drivers/gpu/drm/mgag200/mgag200_bmc.c

// SPDX-License-Identifier: GPL-2.0-only

#include <linux/delay.h>

#include <drm/drm_atomic_helper.h>
#include <drm/drm_edid.h>
#include <drm/drm_managed.h>
#include <drm/drm_probe_helper.h>

#include "mgag200_drv.h"

void mgag200_bmc_stop_scanout(struct mga_device *mdev)
{
	u8 tmp;
	int iter_max;

	/*
	 * 1 - The first step is to inform the BMC of an upcoming mode
	 * change. We are putting the misc<0> to output.
	 */

	WREG8(DAC_INDEX, MGA1064_GEN_IO_CTL);
	tmp = RREG8(DAC_DATA);
	tmp |= 0x10;
	WREG_DAC(MGA1064_GEN_IO_CTL, tmp);

	/* we are putting a 1 on the misc<0> line */
	WREG8(DAC_INDEX, MGA1064_GEN_IO_DATA);
	tmp = RREG8(DAC_DATA);
	tmp |= 0x10;
	WREG_DAC(MGA1064_GEN_IO_DATA, tmp);

	/*
	 * 2- Second step to mask any further scan request. This is
	 * done by asserting the remfreqmsk bit (XSPAREREG<7>)
	 */

	WREG8(DAC_INDEX, MGA1064_SPAREREG);
	tmp = RREG8(DAC_DATA);
	tmp |= 0x80;
	WREG_DAC(MGA1064_SPAREREG, tmp);

	/*
	 * 3a- The third step is to verify if there is an active scan.
	 * We are waiting for a 0 on remhsyncsts <XSPAREREG<0>).
	 */
	iter_max = 300;
	while (!(tmp & 0x1) && iter_max) {
		WREG8(DAC_INDEX, MGA1064_SPAREREG);
		tmp = RREG8(DAC_DATA);
		udelay(1000);
		iter_max--;
	}

	/*
	 * 3b- This step occurs only if the remove is actually
	 * scanning. We are waiting for the end of the frame which is
	 * a 1 on remvsyncsts (XSPAREREG<1>)
	 */
	if (iter_max) {
		iter_max = 300;
		while ((tmp & 0x2) && iter_max) {
			WREG8(DAC_INDEX, MGA1064_SPAREREG);
			tmp = RREG8(DAC_DATA);
			udelay(1000);
			iter_max--;
		}
	}
}

void mgag200_bmc_start_scanout(struct mga_device *mdev)
{
	u8 tmp;

	/* Assert rstlvl2 */
	WREG8(DAC_INDEX, MGA1064_REMHEADCTL2);
	tmp = RREG8(DAC_DATA);
	tmp |= 0x8;
	WREG8(DAC_DATA, tmp);

	udelay(10);

	/* Deassert rstlvl2 */
	tmp &= ~0x08;
	WREG8(DAC_INDEX, MGA1064_REMHEADCTL2);
	WREG8(DAC_DATA, tmp);

	/* Remove mask of scan request */
	WREG8(DAC_INDEX, MGA1064_SPAREREG);
	tmp = RREG8(DAC_DATA);
	tmp &= ~0x80;
	WREG8(DAC_DATA, tmp);

	/* Put back a 0 on the misc<0> line */
	WREG8(DAC_INDEX, MGA1064_GEN_IO_DATA);
	tmp = RREG8(DAC_DATA);
	tmp &= ~0x10;
	WREG_DAC(MGA1064_GEN_IO_DATA, tmp);
}