x86: apl: Add UART driver

Add a driver for the Apollo Lake UART. It uses the standard ns16550 device
but also sets up the input clock with LPSS and supports configuration via
of-platdata.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/apollolake/Makefile

@@ -3,3 +3,4 @@
 # Copyright 2019 Google LLC
 
 obj-y += pmc.o
+obj-y += uart.o

arch/x86/cpu/apollolake/uart.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Special driver to handle of-platdata
+ *
+ * Copyright 2019 Google LLC
+ *
+ * Some code from coreboot lpss.c
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dt-structs.h>
+#include <ns16550.h>
+#include <spl.h>
+#include <asm/io.h>
+#include <asm/pci.h>
+#include <asm/lpss.h>
+
+/* Low-power Subsystem (LPSS) clock register */
+enum {
+	LPSS_CLOCK_CTL_REG	= 0x200,
+	LPSS_CNT_CLOCK_EN	= 1,
+	LPSS_CNT_CLK_UPDATE	= 1U << 31,
+	LPSS_CLOCK_DIV_N_SHIFT	= 16,
+	LPSS_CLOCK_DIV_N_MASK	= 0x7fff << LPSS_CLOCK_DIV_N_SHIFT,
+	LPSS_CLOCK_DIV_M_SHIFT	= 1,
+	LPSS_CLOCK_DIV_M_MASK	= 0x7fff << LPSS_CLOCK_DIV_M_SHIFT,
+
+	/* These set the UART input clock speed */
+	LPSS_UART_CLK_M_VAL	= 0x25a,
+	LPSS_UART_CLK_N_VAL	= 0x7fff,
+};
+
+static void lpss_clk_update(void *regs, u32 clk_m_val, u32 clk_n_val)
+{
+	u32 clk_sel;
+
+	clk_sel = clk_n_val << LPSS_CLOCK_DIV_N_SHIFT |
+		 clk_m_val << LPSS_CLOCK_DIV_M_SHIFT;
+	clk_sel |= LPSS_CNT_CLK_UPDATE | LPSS_CNT_CLOCK_EN;
+
+	writel(clk_sel, regs + LPSS_CLOCK_CTL_REG);
+}
+
+static void uart_lpss_init(void *regs)
+{
+	/* Take UART out of reset */
+	lpss_reset_release(regs);
+
+	/* Set M and N divisor inputs and enable clock */
+	lpss_clk_update(regs, LPSS_UART_CLK_M_VAL, LPSS_UART_CLK_N_VAL);
+}
+
+void apl_uart_init(pci_dev_t bdf, ulong base)
+{
+	/* Set UART base address */
+	pci_x86_write_config(bdf, PCI_BASE_ADDRESS_0, base, PCI_SIZE_32);
+
+	/* Enable memory access and bus master */
+	pci_x86_write_config(bdf, PCI_COMMAND, PCI_COMMAND_MEMORY |
+			     PCI_COMMAND_MASTER, PCI_SIZE_32);
+
+	uart_lpss_init((void *)base);
+}
+
+/*
+ * This driver uses its own compatible string but almost everything else from
+ * the standard ns16550 driver. This allows us to provide an of-platdata
+ * implementation, since the platdata produced by of-platdata does not match
+ * struct ns16550_platdata.
+ *
+ * When running with of-platdata (generally TPL), the platdata is converted to
+ * something that ns16550 expects. When running withoutof-platdata (SPL, U-Boot
+ * proper), we use ns16550's ofdata_to_platdata routine.
+ */
+
+static int apl_ns16550_probe(struct udevice *dev)
+{
+	struct ns16550_platdata *plat = dev_get_platdata(dev);
+
+	if (!CONFIG_IS_ENABLED(PCI))
+		apl_uart_init(plat->bdf, plat->base);
+
+	return ns16550_serial_probe(dev);
+}
+
+static int apl_ns16550_ofdata_to_platdata(struct udevice *dev)
+{
+#if CONFIG_IS_ENABLED(OF_PLATDATA)
+	struct dtd_intel_apl_ns16550 *dtplat = dev_get_platdata(dev);
+	struct ns16550_platdata *plat;
+
+	/*
+	 * Convert our platdata to the ns16550's platdata, so we can just use
+	 * that driver
+	 */
+	plat = malloc(sizeof(*plat));
+	if (!plat)
+		return -ENOMEM;
+	plat->base = dtplat->early_regs[0];
+	plat->reg_width = 1;
+	plat->reg_shift = dtplat->reg_shift;
+	plat->reg_offset = 0;
+	plat->clock = dtplat->clock_frequency;
+	plat->fcr = UART_FCR_DEFVAL;
+	plat->bdf = pci_ofplat_get_devfn(dtplat->reg[0]);
+	dev->platdata = plat;
+#else
+	int ret;
+
+	ret = ns16550_serial_ofdata_to_platdata(dev);
+	if (ret)
+		return ret;
+#endif /* OF_PLATDATA */
+
+	return 0;
+}
+
+static const struct udevice_id apl_ns16550_serial_ids[] = {
+	{ .compatible = "intel,apl-ns16550" },
+	{ },
+};
+
+U_BOOT_DRIVER(apl_ns16550) = {
+	.name	= "intel_apl_ns16550",
+	.id	= UCLASS_SERIAL,
+	.of_match = apl_ns16550_serial_ids,
+	.platdata_auto_alloc_size = sizeof(struct ns16550_platdata),
+	.priv_auto_alloc_size = sizeof(struct NS16550),
+	.ops	= &ns16550_serial_ops,
+	.ofdata_to_platdata = apl_ns16550_ofdata_to_platdata,
+	.probe = apl_ns16550_probe,
+};

arch/x86/include/asm/arch-apollolake/uart.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef _ASM_ARCH_UART_H
+#define _ASM_ARCH_UART_H
+
+/**
+ * apl_uart_init() - Set up the APL UART device and clock
+ *
+ * This enables the PCI device, sets up the MMIO region and turns on the clock
+ * using LPSS.
+ *
+ * The UART won't actually work unless the GPIO settings are correct and the
+ * signals actually exit the SoC. See board_debug_uart_init() for that.
+ */
+int apl_uart_init(pci_dev_t bdf, ulong base);
+
+#endif