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/*

 *  linux/include/asm-arm/arch-rpc/acornfb.h

 *

 *  Copyright (C) 1999 Russell King

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 *  AcornFB architecture specific code

 */

#define acornfb_valid_pixrate(rate) (1)

/*

 * Try to find the best PLL parameters for the pixel clock.

 * This algorithm seems to give best predictable results,

 * and produces the same values as detailed in the VIDC20

 * data sheet.

 */

static inline u_int

acornfb_vidc20_find_pll(u_int pixclk)

{

        u_int r, best_r = 2, best_v = 2;

        int best_d = 0x7fffffff;

        for (r = 2; r <= 32; r++) {

                u_int rr, v, p;

                int d;

                rr = 41667 * r;

                v = (rr + pixclk / 2) / pixclk;

                if (v > 32 || v < 2)

                        continue;

                p = (rr + v / 2) / v;

                d = pixclk - p;

                if (d < 0)

                        d = -d;

                if (d < best_d) {

                        best_d = d;

                        best_v = v - 1;

                        best_r = r - 1;

                }

                if (d == 0)

                        break;

        }

        return best_v << 8 | best_r;

}

static inline void

acornfb_vidc20_find_rates(struct vidc_timing *vidc,

                          struct fb_var_screeninfo *var)

{

        u_int div, bandwidth;

        /* Select pixel-clock divisor to keep PLL in range */

        div = var->pixclock / 9090; /*9921*/

        /* Limit divisor */

        if (div == 0)

                div = 1;

        if (div > 8)

                div = 8;

        /* Encode divisor to VIDC20 setting */

        switch (div) {

        case 1: vidc->control |= VIDC20_CTRL_PIX_CK;  break;

        case 2: vidc->control |= VIDC20_CTRL_PIX_CK2; break;

        case 3: vidc->control |= VIDC20_CTRL_PIX_CK3; break;

        case 4: vidc->control |= VIDC20_CTRL_PIX_CK4; break;

        case 5: vidc->control |= VIDC20_CTRL_PIX_CK5; break;

        case 6: vidc->control |= VIDC20_CTRL_PIX_CK6; break;

        case 7: vidc->control |= VIDC20_CTRL_PIX_CK7; break;

        case 8: vidc->control |= VIDC20_CTRL_PIX_CK8; break;

        }

        /* Calculate bandwidth */

        bandwidth = var->pixclock * 8 / var->bits_per_pixel;

        /* Encode bandwidth as VIDC20 setting */

        if (bandwidth > 33334)

                vidc->control |= VIDC20_CTRL_FIFO_16;   /* < 30.0MB/s */

        else if (bandwidth > 26666)

                vidc->control |= VIDC20_CTRL_FIFO_20;   /* < 37.5MB/s */

        else if (bandwidth > 22222)

                vidc->control |= VIDC20_CTRL_FIFO_24;   /* < 45.0MB/s */

        else

                vidc->control |= VIDC20_CTRL_FIFO_28;   /* > 45.0MB/s */

        /* Find the PLL values */

        vidc->pll_ctl  = acornfb_vidc20_find_pll(var->pixclock / div);

}

#define acornfb_default_control()       (VIDC20_CTRL_PIX_VCLK)

#define acornfb_default_econtrol()      (VIDC20_ECTL_DAC | VIDC20_ECTL_REG(3))