mgag200_bmc.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2
 3#include <linux/delay.h>
 4#include <linux/iopoll.h>
 5
 6#include <drm/drm_atomic_helper.h>
 7#include <drm/drm_edid.h>
 8#include <drm/drm_managed.h>
 9#include <drm/drm_probe_helper.h>
10
11#include "mgag200_drv.h"
12
13void mgag200_bmc_stop_scanout(struct mga_device *mdev)
14{
15	u8 tmp;
16	int ret;
17
18	/*
19	 * 1 - The first step is to inform the BMC of an upcoming mode
20	 * change. We are putting the misc<0> to output.
21	 */
22
23	WREG8(DAC_INDEX, MGA1064_GEN_IO_CTL);
24	tmp = RREG8(DAC_DATA);
25	tmp |= 0x10;
26	WREG_DAC(MGA1064_GEN_IO_CTL, tmp);
27
28	/* we are putting a 1 on the misc<0> line */
29	WREG8(DAC_INDEX, MGA1064_GEN_IO_DATA);
30	tmp = RREG8(DAC_DATA);
31	tmp |= 0x10;
32	WREG_DAC(MGA1064_GEN_IO_DATA, tmp);
33
34	/*
35	 * 2- Second step to mask any further scan request. This is
36	 * done by asserting the remfreqmsk bit (XSPAREREG<7>)
37	 */
38
39	WREG8(DAC_INDEX, MGA1064_SPAREREG);
40	tmp = RREG8(DAC_DATA);
41	tmp |= 0x80;
42	WREG_DAC(MGA1064_SPAREREG, tmp);
43
44	/*
45	 * 3a- The third step is to verify if there is an active scan.
46	 * We are waiting for a 0 on remhsyncsts (<XSPAREREG<0>).
47	 */
48	ret = read_poll_timeout(RREG_DAC, tmp, !(tmp & 0x1),
49				1000, 300000, false,
50				MGA1064_SPAREREG);
51	if (ret == -ETIMEDOUT)
52		return;
53
54	/*
55	 * 3b- This step occurs only if the remote BMC is actually
56	 * scanning. We are waiting for the end of the frame which is
57	 * a 1 on remvsyncsts (XSPAREREG<1>)
58	 */
59	(void)read_poll_timeout(RREG_DAC, tmp, (tmp & 0x2),
60				1000, 300000, false,
61				MGA1064_SPAREREG);
62}
63
64void mgag200_bmc_start_scanout(struct mga_device *mdev)
65{
66	u8 tmp;
67
68	/* Assert rstlvl2 */
69	WREG8(DAC_INDEX, MGA1064_REMHEADCTL2);
70	tmp = RREG8(DAC_DATA);
71	tmp |= 0x8;
72	WREG8(DAC_DATA, tmp);
73
74	udelay(10);
75
76	/* Deassert rstlvl2 */
77	tmp &= ~0x08;
78	WREG8(DAC_INDEX, MGA1064_REMHEADCTL2);
79	WREG8(DAC_DATA, tmp);
80
81	/* Remove mask of scan request */
82	WREG8(DAC_INDEX, MGA1064_SPAREREG);
83	tmp = RREG8(DAC_DATA);
84	tmp &= ~0x80;
85	WREG8(DAC_DATA, tmp);
86
87	/* Put back a 0 on the misc<0> line */
88	WREG8(DAC_INDEX, MGA1064_GEN_IO_DATA);
89	tmp = RREG8(DAC_DATA);
90	tmp &= ~0x10;
91	WREG_DAC(MGA1064_GEN_IO_DATA, tmp);
92}