @@ static void ssd0323_save(QEMUFile *f, void *opaque)
     qemu_put_be32(f, s->remap);
     qemu_put_be32(f, s->mode);
     qemu_put_buffer(f, s->framebuffer, sizeof(s->framebuffer));
+
+    qemu_put_be32(f, ss->cs ? 1 : 0);
 }
 
 static int ssd0323_load(QEMUFile *f, void *opaque, int version_id)
 {
+    SSISlave *ss = SSI_SLAVE(opaque);
     ssd0323_state *s = (ssd0323_state *)opaque;
     int i;
 
@@ -319,6 +323,8 @@ static int ssd0323_load(QEMUFile *f, void *opaque, int 
version_id)
     s->mode = qemu_get_be32(f);
     qemu_get_buffer(f, s->framebuffer, sizeof(s->framebuffer));
 
+    ss->cs = !!qemu_get_be32(f);
+
     return 0;
 }
 
diff --git a/hw/ssi-sd.c b/hw/ssi-sd.c
index b519bdb..6fd9ab9 100644
--- a/hw/ssi-sd.c
+++ b/hw/ssi-sd.c
@@ -197,6 +197,7 @@ static uint32_t ssi_sd_transfer(SSISlave *dev, uint32_t val)
 
 static void ssi_sd_save(QEMUFile *f, void *opaque)
 {
+    SSISlave *ss = SSI_SLAVE(opaque);
     ssi_sd_state *s = (ssi_sd_state *)opaque;
     int i;
 
@@ -209,10 +210,13 @@ static void ssi_sd_save(QEMUFile *f, void *opaque)
     qemu_put_be32(f, s->arglen);
     qemu_put_be32(f, s->response_pos);
     qemu_put_be32(f, s->stopping);
+
+    qemu_put_be32(f, ss->cs ? 1 : 0);
 }
 
 static int ssi_sd_load(QEMUFile *f, void *opaque, int version_id)
 {
+    SSISlave *ss = SSI_SLAVE(opaque);
     ssi_sd_state *s = (ssi_sd_state *)opaque;
     int i;
 
@@ -229,6 +233,8 @@ static int ssi_sd_load(QEMUFile *f, void *opaque, int 
version_id)
     s->response_pos = qemu_get_be32(f);
     s->stopping = qemu_get_be32(f);
 
+    ss->cs = !!qemu_get_be32(f);
+
     return 0;
 }
 
diff --git a/hw/ssi.c b/hw/ssi.c
index 2db88fc..2e4f2fe 100644
--- a/hw/ssi.c
+++ b/hw/ssi.c
@@ -27,19 +27,55 @@ static const TypeInfo ssi_bus_info = {
     .instance_size = sizeof(SSIBus),
 };
 
+static void ssi_cs_default(void *opaque, int n, int level)
+{
+    SSISlave *s = SSI_SLAVE(opaque);
+    bool cs = !!level;
+    assert(n == 0);
+    if (s->cs != cs) {
+        SSISlaveClass *ssc = SSI_SLAVE_GET_CLASS(s);
+        if (ssc->set_cs) {
+            ssc->set_cs(s, cs);
+        }
+    }
+    s->cs = cs;
+}
+
+static uint32_t ssi_transfer_raw_default(SSISlave *dev, uint32_t val)
+{
+    SSISlaveClass *ssc = SSI_SLAVE_GET_CLASS(dev);
+
+    if ((dev->cs && ssc->cs_polarity == SSI_CS_HIGH) ||
+            (!dev->cs && ssc->cs_polarity == SSI_CS_LOW) ||
+            ssc->cs_polarity == SSI_CS_NONE) {
+        return ssc->transfer(dev, val);
+    }
+    return 0;
+}
+
 static int ssi_slave_init(DeviceState *dev)
 {
     SSISlave *s = SSI_SLAVE(dev);
     SSISlaveClass *ssc = SSI_SLAVE_GET_CLASS(s);
 
+    if (ssc->transfer_raw == ssi_transfer_raw_default &&
+            ssc->cs_polarity != SSI_CS_NONE) {
+        qdev_init_gpio_in(&s->qdev, ssi_cs_default, 1);
+    }
+
     return ssc->init(s);
 }
 
 static void ssi_slave_class_init(ObjectClass *klass, void *data)
 {
+    SSISlaveClass *ssc = SSI_SLAVE_CLASS(klass);
     DeviceClass *dc = DEVICE_CLASS(klass);
+
     dc->init = ssi_slave_init;
     dc->bus_type = TYPE_SSI_BUS;
+    if (!ssc->transfer_raw) {
+        ssc->transfer_raw = ssi_transfer_raw_default;
+    }
 }
 
 static TypeInfo ssi_slave_info = {
@@ -74,7 +110,7 @@ uint32_t ssi_transfer(SSIBus *bus, uint32_t val)
     QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
         SSISlave *slave = SSI_SLAVE(kid->child);
         ssc = SSI_SLAVE_GET_CLASS(slave);
-        r |= ssc->transfer(slave, val);
+        r |= ssc->transfer_raw(slave, val);
     }
 
     return r;
@@ -86,6 +122,7 @@ const VMStateDescription vmstate_ssi_slave = {
     .minimum_version_id = 1,
     .minimum_version_id_old = 1,
     .fields      = (VMStateField[]) {
+        VMSTATE_BOOL(cs, SSISlave),
         VMSTATE_END_OF_LIST()
     }
 };
diff --git a/hw/ssi.h b/hw/ssi.h
index 975f9fb..5b69a3b 100644
--- a/hw/ssi.h
+++ b/hw/ssi.h
@@ -23,16 +23,43 @@ typedef struct SSISlave SSISlave;
 #define SSI_SLAVE_GET_CLASS(obj) \
      OBJECT_GET_CLASS(SSISlaveClass, (obj), TYPE_SSI_SLAVE)
 
+typedef enum {
+    SSI_CS_NONE = 0,
+    SSI_CS_LOW,
+    SSI_CS_HIGH,
+} SSICSMode;
+
 /* Slave devices.  */
 typedef struct SSISlaveClass {
     DeviceClass parent_class;
 
     int (*init)(SSISlave *dev);
+
+    /* if you have standard or no CS behaviour, just override transfer.
+     * This is called when the device cs is active (true by default).
+     */
     uint32_t (*transfer)(SSISlave *dev, uint32_t val);
+    /* called when the CS line changes. Optional, devices only need to 
implement
+     * this if they have side effects assoicated with the cs line (beyond
+     * tristating the txrx lines).
+     */
+    int (*set_cs)(SSISlave *dev, bool select);
+    /* define whether or not CS exists and is active low/high */
+    SSICSMode cs_polarity;
+
+    /* if you have non-standard CS behvaiour override this to take control
+     * of the CS behvaiour at the device level. transfer, set_cs, and
+     * cs_polarity are unused if this is overwritten. Transfer_raw, will
+     * always be called for the device for every txrx access the to parent bus
+     */
+    uint32_t (*transfer_raw)(SSISlave *dev, uint32_t val);
 } SSISlaveClass;
 
 struct SSISlave {
     DeviceState qdev;
+
+    /* Chip select state */
+    bool cs;
 };
 
 #define SSI_SLAVE_FROM_QDEV(dev) DO_UPCAST(SSISlave, qdev, dev)
-- 
1.7.0.4