sunxi: Support booting from SPI flash

Allwinner devices support SPI flash as one of the possible
bootable media type. The SPI flash chip needs to be connected
to SPI0 pins (port C) to make this work. More information is
available at:

    https://linux-sunxi.org/Bootable_SPI_flash

This patch adds the initial support for booting from SPI flash.
The existing SPI frameworks are not used in order to reduce the
SPL code size. Right now the SPL size grows by ~370 bytes when
CONFIG_SPL_SPI_SUNXI option is enabled.

While there are no popular Allwinner devices with SPI flash at
the moment, testing can be done using a SPI flash module (it
can be bought for ~2$ on ebay) and jumper wires with the boards,
which expose relevant pins on the expansion header. The SPI flash
chips themselves are very cheap (some prices are even listed as
low as 4 cents) and should not cost much if somebody decides to
design a development board with an SPI flash chip soldered on
the PCB.

Another nice feature of the SPI flash is that it can be safely
accessed in a device-independent way (since we know that the
boot ROM is already probing these pins during the boot time).
And if, for example, Olimex boards opted to use SPI flash instead
of EEPROM, then they would have been able to have U-Boot installed
in the SPI flash now and boot the rest of the system from the SATA
hard drive. Hopefully we may see new interesting Allwinner based
development boards in the future, now that the software support
for the SPI flash is in a better shape :-)

Testing can be done by enabling the CONFIG_SPL_SPI_SUNXI option
in a board defconfig, then building U-Boot and finally flashing
the resulting u-boot-sunxi-with-spl.bin binary over USB OTG with
a help of the sunxi-fel tool:

   sunxi-fel spiflash-write 0 u-boot-sunxi-with-spl.bin

The device needs to be switched into FEL (USB recovery) mode first.
The most suitable boards for testing are Orange Pi PC and Pine64.
Because these boards are cheap, have no built-in NAND/eMMC and
expose SPI0 pins on the Raspberry Pi compatible expansion header.
The A13-OLinuXino-Micro board also can be used.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

3 files changed, 296 insertions, 0 deletions

diff --git a/drivers/mtd/spi/Kconfig b/drivers/mtd/spi/Kconfig
index 3f7433c..1f23c8e 100644
--- a/drivers/mtd/spi/Kconfig
+++ b/drivers/mtd/spi/Kconfig
@@ -128,4 +128,16 @@ config SPI_FLASH_MTD
 
 	  If unsure, say N
 
+if SPL
+
+config SPL_SPI_SUNXI
+	bool "Support for SPI Flash on Allwinner SoCs in SPL"
+	depends on MACH_SUN4I || MACH_SUN5I || MACH_SUN7I || MACH_SUN8I_H3 || MACH_SUN50I
+	---help---
+	Enable support for SPI Flash. This option allows SPL to read from
+	sunxi SPI Flash. It uses the same method as the boot ROM, so does
+	not need any extra configuration.
+
+endif
+
 endmenu # menu "SPI Flash Support"
diff --git a/drivers/mtd/spi/Makefile b/drivers/mtd/spi/Makefile
index c665836..6f47a66 100644
--- a/drivers/mtd/spi/Makefile
+++ b/drivers/mtd/spi/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_DM_SPI_FLASH) += sf-uclass.o
 ifdef CONFIG_SPL_BUILD
 obj-$(CONFIG_SPL_SPI_LOAD)	+= spi_spl_load.o
 obj-$(CONFIG_SPL_SPI_BOOT)	+= fsl_espi_spl.o
+obj-$(CONFIG_SPL_SPI_SUNXI)	+= sunxi_spi_spl.o
 endif
 
