| Message ID | 20220411162033.39613-4-eajames@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | leds: pca955x: Add HW blink support | expand |
Hi! > Previously, the probe function might do up to 32 reads and writes > to the same 4 registers to program the led selection. Reduce this to > a maximum of 8 operations by accumulating the changes to the led > selection and comparing with the previous value to write the > selection if different. We have regmap APIs. You are free to use them if you really care about those few reads. Reimplementing them by hand is not acceptable. How big is the seedup here? Best regards, Pavel > @@ -554,6 +556,15 @@ static int pca955x_probe(struct i2c_client *client) > init_data.devname_mandatory = false; > init_data.devicename = "pca955x"; > > + nls = pca955x_num_led_regs(chip->bits); > + for (i = 0; i < nls; ++i) { > + err = pca955x_read_ls(pca955x, i, &ls1[i]); > + if (err) > + return err; > + > + ls2[i] = ls1[i]; > + } > + > for (i = 0; i < chip->bits; i++) { > pca955x_led = &pca955x->leds[i]; > pca955x_led->led_num = i; > @@ -624,6 +634,14 @@ static int pca955x_probe(struct i2c_client *client) > } > } > > + for (i = 0; i < nls; ++i) { > + if (ls1[i] != ls2[i]) { > + err = pca955x_write_ls(pca955x, i, ls2[i]); > + if (err) > + return err; > + } > + } > + > /* PWM0 is used for half brightness or 50% duty cycle */ > err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF); > if (err)
On 5/4/22 12:24, Pavel Machek wrote: > Hi! > >> Previously, the probe function might do up to 32 reads and writes >> to the same 4 registers to program the led selection. Reduce this to >> a maximum of 8 operations by accumulating the changes to the led >> selection and comparing with the previous value to write the >> selection if different. > We have regmap APIs. You are free to use them if you really care about > those few reads. Reimplementing them by hand is not acceptable. How big is > the seedup here? Hi, To be honest this was not about speed, it's about a problem I've observed where many operations in quick succession caused the PCA chip to NAK the i2c transfer. I'm not sure of the root cause yet. So reducing the number of operations helped. We are also probably going to carry a throttling patch, unless I can prove the PCA chip itself is at fault and needs slower transfers. I can try the regmap API and see if it helps though. Thanks, Eddie > > Best regards, > Pavel > >> @@ -554,6 +556,15 @@ static int pca955x_probe(struct i2c_client *client) >> init_data.devname_mandatory = false; >> init_data.devicename = "pca955x"; >> >> + nls = pca955x_num_led_regs(chip->bits); >> + for (i = 0; i < nls; ++i) { >> + err = pca955x_read_ls(pca955x, i, &ls1[i]); >> + if (err) >> + return err; >> + >> + ls2[i] = ls1[i]; >> + } >> + >> for (i = 0; i < chip->bits; i++) { >> pca955x_led = &pca955x->leds[i]; >> pca955x_led->led_num = i; >> @@ -624,6 +634,14 @@ static int pca955x_probe(struct i2c_client *client) >> } >> } >> >> + for (i = 0; i < nls; ++i) { >> + if (ls1[i] != ls2[i]) { >> + err = pca955x_write_ls(pca955x, i, ls2[i]); >> + if (err) >> + return err; >> + } >> + } >> + >> /* PWM0 is used for half brightness or 50% duty cycle */ >> err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF); >> if (err)
diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c index cb1895b79eab..61f3cb84a945 100644 --- a/drivers/leds/leds-pca955x.c +++ b/drivers/leds/leds-pca955x.c @@ -483,7 +483,9 @@ static int pca955x_probe(struct i2c_client *client) struct led_classdev *led; struct led_init_data init_data; struct i2c_adapter *adapter; - int i, err; + int i, bit, err, nls, reg; + u8 ls1[4]; + u8 ls2[4]; struct pca955x_platform_data *pdata; bool set_default_label = false; bool keep_pwm = false; @@ -554,6 +556,15 @@ static int pca955x_probe(struct i2c_client *client) init_data.devname_mandatory = false; init_data.devicename = "pca955x"; + nls = pca955x_num_led_regs(chip->bits); + for (i = 0; i < nls; ++i) { + err = pca955x_read_ls(pca955x, i, &ls1[i]); + if (err) + return err; + + ls2[i] = ls1[i]; + } + for (i = 0; i < chip->bits; i++) { pca955x_led = &pca955x->leds[i]; pca955x_led->led_num = i; @@ -565,21 +576,20 @@ static int pca955x_probe(struct i2c_client *client) case PCA955X_TYPE_GPIO: break; case PCA955X_TYPE_LED: + bit = i % 4; + reg = i / 4; led = &pca955x_led->led_cdev; led->brightness_set_blocking = pca955x_led_set; led->brightness_get = pca955x_led_get; if (pdata->leds[i].default_state == - LEDS_GPIO_DEFSTATE_OFF) { - err = pca955x_led_set(led, LED_OFF); - if (err) - return err; - } else if (pdata->leds[i].default_state == - LEDS_GPIO_DEFSTATE_ON) { - err = pca955x_led_set(led, LED_FULL); - if (err) - return err; - } + LEDS_GPIO_DEFSTATE_OFF) + ls2[reg] = pca955x_ledsel(ls2[reg], bit, + PCA955X_LS_LED_OFF); + else if (pdata->leds[i].default_state == + LEDS_GPIO_DEFSTATE_ON) + ls2[reg] = pca955x_ledsel(ls2[reg], bit, + PCA955X_LS_LED_ON); init_data.fwnode = pdata->leds[i].fwnode; @@ -624,6 +634,14 @@ static int pca955x_probe(struct i2c_client *client) } } + for (i = 0; i < nls; ++i) { + if (ls1[i] != ls2[i]) { + err = pca955x_write_ls(pca955x, i, ls2[i]); + if (err) + return err; + } + } + /* PWM0 is used for half brightness or 50% duty cycle */ err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF); if (err)
Previously, the probe function might do up to 32 reads and writes to the same 4 registers to program the led selection. Reduce this to a maximum of 8 operations by accumulating the changes to the led selection and comparing with the previous value to write the selection if different. Signed-off-by: Eddie James <eajames@linux.ibm.com> --- drivers/leds/leds-pca955x.c | 40 +++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 11 deletions(-)