linux-kernel - Re: [PATCH 4/4] ARM: mxs: cfa10036: Fixup OLED display reset polarity

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Date:   Thu, 20 Dec 2018 11:39:12 +0000
From:   Vokáč Michal <Michal.Vokac@...ft.com>
To:     Rob Herring <robh@...nel.org>
CC:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 4/4] ARM: mxs: cfa10036: Fixup OLED display reset polarity

On 19.12.2018 18:29, Rob Herring wrote:
> On Tue, Dec 04, 2018 at 03:03:40PM +0000, Vokáč Michal wrote:
>> There was a bug in reset signal generation in ssd1307fb OLED driver.
>> The display needs an active-low reset signal but the driver produced
>> the correct sequence only if the GPIO used for reset was specified as
>> GPIO_ACTIVE_HIGH.
>>
>> Now as the OLED driver is fixed it is also necessarry to implement
>> a fixup for all current users of the old DT ABI. There is only one
>> in-tree user and that is the Crystalfontz CFA-10036 board. In case
>> this board is booting and GPIO_ACTIVE_HIGH is used for reset we
>> override it to GPIO_ACTIVE_LOW.
>>
>> Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
>> ---
>>   arch/arm/mach-mxs/mach-mxs.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 45 insertions(+)
>>
>> diff --git a/arch/arm/mach-mxs/mach-mxs.c b/arch/arm/mach-mxs/mach-mxs.c
>> index 1c6062d..23c260c 100644
>> --- a/arch/arm/mach-mxs/mach-mxs.c
>> +++ b/arch/arm/mach-mxs/mach-mxs.c
>> @@ -21,6 +21,7 @@
>>   #include <linux/reboot.h>
>>   #include <linux/micrel_phy.h>
>>   #include <linux/of_address.h>
>> +#include <linux/of_gpio.h>
>>   #include <linux/of_platform.h>
>>   #include <linux/phy.h>
>>   #include <linux/pinctrl/consumer.h>
>> @@ -268,9 +269,53 @@ static void __init apx4devkit_init(void)
>>   					   apx4devkit_phy_fixup);
>>   }
>>   
>> +#define OLED_RESET_GPIO_LEN	3
>> +#define OLED_RESET_GPIO_SIZE	(OLED_RESET_GPIO_LEN * sizeof(u32))
>> +
>> +static void __init crystalfontz_oled_reset_fixup(void)
>> +{
>> +	struct property *newgpio;
>> +	struct device_node *np;
>> +	u32 *gpiospec;
>> +	int i, ret;
>> +
>> +	np = of_find_compatible_node(NULL, NULL, "solomon,ssd1306fb-i2c");
>> +	if (!np)
>> +		return;
>> +
>> +	newgpio = kzalloc(sizeof(*newgpio) + OLED_RESET_GPIO_SIZE, GFP_KERNEL);
>> +	if (!newgpio)
>> +		return;
>> +
>> +	newgpio->value = newgpio + 1;
>> +	newgpio->length = OLED_RESET_GPIO_SIZE;
>> +	newgpio->name = kstrdup("reset-gpios", GFP_KERNEL);
>> +	if (!newgpio->name) {
>> +		kfree(newgpio);
>> +		return;
>> +	}
>> +
>> +	gpiospec = newgpio->value;
>> +	for (i = 0; i < OLED_RESET_GPIO_LEN; i++) {
>> +		ret = of_property_read_u32_index(np, "reset-gpios", i,
>> +						 &gpiospec[i]);
> 
> Don't we have a helper to read the whole array?

Hi Rob,
yep, I will fix this.
Thank you for your review and for pointing me to the right solution.

Michal

> 
> Otherwise, for the series:
> 
> Reviewed-by: Rob Herring <robh@...nel.org>
> 
>> +		if (ret) {
>> +			kfree(newgpio);
>> +			return;
>> +		}
>> +	}
>> +
>> +	if (!(gpiospec[2] & OF_GPIO_ACTIVE_LOW)) {
>> +		gpiospec[2] |= OF_GPIO_ACTIVE_LOW;
>> +		cpu_to_be32_array(gpiospec, gpiospec, OLED_RESET_GPIO_LEN);
>> +		of_update_property(np, newgpio);
>> +	}
>> +}
>> +
>>   static void __init crystalfontz_init(void)
>>   {
>>   	update_fec_mac_prop(OUI_CRYSTALFONTZ);
>> +	crystalfontz_oled_reset_fixup();
>>   }
>>   
>>   static void __init duckbill_init(void)
>> -- 
>> 2.1.4
>>