 obj-$(CONFIG_SPI_FLASH) += sf_probe.o spi_flash.o sf_params.o sf.o
diff --git a/drivers/mtd/spi/sunxi_spi_spl.c b/drivers/mtd/spi/sunxi_spi_spl.c
new file mode 100644
index 0000000..e3ded5b
--- /dev/null
+++ b/drivers/mtd/spi/sunxi_spi_spl.c
@@ -0,0 +1,283 @@
+/*
+ * Copyright (C) 2016 Siarhei Siamashka <siarhei.siamashka@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <spl.h>
+#include <asm/gpio.h>
+#include <asm/io.h>
+
+#ifdef CONFIG_SPL_OS_BOOT
+#error CONFIG_SPL_OS_BOOT is not supported yet
+#endif
+
+/*
+ * This is a very simple U-Boot image loading implementation, trying to
+ * replicate what the boot ROM is doing when loading the SPL. Because we
+ * know the exact pins where the SPI Flash is connected and also know
+ * that the Read Data Bytes (03h) command is supported, the hardware
+ * configuration is very simple and we don't need the extra flexibility
+ * of the SPI framework. Moreover, we rely on the default settings of
+ * the SPI controler hardware registers and only adjust what needs to
+ * be changed. This is good for the code size and this implementation
+ * adds less than 400 bytes to the SPL.
+ *
+ * There are two variants of the SPI controller in Allwinner SoCs:
+ * A10/A13/A20 (sun4i variant) and everything else (sun6i variant).
+ * Both of them are supported.
+ *
+ * The pin mixing part is SoC specific and only A10/A13/A20/H3/A64 are
+ * supported at the moment.
+ */
+
+/*****************************************************************************/
+/* SUN4I variant of the SPI controller                                       */
+/*****************************************************************************/
+
+#define SUN4I_SPI0_CCTL             (0x01C05000 + 0x1C)
+#define SUN4I_SPI0_CTL              (0x01C05000 + 0x08)
+#define SUN4I_SPI0_RX               (0x01C05000 + 0x00)
+#define SUN4I_SPI0_TX               (0x01C05000 + 0x04)
+#define SUN4I_SPI0_FIFO_STA         (0x01C05000 + 0x28)
+#define SUN4I_SPI0_BC               (0x01C05000 + 0x20)
+#define SUN4I_SPI0_TC               (0x01C05000 + 0x24)
+
+#define SUN4I_CTL_ENABLE            BIT(0)
+#define SUN4I_CTL_MASTER            BIT(1)
+#define SUN4I_CTL_TF_RST            BIT(8)
+#define SUN4I_CTL_RF_RST            BIT(9)
+#define SUN4I_CTL_XCH               BIT(10)
+
+/*****************************************************************************/
+/* SUN6I variant of the SPI controller                                       */
+/*****************************************************************************/
+
+#define SUN6I_SPI0_CCTL             (0x01C68000 + 0x24)
+#define SUN6I_SPI0_GCR              (0x01C68000 + 0x04)
+#define SUN6I_SPI0_TCR              (0x01C68000 + 0x08)
+#define SUN6I_SPI0_FIFO_STA         (0x01C68000 + 0x1C)
+#define SUN6I_SPI0_MBC              (0x01C68000 + 0x30)
+#define SUN6I_SPI0_MTC              (0x01C68000 + 0x34)
+#define SUN6I_SPI0_BCC              (0x01C68000 + 0x38)
+#define SUN6I_SPI0_TXD              (0x01C68000 + 0x200)
+#define SUN6I_SPI0_RXD              (0x01C68000 + 0x300)
+
