d84ad671259100472f3b6fd99a062f2e6d1362e4
[openwrt/staging/blocktrron.git] /
1 From a64c3c1357275b1fd61bc9734f638cdb5d8a8bbb Mon Sep 17 00:00:00 2001
2 From: =?UTF-8?q?Marek=20Beh=C3=BAn?= <kabel@kernel.org>
3 Date: Mon, 18 Sep 2023 18:11:02 +0200
4 Subject: [PATCH 4/6] leds: turris-omnia: Make set_brightness() more efficient
5 MIME-Version: 1.0
6 Content-Type: text/plain; charset=UTF-8
7 Content-Transfer-Encoding: 8bit
8
9 Implement caching of the LED color and state values that are sent to MCU
10 in order to make the set_brightness() operation more efficient by
11 avoiding I2C transactions which are not needed.
12
13 On Turris Omnia's MCU, which acts as the RGB LED controller, each LED
14 has a RGB color, and a ON/OFF state, which are configurable via I2C
15 commands CMD_LED_COLOR and CMD_LED_STATE.
16
17 The CMD_LED_COLOR command sends 5 bytes and the CMD_LED_STATE command 2
18 bytes over the I2C bus, which operates at 100 kHz. With I2C overhead
19 this allows ~1670 color changing commands and ~3200 state changing
20 commands per second (or around 1000 color + state changes per second).
21 This may seem more than enough, but the issue is that the I2C bus is
22 shared with another peripheral, the MCU. The MCU exposes an interrupt
23 interface, and it can trigger hundreds of interrupts per second. Each
24 time, we need to read the interrupt state register over this I2C bus.
25 Whenever we are sending a LED color/state changing command, the
26 interrupt reading is waiting.
27
28 Currently, every time LED brightness or LED multi intensity is changed,
29 we send a CMD_LED_STATE command, and if the computed color (brightness
30 adjusted multi_intensity) is non-zero, we also send a CMD_LED_COLOR
31 command.
32
33 Consider for example the situation when we have a netdev trigger enabled
34 for a LED. The netdev trigger does not change the LED color, only the
35 brightness (either to 0 or to currently configured brightness), and so
36 there is no need to send the CMD_LED_COLOR command. But each change of
37 brightness to 0 sends one CMD_LED_STATE command, and each change of
38 brightness to max_brightness sends one CMD_LED_STATE command and one
39 CMD_LED_COLOR command:
40 set_brightness(0) -> CMD_LED_STATE
41 set_brightness(255) -> CMD_LED_STATE + CMD_LED_COLOR
42 (unnecessary)
43
44 We can avoid the unnecessary I2C transactions if we cache the values of
45 state and color that are sent to the controller. If the color does not
46 change from the one previously sent, there is no need to do the
47 CMD_LED_COLOR I2C transaction, and if the state does not change, there
48 is no need to do the CMD_LED_STATE transaction.
49
50 Because we need to make sure that our cached values are consistent with
51 the controller state, add explicit setting of the LED color to white at
52 probe time (this is the default setting when MCU resets, but does not
53 necessarily need to be the case, for example if U-Boot played with the
54 LED colors).
55
56 Signed-off-by: Marek BehĂșn <kabel@kernel.org>
57 Link: https://lore.kernel.org/r/20230918161104.20860-3-kabel@kernel.org
58 Signed-off-by: Lee Jones <lee@kernel.org>
59 ---
60 drivers/leds/leds-turris-omnia.c | 96 ++++++++++++++++++++++++++------
61 1 file changed, 78 insertions(+), 18 deletions(-)
62
63 --- a/drivers/leds/leds-turris-omnia.c
64 +++ b/drivers/leds/leds-turris-omnia.c
65 @@ -30,6 +30,8 @@
66 struct omnia_led {
67 struct led_classdev_mc mc_cdev;
68 struct mc_subled subled_info[OMNIA_LED_NUM_CHANNELS];
69 + u8 cached_channels[OMNIA_LED_NUM_CHANNELS];
70 + bool on;
71 int reg;
72 };
73
74 @@ -72,36 +74,82 @@ static int omnia_cmd_read_u8(const struc
75 return -EIO;
76 }
77
78 +static int omnia_led_send_color_cmd(const struct i2c_client *client,
79 + struct omnia_led *led)
80 +{
81 + char cmd[5];
82 + int ret;
83 +
84 + cmd[0] = CMD_LED_COLOR;
85 + cmd[1] = led->reg;
86 + cmd[2] = led->subled_info[0].brightness;
