mipi-phy.c

/*
 * Copyright (C) 2013 NVIDIA Corporation
 *
 * 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.
 */

#include <linux/errno.h>
#include <linux/kernel.h>

#include "mipi-phy.h"

/*
 * Default D-PHY timings based on MIPI D-PHY specification. Derived from the
 * valid ranges specified in Section 6.9, Table 14, Page 40 of the D-PHY
 * specification (v1.2) with minor adjustments.
 */
int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
				 unsigned long period)
{
	timing->clkmiss = 0;
	timing->clkpost = 70 + 52 * period;
	timing->clkpre = 8;
	timing->clkprepare = 65;
	timing->clksettle = 95;
	timing->clktermen = 0;
	timing->clktrail = 80;
	timing->clkzero = 260;
	timing->dtermen = 0;
	timing->eot = 0;
	timing->hsexit = 120;
	timing->hsprepare = 65 + 5 * period;
	timing->hszero = 145 + 5 * period;
	timing->hssettle = 85 + 6 * period;
	timing->hsskip = 40;

	/*
	 * The MIPI D-PHY specification (Section 6.9, v1.2, Table 14, Page 40)
	 * contains this formula as:
	 *
	 *     T_HS-TRAIL = max(n * 8 * period, 60 + n * 4 * period)
	 *
	 * where n = 1 for forward-direction HS mode and n = 4 for reverse-
	 * direction HS mode. There's only one setting and this function does
	 * not parameterize on anything other that period, so this code will
	 * assumes that reverse-direction HS mode is supported and uses n = 4.
	 */
	timing->hstrail = max(4 * 8 * period, 60 + 4 * 4 * period);

	timing->init = 100000;
	timing->lpx = 60;
	timing->taget = 5 * timing->lpx;
	timing->tago = 4 * timing->lpx;
	timing->tasure = 2 * timing->lpx;
	timing->wakeup = 1000000;

	return 0;
}

/*
 * Validate D-PHY timing according to MIPI D-PHY specification (v1.2, Section
 * Section 6.9 "Global Operation Timing Parameters").
 */
int mipi_dphy_timing_validate(struct mipi_dphy_timing *timing,
			      unsigned long period)
{
	if (timing->clkmiss > 60)
		return -EINVAL;

	if (timing->clkpost < (60 + 52 * period))
		return -EINVAL;

	if (timing->clkpre < 8)
		return -EINVAL;

	if (timing->clkprepare < 38 || timing->clkprepare > 95)
		return -EINVAL;

	if (timing->clksettle < 95 || timing->clksettle > 300)
		return -EINVAL;

	if (timing->clktermen > 38)
		return -EINVAL;

	if (timing->clktrail < 60)
		return -EINVAL;

	if (timing->clkprepare + timing->clkzero < 300)
		return -EINVAL;

	if (timing->dtermen > 35 + 4 * period)
		return -EINVAL;

	if (timing->eot > 105 + 12 * period)
		return -EINVAL;

	if (timing->hsexit < 100)
		return -EINVAL;

	if (timing->hsprepare < 40 + 4 * period ||
	    timing->hsprepare > 85 + 6 * period)
		return -EINVAL;

	if (timing->hsprepare + timing->hszero < 145 + 10 * period)
		return -EINVAL;

	if ((timing->hssettle < 85 + 6 * period) ||
	    (timing->hssettle > 145 + 10 * period))
		return -EINVAL;

	if (timing->hsskip < 40 || timing->hsskip > 55 + 4 * period)
		return -EINVAL;

	if (timing->hstrail < max(8 * period, 60 + 4 * period))
		return -EINVAL;

	if (timing->init < 100000)
		return -EINVAL;

	if (timing->lpx < 50)
		return -EINVAL;

	if (timing->taget != 5 * timing->lpx)
		return -EINVAL;

	if (timing->tago != 4 * timing->lpx)
		return -EINVAL;

	if (timing->tasure < timing->lpx || timing->tasure > 2 * timing->lpx)
		return -EINVAL;

	if (timing->wakeup < 1000000)
		return -EINVAL;

	return 0;
}