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Date: Sat, 7 Jan 2012 16:16:37 +0530
From: Thomas Abraham <thomas.abraham@...aro.org>
To: Lars-Peter Clausen <lars@...afoo.de>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
rpurdie@...ys.net, linux-samsung-soc@...r.kernel.org,
grant.likely@...retlab.ca, rob.herring@...xeda.com,
kgene.kim@...sung.com, jg1.han@...sung.com,
broonie@...nsource.wolfsonmicro.com, kyungmin.park@...sung.com,
cbou@...l.ru, kwangwoo.lee@...il.com, augulis.darius@...il.com,
ben-linux@...ff.org, patches@...aro.org
Subject: Re: [PATCH] backlight: lcd: add driver for raster-type lcd's with
gpio controlled panel reset
Hi Lars,
On 6 January 2012 00:37, Lars-Peter Clausen <lars@...afoo.de> wrote:
>> [...]
>>
>> diff --git a/Documentation/devicetree/bindings/lcd/lcd-pwrctrl.txt b/Documentation/devicetree/bindings/lcd/lcd-pwrctrl.txt
[...]
>> +Optional properties:
>> +- lcd,pwrctrl-nreset-gpio-invert: When the nRESET line is asserted low, the
>> + lcd panel is reset and stays in reset mode as long as the nRESET line is
>> + asserted low. This is the default behaviour of most lcd panels. If a lcd
>> + panel requires the nRESET line to be asserted high for panel reset, then
>> + this property is used.
>
> Maybe use OF_GPIO_ACTIVE_LOW here instead. That would make active high the
> default but be a bit more consistent.
Thanks for pointing this out. But most of these panels have active low
RESET line. So OF_GPIO_ACTIVE_LOW will need to be added for every lcd
node in dts file. How about adding a new 'OF_GPIO_ACTIVE_HIGH' instead
and keeping active-low the default?
>
>> +- lcd,pwrctrl-min-uV: If a regulator controls the Vcc voltage of the lcd panel,
>> + this property specifies the minimum voltage the regulator should supply.
>> + The value of this property should in in micro-volts.
>> +- lcd,pwrctrl-max-uV: If a regulator controls the Vcc voltage of the lcd panel,
>> + this property specifies the maximum voltage the regulator should limit to
>> + on the Vcc line. The value of this property should in in micro-volts.
>
> The min and max voltage should rather be specified through the regulator
> constraints.
The min and max voltage is a panel specific property which is used to
configure the regulator. The regulator might be capable of a larger
range but these value is used to setup the regulator to output a
voltage suitable for the panel.
>
>
>> +- vcc-lcd-supply: phandle of the regulator that controls the vcc supply to
>> + the lcd panel.
>> +
> [...]
>> diff --git a/drivers/video/backlight/lcd_pwrctrl.c b/drivers/video/backlight/lcd_pwrctrl.c
>> new file mode 100644
>> index 0000000..6f3110b
>> --- /dev/null
>> +++ b/drivers/video/backlight/lcd_pwrctrl.c
>> @@ -0,0 +1,231 @@
>> [...]
>> +static int lcd_pwrctrl_set_power(struct lcd_device *lcd, int power)
>> +{
>> + struct lcd_pwrctrl *lp = lcd_get_data(lcd);
>> + struct lcd_pwrctrl_data *pd = lp->pdata;
>> + int lcd_enable, lcd_reset;
>> +
>> + lcd_enable = (power == FB_BLANK_POWERDOWN || lp->suspended) ? 0 : 1;
>> + lcd_reset = (pd->invert) ? !lcd_enable : lcd_enable;
>> +
>> + if (IS_ERR(lp->regulator))
>> + goto no_regulator;
>
> I wouldn't use a goto here.
Ok. I was not happy either while writing it. I will re-work this.
>
>> +
>> + if (lcd_enable) {
>> + if ((pd->min_uV || pd->max_uV) &&
>> + regulator_set_voltage(lp->regulator,
>> + pd->min_uV, pd->max_uV))
>> + dev_info(lp->dev,
>> + "regulator voltage set failed\n");
>> + if (regulator_enable(lp->regulator))
>> + dev_info(lp->dev, "failed to enable regulator\n");
>> + } else {
>> + regulator_disable(lp->regulator);
>> + }
>
> I think you have to make sure that the regulator enable and disable calls are
> balanced.
Ok. I was check on this and do required changes.
>
>> +
>> + no_regulator:
>> + gpio_direction_output(lp->pdata->gpio, lcd_reset);
>> + lp->power = power;
>> + return 0;
>> +}
>> +
> [...]
>> +
>> +#ifdef CONFIG_OF
>
> I think you can remove all the CONFIG_OF ifdefs, the of API should stub itself out.
This #ifdef is to keep the OF code out in case of non-OF only compilation.
[...]
>> + err = gpio_request(pdata->gpio, "LCD-nRESET");
>> + if (err) {
>> + dev_err(dev, "gpio [%d] request failed\n", pdata->gpio);
>> + return err;
>> + }
>> +
>> + lp = devm_kzalloc(dev, sizeof(struct lcd_pwrctrl), GFP_KERNEL);
>> + if (!lp) {
>> + dev_err(dev, "memory allocation failed for private data\n");
>> + return -ENOMEM;
>
> You are leaking the gpio here.
Ok. I will fix this.
>
>> + }
>> +
>> + /*
>> + * If power to lcd and/or lcd interface is controlled using a regulator,
>> + * get the handle to the regulator for later use during power switching.
>> + */
>> + lp->regulator = regulator_get(dev, "vcc-lcd");
>> + if (IS_ERR(lp->regulator))
>> + dev_info(dev, "could not find regulator\n");
>> +
>> + lp->dev = dev;
>> + lp->pdata = pdata;
>> + lp->lcd = lcd_device_register(dev_name(dev), dev, lp, &lcd_pwrctrl_ops);
>> + if (IS_ERR(lp->lcd)) {
>> + dev_err(dev, "cannot register lcd device\n");
>> + regulator_put(lp->regulator);
>
> And here.
Ok. I will fix this.
>
>> + return PTR_ERR(lp->lcd);
>> + }
>> +
>> + platform_set_drvdata(pdev, lp);
>> + lcd_pwrctrl_set_power(lp->lcd, FB_BLANK_NORMAL);
>> + return 0;
>> +}
>> +
>> +#ifdef CONFIG_OF
>> +static const struct of_device_id lcd_pwrctrl_match[] = {
>> + { .compatible = "lcd,powerctrl", },
>> + {},
>> +};
>
> MODULE_DEVICE_TABLE(...)
Right. I missed that.
>
>> +#endif
>
>
>> +static struct platform_driver lcd_pwrctrl_driver = {
>> + .driver = {
>> + .name = "lcd-pwrctrl",
>> + .owner = THIS_MODULE,
>> + .of_match_table = of_match_ptr(lcd_pwrctrl_match),
>> + },
>> + .probe = lcd_pwrctrl_probe,
>> + .remove = lcd_pwrctrl_remove,
>> + .suspend = lcd_pwrctrl_suspend,
>> + .resume = lcd_pwrctrl_resume,
>
> please use dev_pm_ops instead of the legacy callbacks
Ok. I will use dev_pm_ops here.
[...]
Thanks for your review Lars.
Regards,
Thomas.
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