drivers/tty/serial/8250/8250_dwlib.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /* Synopsys DesignWare 8250 library. */
   3
   4 #include <linux/bitops.h>
   5 #include <linux/device.h>
   6 #include <linux/io.h>
   7 #include <linux/kernel.h>
   8 #include <linux/serial_8250.h>
   9 #include <linux/serial_core.h>
  10
  11 #include "8250_dwlib.h"
  12
  13 /* Offsets for the DesignWare specific registers */
  14 #define DW_UART_DLF     0xc0 /* Divisor Latch Fraction Register */
  15 #define DW_UART_CPR     0xf4 /* Component Parameter Register */
  16 #define DW_UART_UCV     0xf8 /* UART Component Version */
  17
  18 /* Component Parameter Register bits */
  19 #define DW_UART_CPR_ABP_DATA_WIDTH      (3 << 0)
  20 #define DW_UART_CPR_AFCE_MODE           (1 << 4)
  21 #define DW_UART_CPR_THRE_MODE           (1 << 5)
  22 #define DW_UART_CPR_SIR_MODE            (1 << 6)
  23 #define DW_UART_CPR_SIR_LP_MODE         (1 << 7)
  24 #define DW_UART_CPR_ADDITIONAL_FEATURES (1 << 8)
  25 #define DW_UART_CPR_FIFO_ACCESS         (1 << 9)
  26 #define DW_UART_CPR_FIFO_STAT           (1 << 10)
  27 #define DW_UART_CPR_SHADOW              (1 << 11)
  28 #define DW_UART_CPR_ENCODED_PARMS       (1 << 12)
  29 #define DW_UART_CPR_DMA_EXTRA           (1 << 13)
  30 #define DW_UART_CPR_FIFO_MODE           (0xff << 16)
  31
  32 /* Helper for FIFO size calculation */
  33 #define DW_UART_CPR_FIFO_SIZE(a)        (((a >> 16) & 0xff) * 16)
  34
  35 static inline u32 dw8250_readl_ext(struct uart_port *p, int offset)
  36 {
  37         if (p->iotype == UPIO_MEM32BE)
  38                 return ioread32be(p->membase + offset);
  39         return readl(p->membase + offset);
  40 }
  41
  42 static inline void dw8250_writel_ext(struct uart_port *p, int offset, u32 reg)
  43 {
  44         if (p->iotype == UPIO_MEM32BE)
  45                 iowrite32be(reg, p->membase + offset);
  46         else
  47                 writel(reg, p->membase + offset);
  48 }
  49
  50 /*
  51  * divisor = div(I) + div(F)
  52  * "I" means integer, "F" means fractional
  53  * quot = div(I) = clk / (16 * baud)
  54  * frac = div(F) * 2^dlf_size
  55  *
  56  * let rem = clk % (16 * baud)
  57  * we have: div(F) * (16 * baud) = rem
  58  * so frac = 2^dlf_size * rem / (16 * baud) = (rem << dlf_size) / (16 * baud)
  59  */
  60 static unsigned int dw8250_get_divisor(struct uart_port *p, unsigned int baud,
  61                                        unsigned int *frac)
  62 {
  63         unsigned int quot, rem, base_baud = baud * 16;
  64         struct dw8250_port_data *d = p->private_data;
  65
  66         quot = p->uartclk / base_baud;
  67         rem = p->uartclk % base_baud;
  68         *frac = DIV_ROUND_CLOSEST(rem << d->dlf_size, base_baud);
  69
  70         return quot;
  71 }
  72
  73 static void dw8250_set_divisor(struct uart_port *p, unsigned int baud,
  74                                unsigned int quot, unsigned int quot_frac)
  75 {
  76         dw8250_writel_ext(p, DW_UART_DLF, quot_frac);
  77         serial8250_do_set_divisor(p, baud, quot, quot_frac);
  78 }
  79
  80 void dw8250_setup_port(struct uart_port *p)
  81 {
  82         struct uart_8250_port *up = up_to_u8250p(p);
  83         u32 reg;
  84
  85         /*
  86          * If the Component Version Register returns zero, we know that
  87          * ADDITIONAL_FEATURES are not enabled. No need to go any further.
  88          */
  89         reg = dw8250_readl_ext(p, DW_UART_UCV);
  90         if (!reg)
  91                 return;
  92
  93         dev_dbg(p->dev, "Designware UART version %c.%c%c\n",
  94                 (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
  95
  96         dw8250_writel_ext(p, DW_UART_DLF, ~0U);
  97         reg = dw8250_readl_ext(p, DW_UART_DLF);
  98         dw8250_writel_ext(p, DW_UART_DLF, 0);
  99
 100         if (reg) {
 101                 struct dw8250_port_data *d = p->private_data;
 102
 103                 d->dlf_size = fls(reg);
 104                 p->get_divisor = dw8250_get_divisor;
 105                 p->set_divisor = dw8250_set_divisor;
 106         }
 107
 108         reg = dw8250_readl_ext(p, DW_UART_CPR);
 109         if (!reg)
 110                 return;
 111
 112         /* Select the type based on FIFO */
 113         if (reg & DW_UART_CPR_FIFO_MODE) {
 114                 p->type = PORT_16550A;
 115                 p->flags |= UPF_FIXED_TYPE;
 116                 p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
 117                 up->capabilities = UART_CAP_FIFO;
 118         }
 119
 120         if (reg & DW_UART_CPR_AFCE_MODE)
 121                 up->capabilities |= UART_CAP_AFE;
 122
 123         if (reg & DW_UART_CPR_SIR_MODE)
 124                 up->capabilities |= UART_CAP_IRDA;
 125 }
 126 EXPORT_SYMBOL_GPL(dw8250_setup_port);