diff options
| -rw-r--r-- | drivers/leds/leds-tca6507.c | 190 |
1 files changed, 102 insertions, 88 deletions
diff --git a/drivers/leds/leds-tca6507.c b/drivers/leds/leds-tca6507.c index 93a2b175905..503df834c69 100644 --- a/drivers/leds/leds-tca6507.c +++ b/drivers/leds/leds-tca6507.c @@ -4,77 +4,87 @@ * The TCA6507 is a programmable LED controller that can drive 7 * separate lines either by holding them low, or by pulsing them * with modulated width. - * The modulation can be varied in a simple pattern to produce a blink or - * double-blink. + * The modulation can be varied in a simple pattern to produce a + * blink or double-blink. * - * This driver can configure each line either as a 'GPIO' which is out-only - * (no pull-up) or as an LED with variable brightness and hardware-assisted - * blinking. + * This driver can configure each line either as a 'GPIO' which is + * out-only (pull-up resistor required) or as an LED with variable + * brightness and hardware-assisted blinking. * - * Apart from OFF and ON there are three programmable brightness levels which - * can be programmed from 0 to 15 and indicate how many 500usec intervals in - * each 8msec that the led is 'on'. The levels are named MASTER, BANK0 and - * BANK1. + * Apart from OFF and ON there are three programmable brightness + * levels which can be programmed from 0 to 15 and indicate how many + * 500usec intervals in each 8msec that the led is 'on'. The levels + * are named MASTER, BANK0 and BANK1. * - * There are two different blink rates that can be programmed, each with - * separate time for rise, on, fall, off and second-off. Thus if 3 or more - * different non-trivial rates are required, software must be used for the extra - * rates. The two different blink rates must align with the two levels BANK0 and - * BANK1. - * This driver does not support double-blink so 'second-off' always matches - * 'off'. + * There are two different blink rates that can be programmed, each + * with separate time for rise, on, fall, off and second-off. Thus if + * 3 or more different non-trivial rates are required, software must + * be used for the extra rates. The two different blink rates must + * align with the two levels BANK0 and BANK1. This driver does not + * support double-blink so 'second-off' always matches 'off'. * - * Only 16 different times can be programmed in a roughly logarithmic scale from - * 64ms to 16320ms. To be precise the possible times are: + * Only 16 different times can be programmed in a roughly logarithmic + * scale from 64ms to 16320ms. To be precise the possible times are: * 0, 64, 128, 192, 256, 384, 512, 768, * 1024, 1536, 2048, 3072, 4096, 5760, 8128, 16320 * - * Times that cannot be closely matched with these must be - * handled in software. This driver allows 12.5% error in matching. + * Times that cannot be closely matched with these must be handled in + * software. This driver allows 12.5% error in matching. * - * This driver does not allow rise/fall rates to be set explicitly. When trying - * to match a given 'on' or 'off' period, an appropriate pair of 'change' and - * 'hold' times are chosen to get a close match. If the target delay is even, - * the 'change' number will be the smaller; if odd, the 'hold' number will be - * the smaller. - - * Choosing pairs of delays with 12.5% errors allows us to match delays in the - * ranges: 56-72, 112-144, 168-216, 224-27504, 28560-36720. - * 26% of the achievable sums can be matched by multiple pairings. For example - * 1536 == 1536+0, 1024+512, or 768+768. This driver will always choose the - * pairing with the least maximum - 768+768 in this case. Other pairings are - * not available. + * This driver does not allow rise/fall rates to be set explicitly. + * When trying to match a given 'on' or 'off' period, an appropriate + * pair of 'change' and 'hold' times are chosen to get a close match. + * If the target delay is even, the 'change' number will be the + * smaller; if odd, the 'hold' number will be the smaller. + + * Choosing pairs of delays with 12.5% errors allows us to match + * delays in the ranges: 56-72, 112-144, 168-216, 224-27504, + * 28560-36720. + * 26% of the achievable sums can be matched by multiple pairings. + * For example 1536 == 1536+0, 1024+512, or 768+768. + * This driver will always choose the pairing with the least + * maximum - 768+768 in this case. Other pairings are not available. * - * Access to the 3 levels and 2 blinks are on a first-come, first-served basis. - * Access can be shared by multiple leds if they have the same level and - * either same blink rates, or some don't blink. - * When a led changes, it relinquishes access and tries again, so it might - * lose access to hardware blink. - * If a blink engine cannot be allocated, software blink is used. - * If the desired brightness cannot be allocated, the closest available non-zero - * brightness is used. As 'full' is always available, the worst case would be - * to have two different blink rates at '1', with Max at '2', then other leds - * will have to choose between '2' and '16'. Hopefully this is not likely. + * Access to the 3 levels and 2 blinks are on a first-come, + * first-served basis. Access can be shared by multiple leds if they + * have the same level and either same blink rates, or some don't + * blink. When a led changes, it relinquishes access and tries again, + * so it might lose access to hardware blink. * - * Each bank (BANK0 and BANK1) has two usage counts - LEDs using the brightness - * and LEDs using the blink. It can only be reprogrammed when the appropriate - * counter is zero. The MASTER level has a single usage count. + * If a blink engine cannot be allocated, software blink is used. If + * the desired brightness cannot be allocated, the closest available + * non-zero brightness is used. As 'full' is always available, the + * worst case would be to have two different blink rates at '1', with + * Max at '2', then other leds will have to choose between '2' and + * '16'. Hopefully this is not likely. * - * Each Led has programmable 'on' and 'off' time as milliseconds. With each - * there is a flag saying if it was explicitly requested or defaulted. - * Similarly the banks know if each time was explicit or a default. Defaults - * are permitted to be changed freely - they are not recognised when matching. + * Each bank (BANK0 and BANK1) has two usage counts - LEDs using the + * brightness and LEDs using the blink. It can only be reprogrammed + * when the appropriate counter is zero. The MASTER level has a + * single usage count. * + * Each LED has programmable 'on' and 'off' time as milliseconds. + * With each there is a flag saying if it was explicitly requested or + * defaulted. Similarly the banks know if each time was explicit or a + * default. Defaults are permitted to be changed freely - they are + * not recognised when matching. * - * An led-tca6507 device must be provided with platform data. This data - * lists for each output: the name, default trigger, and whether the signal - * is being used as a GPiO rather than an led. 'struct led_plaform_data' - * is used for this. If 'name' is NULL, the output isn't used. If 'flags' - * is TCA6507_MAKE_CPIO, the output is a GPO. - * The "struct led_platform_data" can be embedded in a - * "struct tca6507_platform_data" which adds a 'gpio_base' for the GPiOs, - * and a 'setup' callback which is called once the GPiOs are available. * + * An led-tca6507 device must be provided with platform data or + * configured via devicetree. + * + * The platform-data lists for each output: the name, default trigger, + * and whether the signal is being used as a GPIO rather than an LED. + * 'struct led_plaform_data' is used for this. If 'name' is NULL, the + * output isn't used. If 'flags' is TCA6507_MAKE_GPIO, the output is + * a GPO. The "struct led_platform_data" can be embedded in a "struct + * tca6507_platform_data" which adds a 'gpio_base' for the GPIOs, and + * a 'setup' callback which is called once the GPIOs are available. + * + * When configured via devicetree there is one child for each output. + * The "reg" determines the output number and "compatible" determines + * whether it is an LED or a GPIO. "linux,default-trigger" can set a + * default trigger. */ #include <linux/module.h> @@ -192,17 +202,18 @@ MODULE_DEVICE_TABLE(i2c, tca6507_id); static int choose_times(int msec, int *c1p, int *c2p) { /* - * Choose two timecodes which add to 'msec' as near as possible. - * The first returned is the 'on' or 'off' time. The second is to be - * used as a 'fade-on' or 'fade-off' time. If 'msec' is even, - * the first will not be smaller than the second. If 'msec' is odd, - * the first will not be larger than the second. - * If we cannot get a sum within 1/8 of 'msec' fail with -EINVAL, - * otherwise return the sum that was achieved, plus 1 if the first is - * smaller. - * If two possibilities are equally good (e.g. 512+0, 256+256), choose - * the first pair so there is more change-time visible (i.e. it is - * softer). + * Choose two timecodes which add to 'msec' as near as + * possible. The first returned