smiapp-pll.c

/*
 * drivers/media/i2c/smiapp-pll.c
 *
 * Generic driver for SMIA/SMIA++ compliant camera modules
 *
 * Copyright (C) 2011--2012 Nokia Corporation
 * Contact: Sakari Ailus <sakari.ailus@iki.fi>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 *
 */

#include <linux/gcd.h>
#include <linux/lcm.h>
#include <linux/module.h>

#include "smiapp-pll.h"

/* Return an even number or one. */
static inline uint32_t clk_div_even(uint32_t a)
{
	return max_t(uint32_t, 1, a & ~1);
}

/* Return an even number or one. */
static inline uint32_t clk_div_even_up(uint32_t a)
{
	if (a == 1)
		return 1;
	return (a + 1) & ~1;
}

static inline uint32_t is_one_or_even(uint32_t a)
{
	if (a == 1)
		return 1;
	if (a & 1)
		return 0;

	return 1;
}

static int bounds_check(struct device *dev, uint32_t val,
			uint32_t min, uint32_t max, char *str)
{
	if (val >= min && val <= max)
		return 0;

	dev_dbg(dev, "%s out of bounds: %d (%d--%d)\n", str, val, min, max);

	return -EINVAL;
}

static void print_pll(struct device *dev, struct smiapp_pll *pll)
{
	dev_dbg(dev, "pre_pll_clk_div\t%d\n",  pll->pre_pll_clk_div);
	dev_dbg(dev, "pll_multiplier \t%d\n",  pll->pll_multiplier);
	if (pll->flags != SMIAPP_PLL_FLAG_NO_OP_CLOCKS) {
		dev_dbg(dev, "op_sys_clk_div \t%d\n", pll->op_sys_clk_div);
		dev_dbg(dev, "op_pix_clk_div \t%d\n", pll->op_pix_clk_div);
	}
	dev_dbg(dev, "vt_sys_clk_div \t%d\n",  pll->vt_sys_clk_div);
	dev_dbg(dev, "vt_pix_clk_div \t%d\n",  pll->vt_pix_clk_div);

	dev_dbg(dev, "ext_clk_freq_hz \t%d\n", pll->ext_clk_freq_hz);
	dev_dbg(dev, "pll_ip_clk_freq_hz \t%d\n", pll->pll_ip_clk_freq_hz);
	dev_dbg(dev, "pll_op_clk_freq_hz \t%d\n", pll->pll_op_clk_freq_hz);
	if (pll->flags & SMIAPP_PLL_FLAG_NO_OP_CLOCKS) {
		dev_dbg(dev, "op_sys_clk_freq_hz \t%d\n",
			pll->op_sys_clk_freq_hz);
		dev_dbg(dev, "op_pix_clk_freq_hz \t%d\n",
			pll->op_pix_clk_freq_hz);
	}
	dev_dbg(dev, "vt_sys_clk_freq_hz \t%d\n", pll->vt_sys_clk_freq_hz);
	dev_dbg(dev, "vt_pix_clk_freq_hz \t%d\n", pll->vt_pix_clk_freq_hz);
}

/*
 * Heuristically guess the PLL tree for a given common multiplier and
 * divisor. Begin with the operational timing and continue to video
 * timing once operational timing has been verified.
 *
 * @mul is the PLL multiplier and @div is the common divisor
 * (pre_pll_clk_div and op_sys_clk_div combined). The final PLL
 * multiplier will be a multiple of @mul.
 *
 * @return Zero on success, error code on error.
 */
static int __smiapp_pll_calculate(struct device *dev,
				  const struct smiapp_pll_limits *limits,
				  struct smiapp_pll *pll, uint32_t mul,
				  uint32_t div, uint32_t lane_op_clock_ratio)
{
	uint32_t sys_div;
	uint32_t best_pix_div = INT_MAX >> 1;
	uint32_t vt_op_binning_div;
	/*
	 * Higher multipliers (and divisors) are often required than
	 * necessitated by the external clock and the output clocks.
	 * There are limits for all values in the clock tree. These
	 * are the minimum and maximum multiplier for mul.
	 */
	uint32_t more_mul_min, more_mul_max;
	uint32_t more_mul_factor;
	uint32_t min_vt_div, max_vt_div, vt_div;
	uint32_t min_sys_div, max_sys_div;
	unsigned int i;
	int rval;