+#define SUN6I_CTL_ENABLE            BIT(0)
+#define SUN6I_CTL_MASTER            BIT(1)
+#define SUN6I_CTL_SRST              BIT(31)
+#define SUN6I_TCR_XCH               BIT(31)
+
+/*****************************************************************************/
+
+#define CCM_AHB_GATING0             (0x01C20000 + 0x60)
+#define CCM_SPI0_CLK                (0x01C20000 + 0xA0)
+#define SUN6I_BUS_SOFT_RST_REG0     (0x01C20000 + 0x2C0)
+
+#define AHB_RESET_SPI0_SHIFT        20
+#define AHB_GATE_OFFSET_SPI0        20
+
+#define SPI0_CLK_DIV_BY_2           0x1000
+#define SPI0_CLK_DIV_BY_4           0x1001
+
+/*****************************************************************************/
+
+/*
+ * Allwinner A10/A20 SoCs were using pins PC0,PC1,PC2,PC23 for booting
+ * from SPI Flash, everything else is using pins PC0,PC1,PC2,PC3.
+ */
+static void spi0_pinmux_setup(unsigned int pin_function)
+{
+	unsigned int pin;
+
+	for (pin = SUNXI_GPC(0); pin <= SUNXI_GPC(2); pin++)
+		sunxi_gpio_set_cfgpin(pin, pin_function);
+
+	if (IS_ENABLED(CONFIG_MACH_SUN4I) || IS_ENABLED(CONFIG_MACH_SUN7I))
+		sunxi_gpio_set_cfgpin(SUNXI_GPC(23), pin_function);
+	else
+		sunxi_gpio_set_cfgpin(SUNXI_GPC(3), pin_function);
+}
+
+/*
+ * Setup 6 MHz from OSC24M (because the BROM is doing the same).
+ */
+static void spi0_enable_clock(void)
+{
+	/* Deassert SPI0 reset on SUN6I */
+	if (IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I))
+		setbits_le32(SUN6I_BUS_SOFT_RST_REG0,
+			     (1 << AHB_RESET_SPI0_SHIFT));
+
+	/* Open the SPI0 gate */
+	setbits_le32(CCM_AHB_GATING0, (1 << AHB_GATE_OFFSET_SPI0));
+
+	/* Divide by 4 */
+	writel(SPI0_CLK_DIV_BY_4, IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I) ?
+				  SUN6I_SPI0_CCTL : SUN4I_SPI0_CCTL);
+	/* 24MHz from OSC24M */
+	writel((1 << 31), CCM_SPI0_CLK);
+
+	if (IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I)) {
+		/* Enable SPI in the master mode and do a soft reset */
+		setbits_le32(SUN6I_SPI0_GCR, SUN6I_CTL_MASTER |
+					     SUN6I_CTL_ENABLE |
+					     SUN6I_CTL_SRST);
+		/* Wait for completion */
+		while (readl(SUN6I_SPI0_GCR) & SUN6I_CTL_SRST)
+			;
+	} else {
+		/* Enable SPI in the master mode and reset FIFO */
+		setbits_le32(SUN4I_SPI0_CTL, SUN4I_CTL_MASTER |
+					     SUN4I_CTL_ENABLE |
+					     SUN4I_CTL_TF_RST |
+					     SUN4I_CTL_RF_RST);
+	}
+}
+
+static void spi0_disable_clock(void)
+{
+	/* Disable the SPI0 controller */
+	if (IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I))
+		clrbits_le32(SUN6I_SPI0_GCR, SUN6I_CTL_MASTER |
+					     SUN6I_CTL_ENABLE);
+	else
+		clrbits_le32(SUN4I_SPI0_CTL, SUN4I_CTL_MASTER |
+					     SUN4I_CTL_ENABLE);
+
+	/* Disable the SPI0 clock */
+	writel(0, CCM_SPI0_CLK);
+
+	/* Close the SPI0 gate */
+	clrbits_le32(CCM_AHB_GATING0, (1 << AHB_GATE_OFFSET_SPI0));
+
+	/* Assert SPI0 reset on SUN6I */
+	if (IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I))
+		clrbits_le32(SUN6I_BUS_SOFT_RST_REG0,
+			     (1 << AHB_RESET_SPI0_SHIFT));
+}
+
+static int spi0_init(void)
+{
+	unsigned int pin_function = SUNXI_GPC_SPI0;
