When 2 commands are submitted in a row, and the second is very quick,
the completion of the second command might never come. This happens
especially if the second command is quick, such as a status read after
an erase.
The issue is that in the interrupt handler, the status bits are cleared
after the new command is issued. There is a small temporal window where
this happens :
- the previous command has set the command done bit
- the ready for a command bit is set
- the handler submits the next command
- just then, the command completes, and the command done bit is still
set
- the handler clears the "previous" command done bit
- the handler exits
In this flow, the "command done" of the next command will never trigger
a new interrupt to finish the status command, as it was cleared for both
commands.
Fix this by clearing the status bit before submitting a new command.
Signed-off-by: Robert Jarzmik <robert.jarz...@free.fr>
---
drivers/mtd/nand/pxa3xx_nand.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index d1a4c336de1d..d6c696798811 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -675,8 +675,14 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
is_ready = 1;
}
+ /*
+ * Clear all status bit before issuing the next command, which
+ * can and will alter the status bits and will deserve a new
+ * interrupt on its own. This lets the controller exit the IRQ
+ */
+ nand_writel(info, NDSR, status);
+
if (status & NDSR_WRCMDREQ) {
- nand_writel(info, NDSR, NDSR_WRCMDREQ);
status &= ~NDSR_WRCMDREQ;
info->state = STATE_CMD_HANDLE;
@@ -697,8 +703,6 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
nand_writel(info, NDCB0, info->ndcb3);
}
- /* clear NDSR to let the controller exit the IRQ */
- nand_writel(info, NDSR, status);
if (is_completed)
complete(&info->cmd_complete);
if (is_ready)
--
2.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
