path: root/drivers/gpu/drm/drm_dp_helper.c

/*
 * Copyright © 2009 Keith Packard
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/seq_file.h>

#include <drm/drm_dp_helper.h>
#include <drm/drm_print.h>
#include <drm/drm_vblank.h>
#include <drm/drm_dp_mst_helper.h>

#include "drm_crtc_helper_internal.h"

/**
 * DOC: dp helpers
 *
 * These functions contain some common logic and helpers at various abstraction
 * levels to deal with Display Port sink devices and related things like DP aux
 * channel transfers, EDID reading over DP aux channels, decoding certain DPCD
 * blocks, ...
 */

/* Helpers for DP link training */
static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r)
{
	return link_status[r - DP_LANE0_1_STATUS];
}

static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE],
			     int lane)
{
	int i = DP_LANE0_1_STATUS + (lane >> 1);
	int s = (lane & 1) * 4;
	u8 l = dp_link_status(link_status, i);
	return (l >> s) & 0xf;
}

bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
			  int lane_count)
{
	u8 lane_align;
	u8 lane_status;
	int lane;

	lane_align = dp_link_status(link_status,
				    DP_LANE_ALIGN_STATUS_UPDATED);
	if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0)
		return false;
	for (lane = 0; lane < lane_count; lane++) {
		lane_status = dp_get_lane_status(link_status, lane);
		if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS)
			return false;
	}
	return true;
}
EXPORT_SYMBOL(drm_dp_channel_eq_ok);

bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
			      int lane_count)
{
	int lane;
	u8 lane_status;

	for (lane = 0; lane < lane_count; lane++) {
		lane_status = dp_get_lane_status(link_status, lane);
		if ((lane_status & DP_LANE_CR_DONE) == 0)
			return false;
	}
	return true;
}
EXPORT_SYMBOL(drm_dp_clock_recovery_ok);

u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
				     int lane)
{
	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
	int s = ((lane & 1) ?
		 DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT :
		 DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT);
	u8 l = dp_link_status(link_status, i);

	return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage);

u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
					  int lane)
{
	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
	int s = ((lane & 1) ?
		 DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT :
		 DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT);
	u8 l = dp_link_status(link_status, i);

	return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);

u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE],
					 unsigned int lane)
{
	unsigned int offset = DP_ADJUST_REQUEST_POST_CURSOR2;
	u8 value = dp_link_status(link_status, offset);

	return (value >> (lane << 1)) & 0x3;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_post_cursor);

void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
	unsigned long rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
					 DP_TRAINING_AUX_RD_MASK;

	if (rd_interval > 4)
		DRM_DEBUG_KMS("AUX interval %lu, out of range (max 4)\n",
			      rd_interval);

	if (rd_interval == 0 || dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
		rd_interval = 100;
	else
		rd_interval *= 4 * USEC_PER_MSEC;

	usleep_range(rd_interval, rd_interval * 2);
}
EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);

void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
	unsigned long rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
					 DP_TRAINING_AUX_RD_MASK;

	if (rd_interval > 4)
		DRM_DEBUG_KMS("AUX interval %lu, out of range (max 4)\n",
			      rd_interval);

	if (rd_interval == 0)
		rd_interval = 400;
	else
		rd_interval *= 4 * USEC_PER_MSEC;

	usleep_range(rd_interval, rd_interval * 2);
}
EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);

u8 drm_dp_link_rate_to_bw_code(int link_rate)
{
	/* Spec says link_bw = link_rate / 0.27Gbps */
	return link_rate / 27000;
}
EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);

int drm_dp_bw_code_to_link_rate(u8 link_bw)
{
	/* Spec says link_rate = link_bw * 0.27Gbps */
	return link_bw * 27000;
}
EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);

#define AUX_RETRY_INTERVAL 500 /* us */

static inline void
drm_dp_dump_access(const struct drm_dp_aux *aux,
		   u8 request, uint offset, void *buffer, int ret)
{
	const char *arrow = request == DP_AUX_NATIVE_READ ? "->" : "<-";

	if (ret > 0)
		DRM_DEBUG_DP("%s: 0x%05x AUX %s (ret=%3d) %*ph\n",
			     aux->name, offset, arrow, ret, min(ret, 20), buffer);
	else
		DRM_DEBUG_DP("%s: 0x%05x AUX %s (ret=%3d)\n",
			     aux->name, offset, arrow, ret);
}

/**
 * DOC: dp helpers
 *
 * The DisplayPort AUX channel is an abstraction to allow generic, driver-
 * independent access to AUX functionality. Drivers can take advantage of
 * this by filling in the fields of the drm_dp_aux structure.
 *
 * Transactions are described using a hardware-independent drm_dp_aux_msg
 * structure, which is passed into a driver's .transfer() implementation.
 * Both native and I2C-over-AUX transactions are supported.
 */

static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
			      unsigned int offset, void *buffer, size_t size)
{
	struct drm_dp_aux_msg msg;
	unsigned int retry, native_reply;
	int err = 0, ret = 0;

	memset(&msg, 0, sizeof(msg));
	msg.address = offset;
	msg.request = request;
	msg.buffer = buffer;
	msg.size = size;

	mutex_lock(&aux->hw_mutex);

	/*
	 * The specification doesn't give any recommendation on how often to
	 * retry native transactions. We used to retry 7 times like for
	 * aux i2c transactions but real world devices this wasn't
	 * sufficient, bump t