+/* Tornado-specific constants for the TCR and CPR registers; see below. */
+#define OXSEMI_TORNADO_TCR_MASK 0xf
+#define OXSEMI_TORNADO_CPR_MASK 0x1ff
+#define OXSEMI_TORNADO_CPR_MIN 0x008
+#define OXSEMI_TORNADO_CPR_DEF 0x10f
+
+/*
+ * Determine the oversampling rate, the clock prescaler, and the clock
+ * divisor for the requested baud rate. The clock rate is 62.5 MHz,
+ * which is four times the baud base, and the prescaler increments in
+ * steps of 1/8. Therefore to make calculations on integers we need
+ * to use a scaled clock rate, which is the baud base multiplied by 32
+ * (or our assumed UART clock rate multiplied by 2).
+ *
+ * The allowed oversampling rates are from 4 up to 16 inclusive (values
+ * from 0 to 3 inclusive map to 16). Likewise the clock prescaler allows
+ * values between 1.000 and 63.875 inclusive (operation for values from
+ * 0.000 to 0.875 has not been specified). The clock divisor is the usual
+ * unsigned 16-bit integer.
+ *
+ * For the most accurate baud rate we use a table of predetermined
+ * oversampling rates and clock prescalers that records all possible
+ * products of the two parameters in the range from 4 up to 255 inclusive,
+ * and additionally 335 for the 1500000bps rate, with the prescaler scaled
+ * by 8. The table is sorted by the decreasing value of the oversampling
+ * rate and ties are resolved by sorting by the decreasing value of the
+ * product. This way preference is given to higher oversampling rates.
+ *
+ * We iterate over the table and choose the product of an oversampling
+ * rate and a clock prescaler that gives the lowest integer division
+ * result deviation, or if an exact integer divider is found we stop
+ * looking for it right away. We do some fixup if the resulting clock
+ * divisor required would be out of its unsigned 16-bit integer range.
+ *
+ * Finally we abuse the supposed fractional part returned to encode the
+ * 4-bit value of the oversampling rate and the 9-bit value of the clock
+ * prescaler which will end up in the TCR and CPR/CPR2 registers.
+ */
+static unsigned int pci_oxsemi_tornado_get_divisor(struct uart_port *port,
+ unsigned int baud,
+ unsigned int *frac)
+{
+ static u8 p[][2] = {
+ { 16, 14, }, { 16, 13, }, { 16, 12, }, { 16, 11, },
+ { 16, 10, }, { 16, 9, }, { 16, 8, }, { 15, 17, },
+ { 15, 16, }, { 15, 15, }, { 15, 14, }, { 15, 13, },
+ { 15, 12, }, { 15, 11, }, { 15, 10, }, { 15, 9, },
+ { 15, 8, }, { 14, 18, }, { 14, 17, }, { 14, 14, },
+ { 14, 13, }, { 14, 12, }, { 14, 11, }, { 14, 10, },
+ { 14, 9, }, { 14, 8, }, { 13, 19, }, { 13, 18, },
+ { 13, 17, }, { 13, 13, }, { 13, 12, }, { 13, 11, },
+ { 13, 10, }, { 13, 9, }, { 13, 8, }, { 12, 19, },
+ { 12, 18, }, { 12, 17, }, { 12, 11, }, { 12, 9, },
+ { 12, 8, }, { 11, 23, }, { 11, 22, }, { 11, 21, },
+ { 11, 20, }, { 11, 19, }, { 11, 18, }, { 11, 17, },
+ { 11, 11, }, { 11, 10, }, { 11, 9, }, { 11, 8, },
+ { 10, 25, }, { 10, 23, }, { 10, 20, }, { 10, 19, },
+ { 10, 17, }, { 10, 10, }, { 10, 9, }, { 10, 8, },
+ { 9, 27, }, { 9, 23, }, { 9, 21, }, { 9, 19, },
+ { 9, 18, }, { 9, 17, }, { 9, 9, }, { 9, 8, },
+ { 8, 31, }, { 8, 29, }, { 8, 23, }, { 8, 19, },
+ { 8, 17, }, { 8, 8, }, { 7, 35, }, { 7, 31, },
+ { 7, 29, }, { 7, 25, }, { 7, 23, }, { 7, 21, },
+ { 7, 19, }, { 7, 17, }, { 7, 15, }, { 7, 14, },
+ { 7, 13, }, { 7, 12, }, { 7, 11, }, { 7, 10, },
+ { 7, 9, }, { 7, 8, }, { 6, 41, }, { 6, 37, },
+ { 6, 31, }, { 6, 29, }, { 6, 23, }, { 6, 19, },
+ { 6, 17, }, { 6, 13, }, { 6, 11, }, { 6, 10, },
+ { 6, 9, }, { 6, 8, }, { 5, 67, }, { 5, 47, },
+ { 5, 43, }, { 5, 41, }, { 5, 37, }, { 5, 31, },
+ { 5, 29, }, { 5, 25, }, { 5, 23, }, { 5, 19, },
