1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2016 Noralf Trønnes
*/
#include <linux/backlight.h>
#include <linux/dma-buf.h>
#include <linux/module.h>
#include <linux/pm.h>
#include <linux/spi/spi.h>
#include <linux/swab.h>
#include <drm/drm_device.h>
#include <drm/drm_drv.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_print.h>
#include <drm/drm_rect.h>
#include <drm/tinydrm/tinydrm-helpers.h>
#if IS_ENABLED(CONFIG_SPI)
/**
* tinydrm_spi_transfer - SPI transfer helper
* @spi: SPI device
* @speed_hz: Override speed (optional)
* @header: Optional header transfer
* @bpw: Bits per word
* @buf: Buffer to transfer
* @len: Buffer length
*
* This SPI transfer helper breaks up the transfer of @buf into chunks which
* the SPI master driver can handle. If the machine is Little Endian and the
* SPI master driver doesn't support 16 bits per word, it swaps the bytes and
* does a 8-bit transfer.
* If @header is set, it is prepended to each SPI message.
*
* Returns:
* Zero on success, negative error code on failure.
*/
int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,
struct spi_transfer *header, u8 bpw, const void *buf,
size_t len)
{
size_t max_chunk = spi_max_transfer_size(spi);
struct spi_transfer tr = {
.bits_per_word = bpw,
.speed_hz = speed_hz,
};
struct spi_message m;
u16 *swap_buf = NULL;
size_t chunk;
int ret = 0;
if (WARN_ON_ONCE(bpw != 8 && bpw != 16))
return -EINVAL;
if (bpw == 16 && !spi_is_bpw_supported(spi, 16)) {
tr.bits_per_word = 8;
if (tinydrm_machine_little_endian()) {
swap_buf = kmalloc(min(len, max_chunk), GFP_KERNEL);
if (!swap_buf)
return -ENOMEM;
}
}
spi_message_init(&m);
if (header)
spi_message_add_tail(header, &m);
spi_message_add_tail(&tr, &m);
while (len) {
chunk = min(len, max_chunk);
tr.tx_buf = buf;
tr.len = chunk;
if (swap_buf) {
const u16 *buf16 = buf;
unsigned int i;
for (i = 0; i < chunk / 2; i++)
swap_buf[i] = swab16(buf16[i]);
tr.tx_buf = swap_buf;
}
buf += chunk;
len -= chunk;
ret = spi_sync(spi, &m);
if (ret)
return ret;
}
return 0;
}
EXPORT_SYMBOL(tinydrm_spi_transfer);
#endif /* CONFIG_SPI */
MODULE_LICENSE("GPL");
|