87 + cmd[3] = led->subled_info[1].brightness;
88 + cmd[4] = led->subled_info[2].brightness;
89 +
90 + /* Send the color change command */
91 + ret = i2c_master_send(client, cmd, 5);
92 + if (ret < 0)
93 + return ret;
94 +
95 + /* Cache the RGB channel brightnesses */
96 + for (int i = 0; i < OMNIA_LED_NUM_CHANNELS; ++i)
97 + led->cached_channels[i] = led->subled_info[i].brightness;
98 +
99 + return 0;
100 +}
101 +
102 +/* Determine if the computed RGB channels are different from the cached ones */
103 +static bool omnia_led_channels_changed(struct omnia_led *led)
104 +{
105 + for (int i = 0; i < OMNIA_LED_NUM_CHANNELS; ++i)
106 + if (led->subled_info[i].brightness != led->cached_channels[i])
107 + return true;
108 +
109 + return false;
110 +}
111 +
112 static int omnia_led_brightness_set_blocking(struct led_classdev *cdev,
113 enum led_brightness brightness)
114 {
115 struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
116 struct omnia_leds *leds = dev_get_drvdata(cdev->dev->parent);
117 struct omnia_led *led = to_omnia_led(mc_cdev);
118 - u8 buf[5], state;
119 - int ret;
120 + int err = 0;
121
122 mutex_lock(&leds->lock);
123
124 - led_mc_calc_color_components(&led->mc_cdev, brightness);
125 + /*
126 + * Only recalculate RGB brightnesses from intensities if brightness is
127 + * non-zero. Otherwise we won't be using them and we can save ourselves
128 + * some software divisions (Omnia's CPU does not implement the division
129 + * instruction).
130 + */
131 + if (brightness) {
132 + led_mc_calc_color_components(mc_cdev, brightness);
133 +
134 + /*
135 + * Send color command only if brightness is non-zero and the RGB
136 + * channel brightnesses changed.
137 + */
138 + if (omnia_led_channels_changed(led))
139 + err = omnia_led_send_color_cmd(leds->client, led);
140 + }
141
142 - buf[0] = CMD_LED_COLOR;
143 - buf[1] = led->reg;
144 - buf[2] = mc_cdev->subled_info[0].brightness;
145 - buf[3] = mc_cdev->subled_info[1].brightness;
146 - buf[4] = mc_cdev->subled_info[2].brightness;
147 -
148 - state = CMD_LED_STATE_LED(led->reg);
149 - if (buf[2] || buf[3] || buf[4])
150 - state |= CMD_LED_STATE_ON;
151 -
152 - ret = omnia_cmd_write_u8(leds->client, CMD_LED_STATE, state);
153 - if (ret >= 0 && (state & CMD_LED_STATE_ON))
154 - ret = i2c_master_send(leds->client, buf, 5);
155 + /* Send on/off state change only if (bool)brightness changed */
156 + if (!err && !brightness != !led->on) {
157 + u8 state = CMD_LED_STATE_LED(led->reg);
158 +
159 + if (brightness)
160 + state |= CMD_LED_STATE_ON;
161 +
162 + err = omnia_cmd_write_u8(leds->client, CMD_LED_STATE, state);
163 + if (!err)
164 + led->on = !!brightness;
165 + }
166
167 mutex_unlock(&leds->lock);
168
169 - return ret;
170 + return err;
171 }
172
173 static int omnia_led_register(struct i2c_client *client, struct omnia_led *led,
174 @@ -129,11 +177,15 @@ static int omnia_led_register(struct i2c
175 }
176
177 led->subled_info[0].color_index = LED_COLOR_ID_RED;
178 - led->subled_info[0].channel = 0;
179 led->subled_info[1].color_index = LED_COLOR_ID_GREEN;
180 - led->subled_info[1].channel = 1;
181 led->subled_info[2].color_index = LED_COLOR_ID_BLUE;
182 - led->subled_info[2].channel = 2;
183 +
184 + /* Initial color is white */
185 + for (int i = 0; i < OMNIA_LED_NUM_CHANNELS; ++i) {
186 + led->subled_info[i].intensity = 255;
187 + led->subled_info[i].brightness = 255;
188 + led->subled_info[i].channel = i;
189 + }
190
191 led->mc_cdev.subled_info = led->subled_info;
192 led->mc_cdev.num_colors = OMNIA_LED_NUM_CHANNELS;
193 @@ -162,6 +214,14 @@ static int omnia_led_register(struct i2c
194 return ret;
195 }
196
197 + /* Set initial color and cache it */
198 + ret = omnia_led_send_color_cmd(client, led);
199 + if (ret < 0) {
200 + dev_err(dev, "Cannot set LED %pOF initial color: %i\n", np,
201 + ret);
202 + return ret;
203 + }
204 +
205 ret = devm_led_classdev_multicolor_register_ext(dev, &led->mc_cdev,
206 &init_data);
207 if (ret < 0) {