Re: [PATCH v3 18/27] mtd: nand: omap2: Implement NAND ready using gpiolib

[Roger Quadros <rogerq@ti.com>]

On 26/10/15 22:49, Brian Norris wrote:
> + others
> 
> A few comments below.
> 
> On Fri, Sep 18, 2015 at 05:53:40PM +0300, Roger Quadros wrote:
>> The GPMC WAIT pin status are now available over gpiolib.
>> Update the omap_dev_ready() function to use gpio instead of
>> directly accessing GPMC register space.
>>
>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>> ---
>>  drivers/mtd/nand/omap2.c                     | 29 +++++++++++++++++-----------
>>  include/linux/platform_data/mtd-nand-omap2.h |  2 +-
>>  2 files changed, 19 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
>> index 228f498..d0f2620 100644
>> --- a/drivers/mtd/nand/omap2.c
>> +++ b/drivers/mtd/nand/omap2.c
>> @@ -12,6 +12,7 @@
>>  #include <linux/dmaengine.h>
>>  #include <linux/dma-mapping.h>
>>  #include <linux/delay.h>
>> +#include <linux/gpio/consumer.h>
>>  #include <linux/module.h>
>>  #include <linux/interrupt.h>
>>  #include <linux/jiffies.h>
>> @@ -184,6 +185,8 @@ struct omap_nand_info {
>>  	/* fields specific for BCHx_HW ECC scheme */
>>  	struct device			*elm_dev;
>>  	struct device_node		*of_node;
>> +	/* NAND ready gpio */
>> +	struct gpio_desc		*ready_gpiod;
>>  };
>>  
>>  /**
>> @@ -1047,22 +1050,17 @@ static int omap_wait(struct mtd_info *mtd, struct nand_chip *chip)
>>  }
>>  
>>  /**
>> - * omap_dev_ready - calls the platform specific dev_ready function
>> + * omap_dev_ready - checks the NAND Ready GPIO line
>>   * @mtd: MTD device structure
>> + *
>> + * Returns true if ready and false if busy.
>>   */
>>  static int omap_dev_ready(struct mtd_info *mtd)
>>  {
>> -	unsigned int val = 0;
>>  	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
>>  							mtd);
>>  
>> -	val = readl(info->reg.gpmc_status);
>> -
>> -	if ((val & 0x100) == 0x100) {
>> -		return 1;
>> -	} else {
>> -		return 0;
>> -	}
>> +	return gpiod_get_value(info->ready_gpiod);
>>  }
>>  
>>  /**
>> @@ -1782,7 +1780,9 @@ static int omap_nand_probe(struct platform_device *pdev)
>>  		info->reg = pdata->reg;
>>  		info->of_node = pdata->of_node;
>>  		info->ecc_opt = pdata->ecc_opt;
>> -		info->dev_ready	= pdata->dev_ready;
>> +		if (pdata->dev_ready)
>> +			dev_info(&pdev->dev, "pdata->dev_ready is deprecated\n");
>> +
>>  		info->xfer_type = pdata->xfer_type;
>>  		info->devsize = pdata->devsize;
>>  		info->elm_of_node = pdata->elm_of_node;
>> @@ -1815,6 +1815,13 @@ static int omap_nand_probe(struct platform_device *pdev)
>>  	nand_chip->IO_ADDR_W = nand_chip->IO_ADDR_R;
>>  	nand_chip->cmd_ctrl  = omap_hwcontrol;
>>  
>> +	info->ready_gpiod = devm_gpiod_get_optional(&pdev->dev, "ready",
>> +						    GPIOD_IN);
> 
> Others have been looking at using GPIOs for the ready/busy pin too. At a
> minimum, we need an updated DT binding doc for this, since I see you're
> adding this via device tree in a later patch (I don't see any DT binding
> patch for this; but I could just be overlooking it). It'd also be great
> if this support was moved to nand_dt_init() so other platforms can
> benefit, but I won't require that.
> 
> Also, previous [0] proposers had suggested 'rb-gpios', not 'ready-gpio'
> (the hardware docs typically call it 'rb' for ready/busy, FWIW). I don't
> really care, but the name should be going into a doc, so we can choose
> the same one everywhere.
> 
> EDIT: looks like the discussion was partly here [1] and it seems we're
> landing on "rb-gpios" in the latest version [2]. Can we stick with that?

Why should it be "rb-gpios" and not "rb-gpio"?
I don't think there are multiple gpios for r/b# function.

cheers,
-roger

> 
> Regards,
> Brian
> 
> [0] "Previous" may be subject to debate, as both series have been going
>     for several revisions.
> [1] http://patchwork.ozlabs.org/patch/515327/
> [2] http://patchwork.ozlabs.org/patch/526819/
> 
>> +	if (IS_ERR(info->ready_gpiod)) {
>> +		dev_err(dev, "failed to get ready gpio\n");
>> +		return PTR_ERR(info->ready_gpiod);
>> +	}
>> +
>>  	/*
>>  	 * If RDY/BSY line is connected to OMAP then use the omap ready
>>  	 * function and the generic nand_wait function which reads the status
>> @@ -1822,7 +1829,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>>  	 * chip delay which is slightly more than tR (AC Timing) of the NAND
>>  	 * device and read status register until you get a failure or success
>>  	 */
>> -	if (info->dev_ready) {
>> +	if (info->ready_gpiod) {
>>  		nand_chip->dev_ready = omap_dev_ready;
>>  		nand_chip->chip_delay = 0;
>>  	} else {
>> diff --git a/include/linux/platform_data/mtd-nand-omap2.h b/include/linux/platform_data/mtd-nand-omap2.h
>> index ff27e5a..19e509d 100644
>> --- a/include/linux/platform_data/mtd-nand-omap2.h
>> +++ b/include/linux/platform_data/mtd-nand-omap2.h
>> @@ -70,7 +70,6 @@ struct omap_nand_platform_data {
>>  	int			cs;
>>  	struct mtd_partition	*parts;
>>  	int			nr_parts;
>> -	bool			dev_ready;
>>  	bool			flash_bbt;
>>  	enum nand_io		xfer_type;
>>  	int			devsize;
>> @@ -81,5 +80,6 @@ struct omap_nand_platform_data {
>>  	/* deprecated */
>>  	struct gpmc_nand_regs	reg;
>>  	struct device_node	*of_node;
>> +	bool			dev_ready;
>>  };
>>  #endif
>> -- 
>> 2.1.4
>>