+	if (IS_ENABLED(CONFIG_MACH_SUN50I))
+		pin_function = SUN50I_GPC_SPI0;
+
+	spi0_pinmux_setup(pin_function);
+	spi0_enable_clock();
+}
+
+static void spi0_deinit(void)
+{
+	/* New SoCs can disable pins, older could only set them as input */
+	unsigned int pin_function = SUNXI_GPIO_INPUT;
+	if (IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I))
+		pin_function = SUNXI_GPIO_DISABLE;
+
+	spi0_disable_clock();
+	spi0_pinmux_setup(pin_function);
+}
+
+/*****************************************************************************/
+
+#define SPI_READ_MAX_SIZE 60 /* FIFO size, minus 4 bytes of the header */
+
+static void sunxi_spi0_read_data(u8 *buf, u32 addr, u32 bufsize,
+				 u32 spi_ctl_reg,
+				 u32 spi_ctl_xch_bitmask,
+				 u32 spi_fifo_reg,
+				 u32 spi_tx_reg,
+				 u32 spi_rx_reg,
+				 u32 spi_bc_reg,
+				 u32 spi_tc_reg,
+				 u32 spi_bcc_reg)
+{
+	writel(4 + bufsize, spi_bc_reg); /* Burst counter (total bytes) */
+	writel(4, spi_tc_reg);           /* Transfer counter (bytes to send) */
+	if (spi_bcc_reg)
+		writel(4, spi_bcc_reg);  /* SUN6I also needs this */
+
+	/* Send the Read Data Bytes (03h) command header */
+	writeb(0x03, spi_tx_reg);
+	writeb((u8)(addr >> 16), spi_tx_reg);
+	writeb((u8)(addr >> 8), spi_tx_reg);
+	writeb((u8)(addr), spi_tx_reg);
+
+	/* Start the data transfer */
+	setbits_le32(spi_ctl_reg, spi_ctl_xch_bitmask);
+
+	/* Wait until everything is received in the RX FIFO */
+	while ((readl(spi_fifo_reg) & 0x7F) < 4 + bufsize)
+		;
+
+	/* Skip 4 bytes */
+	readl(spi_rx_reg);
+
+	/* Read the data */
+	while (bufsize-- > 0)
+		*buf++ = readb(spi_rx_reg);
+
+	/* tSHSL time is up to 100 ns in various SPI flash datasheets */
+	udelay(1);
+}
+
+static void spi0_read_data(void *buf, u32 addr, u32 len)
+{
+	u8 *buf8 = buf;
+	u32 chunk_len;
+
+	while (len > 0) {
+		chunk_len = len;
+		if (chunk_len > SPI_READ_MAX_SIZE)
+			chunk_len = SPI_READ_MAX_SIZE;
+
+		if (IS_ENABLED(CONFIG_SUNXI_GEN_SUN6I)) {
+			sunxi_spi0_read_data(buf8, addr, chunk_len,
+					     SUN6I_SPI0_TCR,
+					     SUN6I_TCR_XCH,
+					     SUN6I_SPI0_FIFO_STA,
+					     SUN6I_SPI0_TXD,
+					     SUN6I_SPI0_RXD,
+					     SUN6I_SPI0_MBC,
+					     SUN6I_SPI0_MTC,
+					     SUN6I_SPI0_BCC);
+		} else {
+			sunxi_spi0_read_data(buf8, addr, chunk_len,
+					     SUN4I_SPI0_CTL,
+					     SUN4I_CTL_XCH,
+					     SUN4I_SPI0_FIFO_STA,
+					     SUN4I_SPI0_TX,
+					     SUN4I_SPI0_RX,
+					     SUN4I_SPI0_BC,
+					     SUN4I_SPI0_TC,
+					     0);
+		}
+
+		len  -= chunk_len;
+		buf8 += chunk_len;
+		addr += chunk_len;
+	}
+}
+
+/*****************************************************************************/
+
+int spl_spi_load_image(void)
+{
+	int err;
+	struct image_header *header;
+	header = (struct image_header *)(CONFIG_SYS_TEXT_BASE);
+
+	spi0_init();
+
+	spi0_read_data((void *)header, CONFIG_SYS_SPI_U_BOOT_OFFS, 0x40);
+	err = spl_parse_image_header(header);
+	if (err)
+		return err;
+
+	spi0_read_data((void *)spl_image.load_addr, CONFIG_SYS_SPI_U_BOOT_OFFS,
+		       spl_image.size);
+
+	spi0_deinit();
+	return 0;
+}