versatilepb: Implement SYS_CLCD mux control register bits

On the Versatile PB, PL110 graphics adaptor only natively supports
5551 pixel format; an external mux swaps bits around to allow
RGB565 and BGR565, under the control of bits [1:0] in the SYS_CLCD
system register.

Implement these SYS_CLCD register bits, and use a gpio line to
feed them out of the system register model, across the versatilepb
board and into the pl110 so we can select the right format.

This is necessary as recent Linux versatile kernels default to
programming the CLCD and mux for 16 bit BGR rather than 16 bit RGB.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 46 insertions, 3 deletions

diff --git a/hw/arm_sysctl.c b/hw/arm_sysctl.c
index fd0c8bc3d..22c62dfeb 100644
--- a/hw/arm_sysctl.c
+++ b/hw/arm_sysctl.c
@@ -17,6 +17,8 @@
 
 typedef struct {
     SysBusDevice busdev;
+    qemu_irq pl110_mux_ctrl;
+
     uint32_t sys_id;
     uint32_t leds;
     uint16_t lockval;
@@ -30,11 +32,12 @@ typedef struct {
     uint32_t sys_cfgdata;
     uint32_t sys_cfgctrl;
     uint32_t sys_cfgstat;
+    uint32_t sys_clcd;
 } arm_sysctl_state;
 
 static const VMStateDescription vmstate_arm_sysctl = {
     .name = "realview_sysctl",
-    .version_id = 2,
+    .version_id = 3,
     .minimum_version_id = 1,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(leds, arm_sysctl_state),
@@ -48,6 +51,7 @@ static const VMStateDescription vmstate_arm_sysctl = {
         VMSTATE_UINT32_V(sys_cfgdata, arm_sysctl_state, 2),
         VMSTATE_UINT32_V(sys_cfgctrl, arm_sysctl_state, 2),
         VMSTATE_UINT32_V(sys_cfgstat, arm_sysctl_state, 2),
+        VMSTATE_UINT32_V(sys_clcd, arm_sysctl_state, 3),
         VMSTATE_END_OF_LIST()
     }
 };
@@ -78,6 +82,13 @@ static void arm_sysctl_reset(DeviceState *d)
     s->cfgdata2 = 0;
     s->flags = 0;
     s->resetlevel = 0;
+    if (board_id(s) == BOARD_ID_VEXPRESS) {
+        /* On VExpress this register will RAZ/WI */
+        s->sys_clcd = 0;
+    } else {
+        /* All others: CLCDID 0x1f, indicating VGA */
+        s->sys_clcd = 0x1f00;
+    }
 }
 
 static uint32_t arm_sysctl_read(void *opaque, target_phys_addr_t offset)
@@ -124,7 +135,7 @@ static uint32_t arm_sysctl_read(void *opaque, target_phys_addr_t offset)
     case 0x4c: /* FLASH */
         return 0;
     case 0x50: /* CLCD */
-        return 0x1000;
+        return s->sys_clcd;
     case 0x54: /* CLCDSER */
         return 0;
     case 0x58: /* BOOTCS */
@@ -232,7 +243,39 @@ static void arm_sysctl_write(void *opaque, target_phys_addr_t offset,
         /* nothing to do.  */
         break;
     case 0x4c: /* FLASH */
+        break;
     case 0x50: /* CLCD */
+        switch (board_id(s)) {
+        case BOARD_ID_PB926:
+            /* On 926 bits 13:8 are R/O, bits 1:0 control
+             * the mux that defines how to interpret the PL110
+             * graphics format, and other bits are r/w but we
+             * don't implement them to do anything.
+             */
+            s->sys_clcd &= 0x3f00;
+            s->sys_clcd |= val & ~0x3f00;
+            qemu_set_irq(s->pl110_mux_ctrl, val & 3);
+            break;
+        case BOARD_ID_EB:
+            /* The EB is the same except that there is no mux since
+             * the EB has a PL111.
+             */
+            s->sys_clcd &= 0x3f00;
+            s->sys_clcd |= val & ~0x3f00;
+            break;
+        case BOARD_ID_PBA8:
+        case BOARD_ID_PBX:
+            /* On PBA8 and PBX bit 7 is r/w and all other bits
+             * are either r/o or RAZ/WI.
+             */
+            s->sys_clcd &= (1 << 7);
+            s->sys_clcd |= val & ~(1 << 7);
+            break;
+        case BOARD_ID_VEXPRESS:
+        default:
+            /* On VExpress this register is unimplemented and will RAZ/WI */
+            break;
+        }
     case 0x54: /* CLCDSER */
     case 0x64: /* DMAPSR0 */
     case 0x68: /* DMAPSR1 */
@@ -334,7 +377,7 @@ static int arm_sysctl_init1(SysBusDevice *dev)
                                        DEVICE_NATIVE_ENDIAN);
     sysbus_init_mmio(dev, 0x1000, iomemtype);
     qdev_init_gpio_in(&s->busdev.qdev, arm_sysctl_gpio_set, 2);
-    /* ??? Save/restore.  */
+    qdev_init_gpio_out(&s->busdev.qdev, &s->pl110_mux_ctrl, 1);
     return 0;
 }