Hi Robert,

On Mon, Feb 16, 2015 at 09:11:24PM +0100, Robert Jarzmik wrote:

Maxime Ripard [off-list ref] writes:

quoted

 drivers/mtd/nand/pxa3xx_nand.c | 47 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index 96b0b1d27df1..b2d8d6960765 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c

@@ -480,6 +480,41 @@ static void disable_int(struct pxa3xx_nand_info *info, uint32_t int_mask)
 	nand_writel(info, NDCR, ndcr | int_mask);
 }
 
+static void drain_fifo(struct pxa3xx_nand_info *info, void *data, int len)
+{
+	if (info->ecc_bch) {
+		int index = 0;
+
+		while (index < (len * 4)) {
+			u32 timeout;
+
+			__raw_readsl(info->mmio_base + NDDB, data + index, 8);
+
+			/*
+			 * According to the datasheet, when reading
+			 * from NDDB with BCH enabled, after each 32
+			 * bytes reads, we have to make sure that the
+			 * NDSR.RDDREQ bit is set
+			 */
+			for (timeout = 0;
+			     !(nand_readl(info, NDSR) & NDSR_RDDREQ);
+			     timeout++) {
+				if (timeout >= 5) {
+					dev_err(&info->pdev->dev,
+						"Timeout on RDDREQ while draining the FIFO\n");
+					return;
+				}
+
+				mdelay(1);

So in worst case, we'll end up with 4 times mdelay(1) times len / 32.
For a 2048 page, it is : 256ms where everything is stuck (mdelay and not
msleep).

I know you had no choice because this is called from interrupt handler (top
half). But having a irq handler and a irq thread handler would solve that issue,
and you'll end up with msleep(1) in this code.

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.

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.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com