arm: xilinx_zynq: Add linux pre-boot

Add a Linux-specific pre-boot routine that matches the device-
specific bootloaders behaviour. This is needed for modern Linux that
expects the ARM PLL in SLCR to be a more even value (not 26).

Cc: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NPeter Crosthwaite <crosthwaite.peter@gmail.com>
Message-id: 9a9025ea65572586b50dca4e5819032e3c436d64.1446182614.git.crosthwaite.peter@gmail.com
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/arm/xilinx_zynq.c

@@ -43,6 +43,45 @@ static const int dma_irqs[8] = {
     46, 47, 48, 49, 72, 73, 74, 75
 };
 
+#define BOARD_SETUP_ADDR        0x100
+
+#define SLCR_LOCK_OFFSET        0x004
+#define SLCR_UNLOCK_OFFSET      0x008
+#define SLCR_ARM_PLL_OFFSET     0x100
+
+#define SLCR_XILINX_UNLOCK_KEY  0xdf0d
+#define SLCR_XILINX_LOCK_KEY    0x767b
+
+#define ARMV7_IMM16(x) (extract32((x),  0, 12) | \
+                        extract32((x), 12,  4) << 16)
+
+/* Write immediate val to address r0 + addr. r0 should contain base offset
+ * of the SLCR block. Clobbers r1.
+ */
+
+#define SLCR_WRITE(addr, val) \
+    0xe3001000 + ARMV7_IMM16(extract32((val),  0, 16)), /* movw r1 ... */ \
+    0xe3401000 + ARMV7_IMM16(extract32((val), 16, 16)), /* movt r1 ... */ \
+    0xe5801000 + (addr)
+
+static void zynq_write_board_setup(ARMCPU *cpu,
+                                   const struct arm_boot_info *info)
+{
+    int n;
+    uint32_t board_setup_blob[] = {
+        0xe3a004f8, /* mov r0, #0xf8000000 */
+        SLCR_WRITE(SLCR_UNLOCK_OFFSET, SLCR_XILINX_UNLOCK_KEY),
+        SLCR_WRITE(SLCR_ARM_PLL_OFFSET, 0x00014008),
+        SLCR_WRITE(SLCR_LOCK_OFFSET, SLCR_XILINX_LOCK_KEY),
+        0xe12fff1e, /* bx lr */
+    };
+    for (n = 0; n < ARRAY_SIZE(board_setup_blob); n++) {
+        board_setup_blob[n] = tswap32(board_setup_blob[n]);
+    }
+    rom_add_blob_fixed("board-setup", board_setup_blob,
+                       sizeof(board_setup_blob), BOARD_SETUP_ADDR);
+}
+
 static struct arm_boot_info zynq_binfo = {};
 
 static void gem_init(NICInfo *nd, uint32_t base, qemu_irq irq)
@@ -252,6 +291,9 @@ static void zynq_init(MachineState *machine)
     zynq_binfo.nb_cpus = 1;
     zynq_binfo.board_id = 0xd32;
     zynq_binfo.loader_start = 0;
+    zynq_binfo.board_setup_addr = BOARD_SETUP_ADDR;
+    zynq_binfo.write_board_setup = zynq_write_board_setup;
+
     arm_load_kernel(ARM_CPU(first_cpu), &zynq_binfo);
 }