	/*
	 * Get pre_pll_clk_div so that our pll_op_clk_freq_hz won't be
	 * too high.
	 */
	dev_dbg(dev, "pre_pll_clk_div %d\n", pll->pre_pll_clk_div);

	/* Don't go above max pll multiplier. */
	more_mul_max = limits->max_pll_multiplier / mul;
	dev_dbg(dev, "more_mul_max: max_pll_multiplier check: %d\n",
		more_mul_max);
	/* Don't go above max pll op frequency. */
	more_mul_max =
		min_t(uint32_t,
		      more_mul_max,
		      limits->max_pll_op_freq_hz
		      / (pll->ext_clk_freq_hz / pll->pre_pll_clk_div * mul));
	dev_dbg(dev, "more_mul_max: max_pll_op_freq_hz check: %d\n",
		more_mul_max);
	/* Don't go above the division capability of op sys clock divider. */
	more_mul_max = min(more_mul_max,
			   limits->op.max_sys_clk_div * pll->pre_pll_clk_div
			   / div);
	dev_dbg(dev, "more_mul_max: max_op_sys_clk_div check: %d\n",
		more_mul_max);
	/* Ensure we won't go above min_pll_multiplier. */
	more_mul_max = min(more_mul_max,
			   DIV_ROUND_UP(limits->max_pll_multiplier, mul));
	dev_dbg(dev, "more_mul_max: min_pll_multiplier check: %d\n",
		more_mul_max);

	/* Ensure we won't go below min_pll_op_freq_hz. */
	more_mul_min = DIV_ROUND_UP(limits->min_pll_op_freq_hz,
				    pll->ext_clk_freq_hz / pll->pre_pll_clk_div
				    * mul);
	dev_dbg(dev, "more_mul_min: min_pll_op_freq_hz check: %d\n",
		more_mul_min);
	/* Ensure we won't go below min_pll_multiplier. */
	more_mul_min = max(more_mul_min,
			   DIV_ROUND_UP(limits->min_pll_multiplier, mul));
	dev_dbg(dev, "more_mul_min: min_pll_multiplier check: %d\n",
		more_mul_min);

	if (more_mul_min > more_mul_max) {
		dev_dbg(dev,
			"unable to compute more_mul_min and more_mul_max\n");
		return -EINVAL;
	}

	more_mul_factor = lcm(div, pll->pre_pll_clk_div) / div;
	dev_dbg(dev, "more_mul_factor: %d\n", more_mul_factor);
	more_mul_factor = lcm(more_mul_factor, limits->op.min_sys_clk_div);
	dev_dbg(dev, "more_mul_factor: min_op_sys_clk_div: %d\n",
		more_mul_factor);
	i = roundup(more_mul_min, more_mul_factor);
	if (!is_one_or_even(i))
		i <<= 1;

	dev_dbg(dev, "final more_mul: %d\n", i);
	if (i > more_mul_max) {
		dev_dbg(dev, "final more_mul is bad, max %d\n", more_mul_max);
		return -EINVAL;
	}

	pll->pll_multiplier = mul * i;
	pll->op_sys_clk_div = div * i / pll->pre_pll_clk_div;
	dev_dbg(dev, "op_sys_clk_div: %d\n", pll->op_sys_clk_div);

	pll->pll_ip_clk_freq_hz = pll->ext_clk_freq_hz
		/ pll->pre_pll_clk_div;

	pll->pll_op_clk_freq_hz = pll->pll_ip_clk_freq_hz
		* pll->pll_multiplier;

