[Qemu-devel] [PATCH v3 14/16] register: Add GPIO API

[Alistair Francis]

From: Peter Crosthwaite <address@hidden>

Add GPIO functionality to the register API. This allows association
and automatic connection of GPIOs to bits in registers. GPIO inputs
will attach to handlers that automatically set read-only bits in
registers. GPIO outputs will be updated to reflect their field value
when their respective registers are written (or reset). Supports
active low GPIOs.

This is particularly effective for implementing system level
controllers, where heterogenous collections of control signals are
placed is a SoC specific peripheral then propagated all over the
system.

Signed-off-by: Peter Crosthwaite <address@hidden>
[ EI Changes:
  * register: Add a polarity field to GPIO connections
              Makes it possible to directly connect active low signals
              to generic interrupt pins.
]
Signed-off-by: Edgar E. Iglesias <address@hidden>
Signed-off-by: Alistair Francis <address@hidden>
---

 hw/core/register.c    | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/register.h | 26 ++++++++++++++
 2 files changed, 120 insertions(+)

diff --git a/hw/core/register.c b/hw/core/register.c
index 4d7dd95..f461cd7 100644
--- a/hw/core/register.c
+++ b/hw/core/register.c
@@ -138,6 +138,8 @@ void register_write(RegisterInfo *reg, uint64_t val, 
uint64_t we)
 
 register_write_fast:
     register_write_val(reg, new_val);
+    register_refresh_gpios(reg, old_val);
+
     if (ac->post_write) {
         ac->post_write(reg, new_val);
     }
@@ -180,18 +182,85 @@ uint64_t register_read(RegisterInfo *reg)
 void register_reset(RegisterInfo *reg)
 {
     assert(reg);
+    uint64_t old_val;
 
     if (!reg->data || !reg->access) {
         return;
     }
 
+    old_val = register_read_val(reg);
+
     register_write_val(reg, reg->access->reset);
+    register_refresh_gpios(reg, old_val);
+}
+
+void register_refresh_gpios(RegisterInfo *reg, uint64_t old_value)
+{
+    const RegisterAccessInfo *ac;
+    const RegisterGPIOMapping *gpio;
+
+    ac = reg->access;
+    for (gpio = ac->gpios; gpio && gpio->name; gpio++) {
+        int i;
+
+        if (gpio->input) {
+            continue;
+        }
+
+        for (i = 0; i < gpio->num; ++i) {
+            uint64_t gpio_value, gpio_value_old;
+
+            qemu_irq gpo = qdev_get_gpio_out_named(DEVICE(reg), gpio->name, i);
+            gpio_value_old = extract64(old_value,
+                                       gpio->bit_pos + i * gpio->width,
+                                       gpio->width) ^ gpio->polarity;
+            gpio_value = extract64(register_read_val(reg),
+                                   gpio->bit_pos + i * gpio->width,
+                                   gpio->width) ^ gpio->polarity;
+            if (!(gpio_value_old ^ gpio_value)) {
+                continue;
+            }
+            if (reg->debug && gpo) {
+                qemu_log("refreshing gpio out %s to %" PRIx64 "\n",
+                         gpio->name, gpio_value);
+            }
+            qemu_set_irq(gpo, gpio_value);
+        }
+    }
+}
+
+typedef struct DeviceNamedGPIOHandlerOpaque {
+    DeviceState *dev;
+    const char *name;
+} DeviceNamedGPIOHandlerOpaque;
+
+static void register_gpio_handler(void *opaque, int n, int level)
+{
+    DeviceNamedGPIOHandlerOpaque *gho = opaque;
+    RegisterInfo *reg = REGISTER(gho->dev);
+
+    const RegisterAccessInfo *ac;
+    const RegisterGPIOMapping *gpio;
+
+    ac = reg->access;
+    for (gpio = ac->gpios; gpio && gpio->name; gpio++) {
+        if (gpio->input && !strcmp(gho->name, gpio->name)) {
+            register_write_val(reg, deposit64(register_read_val(reg),
+                                              gpio->bit_pos + n * gpio->width,
+                                              gpio->width,
+                                              level ^ gpio->polarity));
+            return;
+        }
+    }
+
+    abort();
 }
 
