linux-kernel - Re: [PATCH v3 1/2] mtd: nand: pxa3xx: Fix PIO FIFO draining

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Message-ID: <54E3777B.20607@free-electrons.com>
Date:	Tue, 17 Feb 2015 14:16:43 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:	Gregory Clement <gregory.clement@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Brian Norris <computersforpeace@...il.com>,
	Lior Amsalem <alior@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Thomas Petazzoni <thomas@...e-electrons.com>,
	Seif Mazareeb <seif@...vell.com>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org,
	Sudhakar Gundubogula <sudhakar@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Boris Brezillon <boris@...e-electrons.com>,
	linux-mtd@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] mtd: nand: pxa3xx: Fix PIO FIFO draining

On 02/17/2015 02:07 PM, Robert Jarzmik wrote:
> Maxime Ripard <maxime.ripard@...e-electrons.com> writes:
> 
>> On Mon, Feb 16, 2015 at 10:36:02PM +0100, Robert Jarzmik wrote:
>>> diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
>>> index e512902..6e569e9 100644
>>> --- a/drivers/mtd/nand/pxa3xx_nand.c
>>> +++ b/drivers/mtd/nand/pxa3xx_nand.c
>>> @@ -576,11 +576,20 @@ static void start_data_dma(struct pxa3xx_nand_info *info)
>>>  {}
>>>  #endif
>>>  
>>> +static irqreturn_t pxa3xx_nand_irq_thread(int irq, void *data)
>>> +{
>>> +	struct pxa3xx_nand_info *info = data;
>>> +
>>> +	handle_data_pio(info);
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>>  static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
>>>  {
>>>  	struct pxa3xx_nand_info *info = devid;
>>>  	unsigned int status, is_completed = 0, is_ready = 0;
>>>  	unsigned int ready, cmd_done;
>>> +	irqreturn_t ret = IRQ_HANDLED;
>>>  
>>>  	if (info->cs == 0) {
>>>  		ready           = NDSR_FLASH_RDY;
>>> @@ -622,7 +631,7 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
>>>  		} else {
>>>  			info->state = (status & NDSR_RDDREQ) ?
>>>  				      STATE_PIO_READING : STATE_PIO_WRITING;
>>> -			handle_data_pio(info);
>>> +			ret = IRQ_WAKE_THREAD;
>>>  		}
>>>  	}
>>>  	if (status & cmd_done) {
>>> @@ -663,7 +672,7 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
>>>  	if (is_ready)
>>>  		complete(&info->dev_ready);
>>>  NORMAL_IRQ_EXIT:
>>> -	return IRQ_HANDLED;
>>> +	return ret;
>>>  }
>>>  
>>>  static inline int is_buf_blank(uint8_t *buf, size_t len)
>>> @@ -1688,7 +1697,8 @@ static int alloc_nand_resource(struct platform_device *pdev)
>>>  	/* initialize all interrupts to be disabled */
>>>  	disable_int(info, NDSR_MASK);
>>>  
>>> -	ret = request_irq(irq, pxa3xx_nand_irq, 0, pdev->name, info);
>>> +	ret = request_threaded_irq(irq, pxa3xx_nand_irq,
>>> +				   pxa3xx_nand_irq_thread, 0, pdev->name, info);
>>>  	if (ret < 0) {
>>>  		dev_err(&pdev->dev, "failed to request IRQ\n");
>>>  		goto fail_free_buf;
>>
>> I just gave this patch a try, and it blows up quite badly:
>> http://code.bulix.org/p96krc-87889?raw
> Confirmed.
> OTOH, replacing :
>>> +			ret = IRQ_WAKE_THREAD;
> With:
> +			ret = IRQ_WAKE_THREAD;
> +			goto NORMAL_IRQ_EXIT;
> 
> is fully working in my environment, now I got 10mn to test it.
> I also added for cosmetics in pxa3xx_nand_irq_thread() a :
> 	info->state = STATE_CMD_DONE;
> 
>> It looks like there's more work here, most likely in the waitqueues
>> wake up.
> Not that much if I'm right, hein ?
> And it enables the msleep() instead of mdelay().
> 
> And the flow of the driver is not changed for pxa3xx, only for Armada (ie. non
> dma case) for which you need to introduce a delay anyway, and therefore change
> the flow.
> 
> It will be Brian choice eventually, but if you say that you will submit that
> approach for next cycle, and yours for stable, and that for next you'll convert
> mdelay() to msleep(), I'll stop arguing.
> 

How about you push a proper patchset with this alternative (and a nice
cover letter explaining the need for a threaded irq) so we can discuss
properly this new turn?

-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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