	/* Derive pll_op_clk_freq_hz. */
	pll->op_sys_clk_freq_hz =
		pll->pll_op_clk_freq_hz / pll->op_sys_clk_div;

	pll->op_pix_clk_div = pll->bits_per_pixel;
	dev_dbg(dev, "op_pix_clk_div: %d\n", pll->op_pix_clk_div);

	pll->op_pix_clk_freq_hz =
		pll->op_sys_clk_freq_hz / pll->op_pix_clk_div;

	/*
	 * Some sensors perform analogue binning and some do this
	 * digitally. The ones doing this digitally can be roughly be
	 * found out using this formula. The ones doing this digitally
	 * should run at higher clock rate, so smaller divisor is used
	 * on video timing side.
	 */
	if (limits->min_line_length_pck_bin > limits->min_line_length_pck
	    / pll->binning_horizontal)
		vt_op_binning_div = pll->binning_horizontal;
	else
		vt_op_binning_div = 1;
	dev_dbg(dev, "vt_op_binning_div: %d\n", vt_op_binning_div);

	/*
	 * Profile 2 supports vt_pix_clk_div E [4, 10]
	 *
	 * Horizontal binning can be used as a base for difference in
	 * divisors. One must make sure that horizontal blanking is
	 * enough to accommodate the CSI-2 sync codes.
	 *
	 * Take scaling factor into account as well.
	 *
	 * Find absolute limits for the factor of vt divider.
	 */
	dev_dbg(dev, "scale_m: %d\n", pll->scale_m);
	min_vt_div = DIV_ROUND_UP(pll->op_pix_clk_div * pll->op_sys_clk_div
				  * pll->scale_n,
				  lane_op_clock_ratio * vt_op_binning_div
				  * pll->scale_m);

	/* Find smallest and biggest allowed vt divisor. */
	dev_dbg(dev, "min_vt_div: %d\n", min_vt_div);
	min_vt_div = max(min_vt_div,
			 DIV_ROUND_UP(pll->pll_op_clk_freq_hz,
				      limits->vt.max_pix_clk_freq_hz));
	dev_dbg(dev, "min_vt_div: max_vt_pix_clk_freq_hz: %d\n",
		min_vt_div);
	min_vt_div = max_t(uint32_t, min_vt_div,
			   limits->vt.min_pix_clk_div
			   * limits->vt.min_sys_clk_div);
	dev_dbg(dev, "min_vt_div: min_vt_clk_div: %d\n", min_vt_div);

	max_vt_div = limits->vt.max_sys_clk_div * limits->vt.max_pix_clk_div;
	dev_dbg(dev, "max_vt_div: %d\n", max_vt_div);
	max_vt_div = min(max_vt_div,
			 DIV_ROUND_UP(pll->pll_op_clk_freq_hz,
				      limits->vt.min_pix_clk_freq_hz));
	dev_dbg(dev, "max_vt_div: min_vt_pix_clk_freq_hz: %d\n",
		max_vt_div);

	/*
	 * Find limitsits for sys_clk_div. Not all values are possible
	 * with all values of pix_clk_div.
	 */
	min_sys_div = limits->vt.min_sys_clk_div;
	dev_dbg(dev, "min_sys_div: %d\n", min_sys_div);
	min_sys_div = max(min_sys_div,
			  DIV_ROUND_UP(min_vt_div,
				       limits->vt.max_pix_clk_div));
	dev_dbg(dev, "min_sys_div: max_vt_pix_clk_div: %d\n", min_sys_div);
	min_sys_div = max(min_sys_div,
			  pll->pll_op_clk_freq_hz
			  / limits->vt.max_sys_clk_freq_hz);
	dev_dbg(dev, "min_sys_div: max_pll_op_clk_freq_hz: %d\n", min_sys_div);
	min_sys_div = clk_div_even_up(min_sys_div);
	dev_dbg(dev, "min_sys_div: one or even: %d\n", min_sys_div);

	max_sys_div = limits->vt.max_sys_clk_div;
	dev_dbg(dev, "max_sys_div: %d\n", max_sys_div);
	max_sys_div = min(max_sys_div,
			  DIV_ROUND_UP(max_vt_div,
				       limits->vt.min_pix_clk_div));
	dev_dbg(dev, "max_sys_div: min_vt_pix_clk_div: %d\n", max_sys_div);
	max_sys_div = min(max_sys_div,
			  DIV_ROUND_UP(pll->pll_op_clk_freq_hz,
				       limits->vt.min_pix_clk_freq_hz));
	dev_dbg(dev, "max_sys_div: min_vt_pix_clk_freq_hz: %d\n", max_sys_div);