 void register_init(RegisterInfo *reg)
 {
     assert(reg);
     const RegisterAccessInfo *ac;
+    const RegisterGPIOMapping *gpio;
 
     if (!reg->data || !reg->access) {
         return;
@@ -200,6 +269,30 @@ void register_init(RegisterInfo *reg)
     object_initialize((void *)reg, sizeof(*reg), TYPE_REGISTER);
 
     ac = reg->access;
+    for (gpio = ac->gpios; gpio && gpio->name; gpio++) {
+        if (!gpio->num) {
+            ((RegisterGPIOMapping *)gpio)->num = 1;
+        }
+        if (!gpio->width) {
+            ((RegisterGPIOMapping *)gpio)->width = 1;
+        }
+        if (gpio->input) {
+            DeviceNamedGPIOHandlerOpaque gho = {
+                .name = gpio->name,
+                .dev = DEVICE(reg),
+            };
+            qemu_irq irq;
+
+            qdev_init_gpio_in_named(DEVICE(reg), register_gpio_handler,
+                                    gpio->name, gpio->num);
+            irq = qdev_get_gpio_in_named(DEVICE(reg), gpio->name, gpio->num);
+            qemu_irq_set_opaque(irq, g_memdup(&gho, sizeof(gho)));
+        } else {
+            qemu_irq *gpos = g_new0(qemu_irq, gpio->num);
+
+            qdev_init_gpio_out_named(DEVICE(reg), gpos, gpio->name, gpio->num);
+        }
+    }
 
     /* if there are no debug msgs and no RMW requirement, mark for fast write 
*/
     reg->write_lite = reg->debug || ac->ro || ac->w1c || ac->pre_write ||
@@ -279,6 +372,7 @@ void register_init_block32(DeviceState *owner, const 
RegisterAccessInfo *rae,
             .opaque = owner,
         };
         register_init(r);
+        qdev_pass_all_gpios(DEVICE(r), owner);
 
         memory_region_init_io(&r->mem, OBJECT(owner), ops, r, r->access->name,
                               sizeof(uint32_t));
diff --git a/include/hw/register.h b/include/hw/register.h
index 30dedbf..9a8a94b 100644
--- a/include/hw/register.h
+++ b/include/hw/register.h
@@ -13,6 +13,7 @@
 
 #include "hw/qdev-core.h"
 #include "exec/memory.h"
+#include "hw/irq.h"
 
 typedef struct RegisterInfo RegisterInfo;
 typedef struct RegisterAccessInfo RegisterAccessInfo;
@@ -28,6 +29,18 @@ typedef struct RegisterAccessError {
     const char *reason;
 } RegisterAccessError;
 
+#define REG_GPIO_POL_HIGH 0
+#define REG_GPIO_POL_LOW  1
+
+typedef struct RegisterGPIOMapping {
+    const char *name;
+    uint8_t bit_pos;
+    bool input;
+    bool polarity;
+    uint8_t num;
+    uint8_t width;
+} RegisterGPIOMapping;
+
 /**
  * Access description for a register that is part of guest accessible device
  * state.
@@ -78,6 +91,8 @@ struct RegisterAccessInfo {
 
     uint64_t (*post_read)(RegisterInfo *reg, uint64_t val);
 
+    const RegisterGPIOMapping *gpios;
+
     struct {
         hwaddr addr;
     } decode;
@@ -157,6 +172,17 @@ void register_reset(RegisterInfo *reg);
 void register_init(RegisterInfo *reg);
 
 /**
+ * Refresh GPIO outputs based on diff between old value register current value.
+ * GPIOs are refreshed for fields where the old value differs to the current
+ * value.
+ *
+ * @reg: Register to refresh GPIO outs
+ * @old_value: previous value of register
+ */
+
+void register_refresh_gpios(RegisterInfo *reg, uint64_t old_value);
+
+/**
  * Memory API MMIO write handler that will write to a Register API register.
  *  _be for big endian variant and _le for little endian.
  * @opaque: RegisterInfo to write to
-- 
2.5.0