drivers/serial/serial_pic32.c

   1 /*
   2  * (c) 2015 Paul Thacker <paul.thacker@microchip.com>
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  *
   6  */
   7 #include <common.h>
   8 #include <clk.h>
   9 #include <dm.h>
  10 #include <serial.h>
  11 #include <wait_bit.h>
  12 #include <mach/pic32.h>
  13 #include <dt-bindings/clock/microchip,clock.h>
  14
  15 DECLARE_GLOBAL_DATA_PTR;
  16
  17 /* UART Control Registers */
  18 #define U_MOD           0x00
  19 #define U_MODCLR        (U_MOD + _CLR_OFFSET)
  20 #define U_MODSET        (U_MOD + _SET_OFFSET)
  21 #define U_STA           0x10
  22 #define U_STACLR        (U_STA + _CLR_OFFSET)
  23 #define U_STASET        (U_STA + _SET_OFFSET)
  24 #define U_TXR           0x20
  25 #define U_RXR           0x30
  26 #define U_BRG           0x40
  27
  28 /* U_MOD bits */
  29 #define UART_ENABLE             BIT(15)
  30
  31 /* U_STA bits */
  32 #define UART_RX_ENABLE          BIT(12)
  33 #define UART_TX_BRK             BIT(11)
  34 #define UART_TX_ENABLE          BIT(10)
  35 #define UART_TX_FULL            BIT(9)
  36 #define UART_TX_EMPTY           BIT(8)
  37 #define UART_RX_OVER            BIT(1)
  38 #define UART_RX_DATA_AVAIL      BIT(0)
  39
  40 struct pic32_uart_priv {
  41         void __iomem *base;
  42         ulong uartclk;
  43 };
  44
  45 /*
  46  * Initialize the serial port with the given baudrate.
  47  * The settings are always 8 data bits, no parity, 1 stop bit, no start bits.
  48  */
  49 static int pic32_serial_init(void __iomem *base, ulong clk, u32 baudrate)
  50 {
  51         u32 div = DIV_ROUND_CLOSEST(clk, baudrate * 16);
  52
  53         /* wait for TX FIFO to empty */
  54         wait_for_bit_le32(base + U_STA, UART_TX_EMPTY,
  55                           true, CONFIG_SYS_HZ, false);
  56
  57         /* send break */
  58         writel(UART_TX_BRK, base + U_STASET);
  59
  60         /* disable and clear mode */
  61         writel(0, base + U_MOD);
  62         writel(0, base + U_STA);
  63
  64         /* set baud rate generator */
  65         writel(div - 1, base + U_BRG);
  66
  67         /* enable the UART for TX and RX */
  68         writel(UART_TX_ENABLE | UART_RX_ENABLE, base + U_STASET);
  69
  70         /* enable the UART */
  71         writel(UART_ENABLE, base + U_MODSET);
  72         return 0;
  73 }
  74
  75 /* Check whether any char pending in RX fifo */
  76 static int pic32_uart_pending_input(void __iomem *base)
  77 {
  78         /* check if rx buffer overrun error has occurred */
  79         if (readl(base + U_STA) & UART_RX_OVER) {
  80                 readl(base + U_RXR);
  81
  82                 /* clear overrun error to keep receiving */
  83                 writel(UART_RX_OVER, base + U_STACLR);
  84         }
  85
  86         /* In PIC32 there is no way to know number of outstanding
  87          * chars in rx-fifo. Only it can be known whether there is any.
  88          */
  89         return readl(base + U_STA) & UART_RX_DATA_AVAIL;
  90 }
  91
  92 static int pic32_uart_pending(struct udevice *dev, bool input)
  93 {
  94         struct pic32_uart_priv *priv = dev_get_priv(dev);
  95
  96         if (input)
  97                 return pic32_uart_pending_input(priv->base);
  98
  99         return !(readl(priv->base + U_STA) & UART_TX_EMPTY);
 100 }
 101
 102 static int pic32_uart_setbrg(struct udevice *dev, int baudrate)
 103 {
 104         struct pic32_uart_priv *priv = dev_get_priv(dev);
 105
 106         return pic32_serial_init(priv->base, priv->uartclk, baudrate);
 107 }
 108
 109 static int pic32_uart_putc(struct udevice *dev, const char ch)
 110 {
 111         struct pic32_uart_priv *priv = dev_get_priv(dev);
 112
 113         /* Check if Tx FIFO is full */
 114         if (readl(priv->base + U_STA) & UART_TX_FULL)
 115                 return -EAGAIN;
 116
 117         /* pump the char to tx buffer */
 118         writel(ch, priv->base + U_TXR);
 119
 120         return 0;
 121 }
 122
 123 static int pic32_uart_getc(struct udevice *dev)
 124 {
 125         struct pic32_uart_priv *priv = dev_get_priv(dev);
 126
 127         /* return error if RX fifo is empty */
 128         if (!pic32_uart_pending_input(priv->base))
 129                 return -EAGAIN;
 130
 131         /* read the character from rx buffer */
 132         return readl(priv->base + U_RXR) & 0xff;
 133 }
 134
 135 static int pic32_uart_probe(struct udevice *dev)
 136 {
 137         struct pic32_uart_priv *priv = dev_get_priv(dev);
 138         struct clk clk;
 139         fdt_addr_t addr;
 140         fdt_size_t size;
 141         int ret;
 142
 143         /* get address */
 144         addr = fdtdec_get_addr_size(gd->fdt_blob, dev_of_offset(dev), "reg",
 145                                     &size);
 146         if (addr == FDT_ADDR_T_NONE)
 147                 return -EINVAL;
 148
 149         priv->base = ioremap(addr, size);
 150
 151         /* get clock rate */
 152         ret = clk_get_by_index(dev, 0, &clk);
 153         if (ret < 0)
 154                 return ret;
 155         priv->uartclk = clk_get_rate(&clk);
 156         clk_free(&clk);
 157
 158         /* initialize serial */
 159         return pic32_serial_init(priv->base, priv->uartclk, CONFIG_BAUDRATE);
 160 }
 161
 162 static const struct dm_serial_ops pic32_uart_ops = {
 163         .putc           = pic32_uart_putc,
 164         .pending        = pic32_uart_pending,
 165         .getc           = pic32_uart_getc,
 166         .setbrg         = pic32_uart_setbrg,
 167 };
 168
 169 static const struct udevice_id pic32_uart_ids[] = {
 170         { .compatible = "microchip,pic32mzda-uart" },
 171         {}
 172 };
 173
 174 U_BOOT_DRIVER(pic32_serial) = {
 175         .name           = "pic32-uart",
 176         .id             = UCLASS_SERIAL,
 177         .of_match       = pic32_uart_ids,
 178         .probe          = pic32_uart_probe,
 179         .ops            = &pic32_uart_ops,
 180         .flags          = DM_FLAG_PRE_RELOC,
 181         .priv_auto_alloc_size = sizeof(struct pic32_uart_priv),
 182 };
 183
 184 #ifdef CONFIG_DEBUG_UART_PIC32
 185 #include <debug_uart.h>
 186
 187 static inline void _debug_uart_init(void)
 188 {
 189         void __iomem *base = (void __iomem *)CONFIG_DEBUG_UART_BASE;
 190
 191         pic32_serial_init(base, CONFIG_DEBUG_UART_CLOCK, CONFIG_BAUDRATE);
 192 }
 193
 194 static inline void _debug_uart_putc(int ch)
 195 {
 196         writel(ch, CONFIG_DEBUG_UART_BASE + U_TXR);
 197 }
 198
 199 DEBUG_UART_FUNCS
 200 #endif