	/*
	 * Find pix_div such that a legal pix_div * sys_div results
	 * into a value which is not smaller than div, the desired
	 * divisor.
	 */
	for (vt_div = min_vt_div; vt_div <= max_vt_div;
	     vt_div += 2 - (vt_div & 1)) {
		for (sys_div = min_sys_div;
		     sys_div <= max_sys_div;
		     sys_div += 2 - (sys_div & 1)) {
			uint16_t pix_div = DIV_ROUND_UP(vt_div, sys_div);

			if (pix_div < limits->vt.min_pix_clk_div
			    || pix_div > limits->vt.max_pix_clk_div) {
				dev_dbg(dev,
					"pix_div %d too small or too big (%d--%d)\n",
					pix_div,
					limits->vt.min_pix_clk_div,
					limits->vt.max_pix_clk_div);
				continue;
			}

			/* Check if this one is better. */
			if (pix_div * sys_div
			    <= roundup(min_vt_div, best_pix_div))
				best_pix_div = pix_div;
		}
		if (best_pix_div < INT_MAX >> 1)
			break;
	}

	pll->vt_sys_clk_div = DIV_ROUND_UP(min_vt_div, best_pix_div);
	pll->vt_pix_clk_div = best_pix_div;

	pll->vt_sys_clk_freq_hz =
		pll->pll_op_clk_freq_hz / pll->vt_sys_clk_div;
	pll->vt_pix_clk_freq_hz =
		pll->vt_sys_clk_freq_hz / pll->vt_pix_clk_div;

	pll->pixel_rate_csi =
		pll->op_pix_clk_freq_hz * lane_op_clock_ratio;

	rval = bounds_check(dev, pll->pll_ip_clk_freq_hz,
			    limits->min_pll_ip_freq_hz,
			    limits->max_pll_ip_freq_hz,
			    "pll_ip_clk_freq_hz");
	if (!rval)
		rval = bounds_check(
			dev, pll->pll_multiplier,
			limits->min_pll_multiplier, limits->max_pll_multiplier,
			"pll_multiplier");
	if (!rval)
		rval = bounds_check(
			dev, pll->pll_op_clk_freq_hz,
			limits->min_pll_op_freq_hz, limits->max_pll_op_freq_hz,
			"pll_op_clk_freq_hz");
	if (!rval)
		rval = bounds_check(
			dev, pll->op_sys_clk_div,
			limits->op.min_sys_clk_div, limits->op.max_sys_clk_div,
			"op_sys_clk_div");
	if (!rval)
		rval = bounds_check(
			dev, pll->op_pix_clk_div,
			limits->op.min_pix_clk_div, limits->op.max_pix_clk_div,
			"op_pix_clk_div");
	if (!rval)
		rval = bounds_check(
			dev, pll->op_sys_clk_freq_hz,
			limits->op.min_sys_clk_freq_hz,
			limits->op.max_sys_clk_freq_hz,
			"op_sys_clk_freq_hz");
	if (!rval)
		rval = bounds_check(
			dev, pll->op_pix_clk_freq_hz,
			limits->op.min_pix_clk_freq_hz,
			limits->op.max_pix_clk_freq_hz,
			"op_pix_clk_freq_hz");
	if (!rval)
		rval = bounds_check(
			dev, pll->vt_sys_clk_freq_hz,
			limits->vt.min_sys_clk_freq_hz,
			limits->vt.max_sys_clk_freq_hz,
			"vt_sys_clk_freq_hz");
	if (!rval)
		rval = bounds_check(
			dev, pll->vt_pix_clk_freq_hz,
			limits->vt.min_pix_clk_freq_hz,
			limits->vt.max_pix_clk_freq_hz,
			"vt_pix_clk_freq_hz");

