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

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Message-ID: <87k2zha69p.fsf@free.fr>
Date:	Mon, 16 Feb 2015 22:36:02 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	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>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.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

Maxime Ripard <maxime.ripard@...e-electrons.com> writes:

>> I don't think an mdelay(256) is acceptable.
>
> That's very true that this driver would need some love, but
> valentine's day was last week.
That doesn't cope with the 256ms mdelay. And a potential big mdelay is not what
I'd call a bug fix, see below.

> I'm sorry, but this is a patch targeted for stable. This is a pure
> bugfix. I won't rewrite the whole driver solely to make the driver
> better, especially since that would make such a patch (or more likely
> a whole serie) unsuitable for stable.

This is the rewrite I was asking for (not tested), consider it against your
"rewrite the whole driver" :

	Modified   drivers/mtd/nand/pxa3xx_nand.c
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;

--
Robert

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