x86: baytrail: Add SIO HS-UART clock setup

To support the BayTrail internal SIO HS UART, the internal UART clock
needs to get configured. This patch adds support for this clock
configuration which will be done, if the PCI device(s) are found.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/baytrail/cpu.c

@@ -9,12 +9,60 @@
 #include <common.h>
 #include <cpu.h>
 #include <dm.h>
+#include <pci.h>
 #include <asm/cpu.h>
 #include <asm/cpu_x86.h>
+#include <asm/io.h>
 #include <asm/lapic.h>
 #include <asm/msr.h>
 #include <asm/turbo.h>
 
+#define BYT_PRV_CLK			0x800
+#define BYT_PRV_CLK_EN			(1 << 0)
+#define BYT_PRV_CLK_M_VAL_SHIFT		1
+#define BYT_PRV_CLK_N_VAL_SHIFT		16
+#define BYT_PRV_CLK_UPDATE		(1 << 31)
+
+static void hsuart_clock_set(void *base)
+{
+	u32 m, n, reg;
+
+	/*
+	 * Configure the BayTrail UART clock for the internal HS UARTs
+	 * (PCI devices) to 58982400 Hz
+	 */
+	m = 0x2400;
+	n = 0x3d09;
+	reg = (m << BYT_PRV_CLK_M_VAL_SHIFT) | (n << BYT_PRV_CLK_N_VAL_SHIFT);
+	writel(reg, base + BYT_PRV_CLK);
+	reg |= BYT_PRV_CLK_EN | BYT_PRV_CLK_UPDATE;
+	writel(reg, base + BYT_PRV_CLK);
+}
+
+/*
+ * Configure the internal clock of both SIO HS-UARTs, if they are enabled
+ * via FSP
+ */
+int arch_cpu_init_dm(void)
+{
+	struct udevice *dev;
+	void *base;
+	int ret;
+	int i;
+
+	/* Loop over the 2 HS-UARTs */
+	for (i = 0; i < 2; i++) {
+		ret = dm_pci_bus_find_bdf(PCI_BDF(0, 0x1e, 3 + i), &dev);
+		if (!ret) {
+			base = dm_pci_map_bar(dev, PCI_BASE_ADDRESS_0,
+					      PCI_REGION_MEM);
+			hsuart_clock_set(base);
+		}
+	}
+
+	return 0;
+}
+
 static void set_max_freq(void)
 {
 	msr_t perf_ctl;