	return rval;
}

int smiapp_pll_calculate(struct device *dev,
			 const struct smiapp_pll_limits *limits,
			 struct smiapp_pll *pll)
{
	uint16_t min_pre_pll_clk_div;
	uint16_t max_pre_pll_clk_div;
	uint32_t lane_op_clock_ratio;
	uint32_t mul, div;
	unsigned int i;
	int rval = -EINVAL;

	if (pll->flags & SMIAPP_PLL_FLAG_OP_PIX_CLOCK_PER_LANE)
		lane_op_clock_ratio = pll->csi2.lanes;
	else
		lane_op_clock_ratio = 1;
	dev_dbg(dev, "lane_op_clock_ratio: %d\n", lane_op_clock_ratio);

	dev_dbg(dev, "binning: %dx%d\n", pll->binning_horizontal,
		pll->binning_vertical);

	switch (pll->bus_type) {
	case SMIAPP_PLL_BUS_TYPE_CSI2:
		/* CSI transfers 2 bits per clock per lane; thus times 2 */
		pll->pll_op_clk_freq_hz = pll->link_freq * 2
			* (pll->csi2.lanes / lane_op_clock_ratio);
		break;
	case SMIAPP_PLL_BUS_TYPE_PARALLEL:
		pll->pll_op_clk_freq_hz = pll->link_freq * pll->bits_per_pixel
			/ DIV_ROUND_UP(pll->bits_per_pixel,
				       pll->parallel.bus_width);
		break;
	default:
		return -EINVAL;
	}

	/* Figure out limits for pre-pll divider based on extclk */
	dev_dbg(dev, "min / max pre_pll_clk_div: %d / %d\n",
		limits->min_pre_pll_clk_div, limits->max_pre_pll_clk_div);
	max_pre_pll_clk_div =
		min_t(uint16_t, limits->max_pre_pll_clk_div,
		      clk_div_even(pll->ext_clk_freq_hz /
				   limits->min_pll_ip_freq_hz));
	min_pre_pll_clk_div =
		max_t(uint16_t, limits->min_pre_pll_clk_div,
		      clk_div_even_up(
			      DIV_ROUND_UP(pll->ext_clk_freq_hz,
					   limits->max_pll_ip_freq_hz)));
	dev_dbg(dev, "pre-pll check: min / max pre_pll_clk_div: %d / %d\n",
		min_pre_pll_clk_div, max_pre_pll_clk_div);

	i = gcd(pll->pll_op_clk_freq_hz, pll->ext_clk_freq_hz);
	mul = div_u64(pll->pll_op_clk_freq_hz, i);
	div = pll->ext_clk_freq_hz / i;
	dev_dbg(dev, "mul %d / div %d\n", mul, div);

	min_pre_pll_clk_div =
		max_t(uint16_t, min_pre_pll_clk_div,
		      clk_div_even_up(
			      DIV_ROUND_UP(mul * pll->ext_clk_freq_hz,
					   limits->max_pll_op_freq_hz)));
	dev_dbg(dev, "pll_op check: min / max pre_pll_clk_div: %d / %d\n",
		min_pre_pll_clk_div, max_pre_pll_clk_div);

	for (pll->pre_pll_clk_div = min_pre_pll_clk_div;
	     pll->pre_pll_clk_div <= max_pre_pll_clk_div;
	     pll->pre_pll_clk_div += 2 - (pll->pre_pll_clk_div & 1)) {
		rval = __smiapp_pll_calculate(dev, limits, pll, mul, div,
					      lane_op_clock_ratio);
		if (rval)
			continue;

		print_pll(dev, pll);
		return 0;
	}

	dev_info(dev, "unable to compute pre_pll divisor\n");
	return rval;
}
EXPORT_SYMBOL_GPL(smiapp_pll_calculate);

MODULE_AUTHOR("Sakari Ailus <sakari.ailus@iki.fi>");
MODULE_DESCRIPTION("Generic SMIA/SMIA++ PLL calculator");
MODULE_LICENSE("GPL");