+ { 5, 17, }, { 5, 15, }, { 5, 13, }, { 5, 11, },
+ { 5, 10, }, { 5, 9, }, { 5, 8, }, { 4, 61, },
+ { 4, 59, }, { 4, 53, }, { 4, 47, }, { 4, 43, },
+ { 4, 41, }, { 4, 37, }, { 4, 31, }, { 4, 29, },
+ { 4, 23, }, { 4, 19, }, { 4, 17, }, { 4, 13, },
+ { 4, 9, }, { 4, 8, },
+ };
+ /* Scale the quotient for comparison to get the fractional part. */
+ const unsigned int quot_scale = 65536;
+ unsigned int sclk = port->uartclk * 2;
+ unsigned int sdiv = DIV_ROUND_CLOSEST(sclk, baud);
+ unsigned int best_squot;
+ unsigned int squot;
+ unsigned int quot;
+ u16 cpr;
+ u8 tcr;
+ int i;
+
+ /* Old custom speed handling. */
+ if (baud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST) {
+ unsigned int cust_div = port->custom_divisor;
+
+ quot = cust_div & UART_DIV_MAX;
+ tcr = (cust_div >> 16) & OXSEMI_TORNADO_TCR_MASK;
+ cpr = (cust_div >> 20) & OXSEMI_TORNADO_CPR_MASK;
+ if (cpr < OXSEMI_TORNADO_CPR_MIN)
+ cpr = OXSEMI_TORNADO_CPR_DEF;
+ } else {
+ best_squot = quot_scale;
+ for (i = 0; i < ARRAY_SIZE(p); i++) {
+ unsigned int spre;
+ unsigned int srem;
+ u8 cp;
+ u8 tc;
+
+ tc = p[i][0];
+ cp = p[i][1];
+ spre = tc * cp;
+
+ srem = sdiv % spre;
+ if (srem > spre / 2)
+ srem = spre - srem;
+ squot = DIV_ROUND_CLOSEST(srem * quot_scale, spre);
+
+ if (srem == 0) {
+ tcr = tc;
+ cpr = cp;
+ quot = sdiv / spre;
+ break;
+ } else if (squot < best_squot) {
+ best_squot = squot;
+ tcr = tc;
+ cpr = cp;
+ quot = DIV_ROUND_CLOSEST(sdiv, spre);
+ }
+ }
+ while (tcr <= (OXSEMI_TORNADO_TCR_MASK + 1) >> 1 &&
+ quot % 2 == 0) {
+ quot >>= 1;
+ tcr <<= 1;
+ }
+ while (quot > UART_DIV_MAX) {
+ if (tcr <= (OXSEMI_TORNADO_TCR_MASK + 1) >> 1) {
+ quot >>= 1;
+ tcr <<= 1;
+ } else if (cpr <= OXSEMI_TORNADO_CPR_MASK >> 1) {
+ quot >>= 1;
+ cpr <<= 1;
+ } else {
+ quot = quot * cpr / OXSEMI_TORNADO_CPR_MASK;
+ cpr = OXSEMI_TORNADO_CPR_MASK;
+ }
+ }
+ }
+
+ *frac = (cpr << 8) | (tcr & OXSEMI_TORNADO_TCR_MASK);
+ return quot;
+}
+
+/*
+ * Set the oversampling rate in the transmitter clock cycle register (TCR),
+ * the clock prescaler in the clock prescaler register (CPR and CPR2), and
+ * the clock divisor in the divisor latch (DLL and DLM). Note that for
+ * backwards compatibility any write to CPR clears CPR2 and therefore CPR
+ * has to be written first, followed by CPR2, which occupies the location
+ * of CKS used with earlier UART designs.
+ */
+static void pci_oxsemi_tornado_set_divisor(struct uart_port *port,
+ unsigned int baud,
+ unsigned int quot,
+ unsigned int quot_frac)
+{
+ struct uart_8250_port *up = up_to_u8250p(port);
+ u8 cpr2 = quot_frac >> 16;
+ u8 cpr = quot_frac >> 8;
+ u8 tcr = quot_frac;
+
+ serial_icr_write(up, UART_TCR, tcr);
+ serial_icr_write(up, UART_CPR, cpr);
+ serial_icr_write(up, UART_CKS, cpr2);
+ serial8250_do_set_divisor(port, baud, quot, 0);
+}
+
+/*
+ * For Tornado devices we force MCR[7] set for the Divide-by-M N/8 baud rate
+ * generator prescaler (CPR and CPR2). Otherwise no prescaler would be used.
+ */
+static void pci_oxsemi_tornado_set_mctrl(struct uart_port *port,
+ unsigned int mctrl)
+{
+ struct uart_8250_port *up = up_to_u8250p(port);
+
+ up->mcr |= UART_MCR_CLKSEL;
+ serial8250_do_set_mctrl(port, mctrl);
+}
+
+static int pci_oxsemi_tornado_setup(struct serial_private *priv,
+ const struct pciserial_board *board,
+ struct uart_8250_port *up, int idx)
+{
+ struct pci_dev *dev = priv->dev;
+
+ if (pci_oxsemi_tornado_p(dev)) {
+ up->port.get_divisor = pci_oxsemi_tornado_get_divisor;
+ up->port.set_divisor = pci_oxsemi_tornado_set_divisor;
+ up->port.set_mctrl = pci_oxsemi_tornado_set_mctrl;
+ }
+
+ return pci_default_setup(priv, board, up, idx);
+}
+