is the 'on' or 'off' time. + * The second is to be used as a 'fade-on' or 'fade-off' time. + * If 'msec' is even, the first will not be smaller than the + * second. If 'msec' is odd, the first will not be larger + * than the second. + * If we cannot get a sum within 1/8 of 'msec' fail with + * -EINVAL, otherwise return the sum that was achieved, plus 1 + * if the first is smaller. + * If two possibilities are equally good (e.g. 512+0, + * 256+256), choose the first pair so there is more + * change-time visible (i.e. it is softer). */ int c1, c2; int tmax = msec * 9 / 8; @@ -255,8 +266,8 @@ static int choose_times(int msec, int *c1p, int *c2p) } /* - * Update the register file with the appropriate 3-bit state for - * the given led. + * Update the register file with the appropriate 3-bit state for the + * given led. */ static void set_select(struct tca6507_chip *tca, int led, int val) { @@ -274,9 +285,9 @@ static void set_select(struct tca6507_chip *tca, int led, int val) } } -/* Update the register file with the appropriate 4-bit code for - * one bank or other. This can be used for timers, for levels, or - * for initialisation. +/* Update the register file with the appropriate 4-bit code for one + * bank or other. This can be used for timers, for levels, or for + * initialization. */ static void set_code(struct tca6507_chip *tca, int reg, int bank, int new) { @@ -309,7 +320,7 @@ static void set_level(struct tca6507_chip *tca, int bank, int level) tca->bank[bank].level = level; } -/* Record all relevant time code for a given bank */ +/* Record all relevant time codes for a given bank */ static void set_times(struct tca6507_chip *tca, int bank) { int c1, c2; @@ -317,7 +328,8 @@ static void set_times(struct tca6507_chip *tca, int bank) result = choose_times(tca->bank[bank].ontime, &c1, &c2); dev_dbg(&tca->client->dev, - "Chose on times %d(%d) %d(%d) for %dms\n", c1, time_codes[c1], + "Chose on times %d(%d) %d(%d) for %dms\n", + c1, time_codes[c1], c2, time_codes[c2], tca->bank[bank].ontime); set_code(tca, TCA6507_FADE_ON, bank, c2); set_code(tca, TCA6507_FULL_ON, bank, c1); @@ -325,7 +337,8 @@ static void set_times(struct tca6507_chip *tca, int bank) result = choose_times(tca->bank[bank].offtime, &c1, &c2); dev_dbg(&tca->client->dev, - "Chose off times %d(%d) %d(%d) for %dms\n", c1, time_codes[c1], + "Chose off times %d(%d) %d(%d) for %dms\n", + c1, time_codes[c1], c2, time_codes[c2], tca->bank[bank].offtime); set_code(tca, TCA6507_FADE_OFF, bank, c2); set_code(tca, TCA6507_FIRST_OFF, bank, c1); @@ -373,7 +386,8 @@ static void led_release(struct tca6507_led *led) static int led_prepare(struct tca6507_led *led) { - /* Assign this led to a bank, configuring that bank if necessary. */ + /* Assign this led to a bank, configuring that bank if + * necessary. */ int level = TO_LEVEL(led->led_cdev.brightness); struct tca6507_chip *tca = led->chip; int c1, c2; @@ -389,10 +403,10 @@ static int led_prepare(struct tca6507_led *led) if (led->ontime == 0 || led->offtime == 0) { /* - * Just set the brightness, choosing first usable bank. - * If none perfect, choose best. - * Count backwards so we check MASTER bank first - * to avoid wasting a timer. + * Just set the brightness, choosing first usable + * bank. If none perfect, choose best. Count + * backwards so we check MASTER bank first to avoid + * wasting a timer. */ int best = -1;/* full-on */ int diff = 15-level; @@ -433,9 +447,9 @@ static int led_prepare(struct tca6507_led *led) } /* - * We have on/off time so we need to try to allocate a timing bank. - * First check if times are compatible with hardware and give up if - * not. + * We have on/off time so we need to try to allocate a timing + * bank. First check if times are compatible with hardware + * and give up if not. */ if (choose_times(led->ontime, &c1, &c2) < 0) return -EINVAL; @@ -523,8 +537,8 @@ static int led_assign(struct tca6507_led *led) err = led_prepare(led); if (err) { /* - * Can only fail on timer setup. In that case we need to - * re-establish as steady level. + * Can only fail on timer setup. In that case we need + * to re-establish as steady level. */ led->ontime = 0; led->offtime = 0; @@ -594,8 +608,8 @@ static void tca6507_gpio_set_value(struct gpio_chip *gc, spin_lock_irqsave(&tca->lock, flags); /* - * 'OFF' is floating high, and 'ON' is pulled down, so it has the - * inverse sense of 'val'. + * 'OFF' is floating high, and 'ON' is pulled down, so it has + * the inverse sense of 'val'. */ set_select(tca, tca->gpio_map[offset], val ? TCA6507_LS_LED_OFF : TCA6507_LS_LED_ON); |