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mtd: nand: pxa3xx-nand: fix random command timeouts 

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.jarzmik@free.fr>
Acked-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
This commit is contained in:
Robert Jarzmik 2015-08-19 20:30:15 +02:00 committed by Brian Norris
parent 0b14392db2
commit 21fc0ef965
1 changed files with 7 additions and 3 deletions
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10
drivers/mtd/nand/pxa3xx_nand.c
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@ -678,8 +678,14 @@ 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;
@ -700,8 +706,6 @@ 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)