linux-kernel - Re: [PATCH v2] spi: atmel: use managed resource for gpio chip select

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Date:   Wed, 9 Nov 2016 10:16:18 +0100
From:   Nicolas Ferre <nicolas.ferre@...el.com>
To:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Mark Brown <broonie@...nel.org>
CC:     <linux@...tdown.ru>,
        Boris BREZILLON <boris.brezillon@...e-electrons.com>,
        <linux-spi@...r.kernel.org>, <geert@...ux-m68k.org>,
        Ludovic Desroches <ludovic.desroches@...el.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        Wenyou Yang <wenyou.yang@...el.com>
Subject: Re: [PATCH v2] spi: atmel: use managed resource for gpio chip select

Le 08/11/2016 à 18:49, Alexandre Belloni a écrit :
> On 08/11/2016 at 18:48:52 +0100, Nicolas Ferre wrote :
>> Use the managed gpio CS pin request so that we avoid having trouble
>> in the cleanup code.
>> In fact, if module was configured with DT, cleanup code released
>> invalid pin.  Since resource wasn't freed, module cannot be reinserted.
>>
>> This require to extract the gpio request call from the "setup" function
>> and call it in the appropriate probe function.
>>
>> Reported-by: Alexander Morozov <linux@...tdown.ru>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
> 
> I think that's fine but I still have that item on my todo list
> (discussion in july 2014 with Mark):
> 
> ---
>>> Mark: maybe it would make sense to do devm_gpio_request_one() in
>>> of_spi_register_master(), after of_get_named_gpio.
> 
>> You need to transition all the drivers doing things manually but yes.
>> As I keep saying all the GPIO handling needs to be completely
>> refactored.
> ---

Would make sense indeed as we are currently doing the same node scanning
twice...

But this patch actually fixes an issue with module unloading/re-loading
and freeing of a wrong gpio. So I do think that we shouldn't hold its
adoption while thinking about this enhancement...

Regards,

>> ---
>> v2: fix devm_gpio_request location: the setup code for device was not proper
>>     location. Move it to the probe function and add needed DT routines to
>>     handle all CS gpio specified.
>>
>>  drivers/spi/spi-atmel.c | 50 ++++++++++++++++++++++++++++++++++++++-----------
>>  1 file changed, 39 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
>> index 32683a13dd60..a60925614480 100644
>> --- a/drivers/spi/spi-atmel.c
>> +++ b/drivers/spi/spi-atmel.c
>> @@ -24,6 +24,7 @@
>>  
>>  #include <linux/io.h>
>>  #include <linux/gpio.h>
>> +#include <linux/of_gpio.h>
>>  #include <linux/pinctrl/consumer.h>
>>  #include <linux/pm_runtime.h>
>>  
>> @@ -1204,7 +1205,6 @@ static int atmel_spi_setup(struct spi_device *spi)
>>  	u32			csr;
>>  	unsigned int		bits = spi->bits_per_word;
>>  	unsigned int		npcs_pin;
>> -	int			ret;
>>  
>>  	as = spi_master_get_devdata(spi->master);
>>  
>> @@ -1247,16 +1247,9 @@ static int atmel_spi_setup(struct spi_device *spi)
>>  		if (!asd)
>>  			return -ENOMEM;
>>  
>> -		if (as->use_cs_gpios) {
>> -			ret = gpio_request(npcs_pin, dev_name(&spi->dev));
>> -			if (ret) {
>> -				kfree(asd);
>> -				return ret;
>> -			}
>> -
>> +		if (as->use_cs_gpios)
>>  			gpio_direction_output(npcs_pin,
>>  					      !(spi->mode & SPI_CS_HIGH));
>> -		}
>>  
>>  		asd->npcs_pin = npcs_pin;
>>  		spi->controller_state = asd;
>> @@ -1471,13 +1464,11 @@ static int atmel_spi_transfer_one_message(struct spi_master *master,
>>  static void atmel_spi_cleanup(struct spi_device *spi)
>>  {
>>  	struct atmel_spi_device	*asd = spi->controller_state;
>> -	unsigned		gpio = (unsigned long) spi->controller_data;
>>  
>>  	if (!asd)
>>  		return;
>>  
>>  	spi->controller_state = NULL;
>> -	gpio_free(gpio);
>>  	kfree(asd);
>>  }
>>  
>> @@ -1499,6 +1490,39 @@ static void atmel_get_caps(struct atmel_spi *as)
>>  }
>>  
>>  /*-------------------------------------------------------------------------*/
>> +static int atmel_spi_gpio_cs(struct platform_device *pdev)
>> +{
>> +	struct spi_master	*master = platform_get_drvdata(pdev);
>> +	struct atmel_spi	*as = spi_master_get_devdata(master);
>> +	struct device_node	*np = master->dev.of_node;
>> +	int			i;
>> +	int			ret = 0;
>> +	int			nb = 0;
>> +
>> +	if (!as->use_cs_gpios)
>> +		return 0;
>> +
>> +	if (!np)
>> +		return 0;
>> +
>> +	nb = of_gpio_named_count(np, "cs-gpios");
>> +	for (i = 0; i < nb; i++) {
>> +		int cs_gpio = of_get_named_gpio(pdev->dev.of_node,
>> +						"cs-gpios", i);
>> +
>> +			if (cs_gpio == -EPROBE_DEFER)
>> +				return cs_gpio;
>> +
>> +			if (gpio_is_valid(cs_gpio)) {
>> +				ret = devm_gpio_request(&pdev->dev, cs_gpio,
>> +							dev_name(&pdev->dev));
>> +				if (ret)
>> +					return ret;
>> +			}
>> +	}
>> +
>> +	return 0;
>> +}
>>  
>>  static int atmel_spi_probe(struct platform_device *pdev)
>>  {
>> @@ -1577,6 +1601,10 @@ static int atmel_spi_probe(struct platform_device *pdev)
>>  		master->num_chipselect = 4;
>>  	}
>>  
>> +	ret = atmel_spi_gpio_cs(pdev);
>> +	if (ret)
>> +		goto out_unmap_regs;
>> +
>>  	as->use_dma = false;
>>  	as->use_pdc = false;
>>  	if (as->caps.has_dma_support) {
>> -- 
>> 2.9.0
>>
> 


-- 
Nicolas Ferre