1// SPDX-License-Identifier: GPL-2.0
2//
3// mcp251xfd - Microchip MCP251xFD Family CAN controller driver
4//
5// Copyright (c) 2021, 2022 Pengutronix,
6// Marc Kleine-Budde <kernel@pengutronix.de>
7//
8
9#include "mcp251xfd-ram.h"
10
11static inline u8 can_ram_clamp(const struct can_ram_config *config,
12 const struct can_ram_obj_config *obj,
13 u8 val)
14{
15 u8 max;
16
17 max = min_t(u8, obj->max, obj->fifo_num * config->fifo_depth);
18 return clamp(val, obj->min, max);
19}
20
21static u8
22can_ram_rounddown_pow_of_two(const struct can_ram_config *config,
23 const struct can_ram_obj_config *obj,
24 const u8 coalesce, u8 val)
25{
26 u8 fifo_num = obj->fifo_num;
27 u8 ret = 0, i;
28
29 val = can_ram_clamp(config, obj, val);
30
31 if (coalesce) {
32 /* Use 1st FIFO for coalescing, if requested.
33 *
34 * Either use complete FIFO (and FIFO Full IRQ) for
35 * coalescing or only half of FIFO (FIFO Half Full
36 * IRQ) and use remaining half for normal objects.
37 */
38 ret = min_t(u8, coalesce * 2, config->fifo_depth);
39 val -= ret;
40 fifo_num--;
41 }
42
43 for (i = 0; i < fifo_num && val; i++) {
44 u8 n;
45
46 n = min_t(u8, rounddown_pow_of_two(val),
47 config->fifo_depth);
48
49 /* skip small FIFOs */
50 if (n < obj->fifo_depth_min)
51 return ret;
52
53 ret += n;
54 val -= n;
55 }
56
57 return ret;
58}
59
60void can_ram_get_layout(struct can_ram_layout *layout,
61 const struct can_ram_config *config,
62 const struct ethtool_ringparam *ring,
63 const struct ethtool_coalesce *ec,
64 const bool fd_mode)
65{
66 u8 num_rx, num_tx;
67 u16 ram_free;
68
69 /* default CAN */
70
71 num_tx = config->tx.def[fd_mode];
72 num_tx = can_ram_rounddown_pow_of_two(config, obj: &config->tx, coalesce: 0, val: num_tx);
73
74 ram_free = config->size;
75 ram_free -= config->tx.size[fd_mode] * num_tx;
76
77 num_rx = ram_free / config->rx.size[fd_mode];
78
79 layout->default_rx = can_ram_rounddown_pow_of_two(config, obj: &config->rx, coalesce: 0, val: num_rx);
80 layout->default_tx = num_tx;
81
82 /* MAX CAN */
83
84 ram_free = config->size;
85 ram_free -= config->tx.size[fd_mode] * config->tx.min;
86 num_rx = ram_free / config->rx.size[fd_mode];
87
88 ram_free = config->size;
89 ram_free -= config->rx.size[fd_mode] * config->rx.min;
90 num_tx = ram_free / config->tx.size[fd_mode];
91
92 layout->max_rx = can_ram_rounddown_pow_of_two(config, obj: &config->rx, coalesce: 0, val: num_rx);
93 layout->max_tx = can_ram_rounddown_pow_of_two(config, obj: &config->tx, coalesce: 0, val: num_tx);
94
95 /* cur CAN */
96
97 if (ring) {
98 u8 num_rx_coalesce = 0, num_tx_coalesce = 0;
99
100 num_rx = can_ram_rounddown_pow_of_two(config, obj: &config->rx, coalesce: 0, val: ring->rx_pending);
101
102 /* The ethtool doc says:
103 * To disable coalescing, set usecs = 0 and max_frames = 1.
104 */
105 if (ec && !(ec->rx_coalesce_usecs_irq == 0 &&
106 ec->rx_max_coalesced_frames_irq == 1)) {
107 u8 max;
108
109 /* use only max half of available objects for coalescing */
110 max = min_t(u8, num_rx / 2, config->fifo_depth);
111 num_rx_coalesce = clamp(ec->rx_max_coalesced_frames_irq,
112 (u32)config->rx.fifo_depth_coalesce_min,
113 (u32)max);
114 num_rx_coalesce = rounddown_pow_of_two(num_rx_coalesce);
115
116 num_rx = can_ram_rounddown_pow_of_two(config, obj: &config->rx,
117 coalesce: num_rx_coalesce, val: num_rx);
118 }
119
120 ram_free = config->size - config->rx.size[fd_mode] * num_rx;
121 num_tx = ram_free / config->tx.size[fd_mode];
122 num_tx = min_t(u8, ring->tx_pending, num_tx);
123 num_tx = can_ram_rounddown_pow_of_two(config, obj: &config->tx, coalesce: 0, val: num_tx);
124
125 /* The ethtool doc says:
126 * To disable coalescing, set usecs = 0 and max_frames = 1.
127 */
128 if (ec && !(ec->tx_coalesce_usecs_irq == 0 &&
129 ec->tx_max_coalesced_frames_irq == 1)) {
130 u8 max;
131
132 /* use only max half of available objects for coalescing */
133 max = min_t(u8, num_tx / 2, config->fifo_depth);
134 num_tx_coalesce = clamp(ec->tx_max_coalesced_frames_irq,
135 (u32)config->tx.fifo_depth_coalesce_min,
136 (u32)max);
137 num_tx_coalesce = rounddown_pow_of_two(num_tx_coalesce);
138
139 num_tx = can_ram_rounddown_pow_of_two(config, obj: &config->tx,
140 coalesce: num_tx_coalesce, val: num_tx);
141 }
142
143 layout->cur_rx = num_rx;
144 layout->cur_tx = num_tx;
145 layout->rx_coalesce = num_rx_coalesce;
146 layout->tx_coalesce = num_tx_coalesce;
147 } else {
148 layout->cur_rx = layout->default_rx;
149 layout->cur_tx = layout->default_tx;
150 layout->rx_coalesce = 0;
151 layout->tx_coalesce = 0;
152 }
153}
154

source code of linux/drivers/net/can/spi/mcp251xfd/mcp251xfd-ram.c