drivers/serial/serial_bcm283x_mu.c

   1 /*
   2  * (C) Copyright 2016 Stephen Warren <swarren@wwwdotorg.org>
   3  *
   4  * Derived from pl01x code:
   5  *
   6  * (C) Copyright 2000
   7  * Rob Taylor, Flying Pig Systems. robt@flyingpig.com.
   8  *
   9  * (C) Copyright 2004
  10  * ARM Ltd.
  11  * Philippe Robin, <philippe.robin@arm.com>
  12  *
  13  * SPDX-License-Identifier:     GPL-2.0+
  14  */
  15
  16 /* Simple U-Boot driver for the BCM283x mini UART */
  17
  18 #include <common.h>
  19 #include <dm.h>
  20 #include <errno.h>
  21 #include <watchdog.h>
  22 #include <asm/gpio.h>
  23 #include <asm/io.h>
  24 #include <serial.h>
  25 #include <dm/platform_data/serial_bcm283x_mu.h>
  26 #include <dm/pinctrl.h>
  27 #include <linux/compiler.h>
  28
  29 struct bcm283x_mu_regs {
  30         u32 io;
  31         u32 iir;
  32         u32 ier;
  33         u32 lcr;
  34         u32 mcr;
  35         u32 lsr;
  36         u32 msr;
  37         u32 scratch;
  38         u32 cntl;
  39         u32 stat;
  40         u32 baud;
  41 };
  42
  43 #define BCM283X_MU_LCR_DATA_SIZE_8      3
  44
  45 #define BCM283X_MU_LSR_TX_IDLE          BIT(6)
  46 /* This actually means not full, but is named not empty in the docs */
  47 #define BCM283X_MU_LSR_TX_EMPTY         BIT(5)
  48 #define BCM283X_MU_LSR_RX_READY         BIT(0)
  49
  50 struct bcm283x_mu_priv {
  51         struct bcm283x_mu_regs *regs;
  52 };
  53
  54 static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
  55 {
  56         struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
  57         struct bcm283x_mu_priv *priv = dev_get_priv(dev);
  58         struct bcm283x_mu_regs *regs = priv->regs;
  59         u32 divider;
  60
  61         if (plat->skip_init)
  62                 return 0;
  63
  64         divider = plat->clock / (baudrate * 8);
  65
  66         writel(BCM283X_MU_LCR_DATA_SIZE_8, &regs->lcr);
  67         writel(divider - 1, &regs->baud);
  68
  69         return 0;
  70 }
  71
  72 static int bcm283x_mu_serial_probe(struct udevice *dev)
  73 {
  74         struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
  75         struct bcm283x_mu_priv *priv = dev_get_priv(dev);
  76
  77         priv->regs = (struct bcm283x_mu_regs *)plat->base;
  78
  79         return 0;
  80 }
  81
  82 static int bcm283x_mu_serial_getc(struct udevice *dev)
  83 {
  84         struct bcm283x_mu_priv *priv = dev_get_priv(dev);
  85         struct bcm283x_mu_regs *regs = priv->regs;
  86         u32 data;
  87
  88         /* Wait until there is data in the FIFO */
  89         if (!(readl(&regs->lsr) & BCM283X_MU_LSR_RX_READY))
  90                 return -EAGAIN;
  91
  92         data = readl(&regs->io);
  93
  94         return (int)data;
  95 }
  96
  97 static int bcm283x_mu_serial_putc(struct udevice *dev, const char data)
  98 {
  99         struct bcm283x_mu_priv *priv = dev_get_priv(dev);
 100         struct bcm283x_mu_regs *regs = priv->regs;
 101
 102         /* Wait until there is space in the FIFO */
 103         if (!(readl(&regs->lsr) & BCM283X_MU_LSR_TX_EMPTY))
 104                 return -EAGAIN;
 105
 106         /* Send the character */
 107         writel(data, &regs->io);
 108
 109         return 0;
 110 }
 111
 112 static int bcm283x_mu_serial_pending(struct udevice *dev, bool input)
 113 {
 114         struct bcm283x_mu_priv *priv = dev_get_priv(dev);
 115         struct bcm283x_mu_regs *regs = priv->regs;
 116         unsigned int lsr;
 117
 118         lsr = readl(&regs->lsr);
 119
 120         if (input) {
 121                 WATCHDOG_RESET();
 122                 return (lsr & BCM283X_MU_LSR_RX_READY) ? 1 : 0;
 123         } else {
 124                 return (lsr & BCM283X_MU_LSR_TX_IDLE) ? 0 : 1;
 125         }
 126 }
 127
 128 static const struct dm_serial_ops bcm283x_mu_serial_ops = {
 129         .putc = bcm283x_mu_serial_putc,
 130         .pending = bcm283x_mu_serial_pending,
 131         .getc = bcm283x_mu_serial_getc,
 132         .setbrg = bcm283x_mu_serial_setbrg,
 133 };
 134
 135 #if CONFIG_IS_ENABLED(OF_CONTROL)
 136 static const struct udevice_id bcm283x_mu_serial_id[] = {
 137         {.compatible = "brcm,bcm2835-aux-uart"},
 138         {}
 139 };
 140
 141 /*
 142  * Check if this serial device is muxed
 143  *
 144  * The serial device will only work properly if it has been muxed to the serial
 145  * pins by firmware. Check whether that happened here.
 146  *
 147  * @return true if serial device is muxed, false if not
 148  */
 149 static bool bcm283x_is_serial_muxed(void)
 150 {
 151         int serial_gpio = 15;
 152         struct udevice *dev;
 153
 154         if (uclass_first_device(UCLASS_PINCTRL, &dev) || !dev)
 155                 return false;
 156
 157         if (pinctrl_get_gpio_mux(dev, 0, serial_gpio) != BCM2835_GPIO_ALT5)
 158                 return false;
 159
 160         return true;
 161 }
 162
 163 static int bcm283x_mu_serial_ofdata_to_platdata(struct udevice *dev)
 164 {
 165         struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
 166         fdt_addr_t addr;
 167
 168         /* Don't spawn the device if it's not muxed */
 169         if (!bcm283x_is_serial_muxed())
 170                 return -ENODEV;
 171
 172         addr = devfdt_get_addr(dev);
 173         if (addr == FDT_ADDR_T_NONE)
 174                 return -EINVAL;
 175
 176         plat->base = addr;
 177         plat->clock = dev_read_u32_default(dev, "clock", 1);
 178
 179         /*
 180          * TODO: Reinitialization doesn't always work for now, just skip
 181          *       init always - we know we're already initialized
 182          */
 183         plat->skip_init = true;
 184
 185         return 0;
 186 }
 187 #endif
 188
 189 U_BOOT_DRIVER(serial_bcm283x_mu) = {
 190         .name = "serial_bcm283x_mu",
 191         .id = UCLASS_SERIAL,
 192         .of_match = of_match_ptr(bcm283x_mu_serial_id),
 193         .ofdata_to_platdata = of_match_ptr(bcm283x_mu_serial_ofdata_to_platdata),
 194         .platdata_auto_alloc_size = sizeof(struct bcm283x_mu_serial_platdata),
 195         .probe = bcm283x_mu_serial_probe,
 196         .ops = &bcm283x_mu_serial_ops,
 197         .flags = DM_FLAG_PRE_RELOC,
 198         .priv_auto_alloc_size = sizeof(struct bcm283x_mu_priv),
 199 };