[v2,4/9] mtd: nand: atmel: Avoid ECC errors when leaving backup mode

Message ID 20170915140411.31716-5-romain.izard.pro@gmail.com
State New
Headers show
Series
  • Various patches for SAMA5D2 backup mode
Related show

Commit Message

Romain Izard Sept. 15, 2017, 2:04 p.m.
During backup mode, the contents of all registers will be cleared as the
SoC will be completely powered down. For a product that boots on NAND
Flash memory, the bootloader will obviously use the related controller
to read the Flash and correct any detected error in the memory, before
handling back control to the kernel's resuming entry point.

In normal devices, it is up to the driver's suspend/resume code to
restore the registers in a valid state. But the PMECC is not a regular
device in the driver model when used with the legacy device tree binding
for the Atmel NAND controller, and suspend/resume code is not called.

As in my case the bootloader leaves the PMECC controller in a programmed
state, and the controller is only reset at boot or after a NAND access,
the first NAND Flash access with the Atmel controller will report
uncorrectable ECC errors.

To avoid this, systematically reset the PMECC controller before using
it.

Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
---
 drivers/mtd/nand/atmel/pmecc.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

Comments

Boris Brezillon Sept. 18, 2017, 9:50 a.m. | #1
Hi Romain,

On Fri, 15 Sep 2017 16:04:06 +0200
Romain Izard <romain.izard.pro@gmail.com> wrote:

> During backup mode, the contents of all registers will be cleared as the
> SoC will be completely powered down. For a product that boots on NAND
> Flash memory, the bootloader will obviously use the related controller
> to read the Flash and correct any detected error in the memory, before
> handling back control to the kernel's resuming entry point.
> 
> In normal devices, it is up to the driver's suspend/resume code to
> restore the registers in a valid state. But the PMECC is not a regular
> device in the driver model when used with the legacy device tree binding
> for the Atmel NAND controller, and suspend/resume code is not called.
> 
> As in my case the bootloader leaves the PMECC controller in a programmed
> state, and the controller is only reset at boot or after a NAND access,
> the first NAND Flash access with the Atmel controller will report
> uncorrectable ECC errors.
> 
> To avoid this, systematically reset the PMECC controller before using
> it.
> 
> Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
> ---
>  drivers/mtd/nand/atmel/pmecc.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mtd/nand/atmel/pmecc.c b/drivers/mtd/nand/atmel/pmecc.c
> index 8c210a5776bc..8d1208f38025 100644
> --- a/drivers/mtd/nand/atmel/pmecc.c
> +++ b/drivers/mtd/nand/atmel/pmecc.c
> @@ -777,6 +777,9 @@ int atmel_pmecc_enable(struct atmel_pmecc_user *user, int op)
>  
>  	mutex_lock(&user->pmecc->lock);
>  
> +	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
> +	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
> +
>  	cfg = user->cache.cfg;
>  	if (op == NAND_ECC_WRITE)
>  		cfg |= PMECC_CFG_WRITE_OP;
> @@ -797,10 +800,6 @@ EXPORT_SYMBOL_GPL(atmel_pmecc_enable);
>  
>  void atmel_pmecc_disable(struct atmel_pmecc_user *user)
>  {
> -	struct atmel_pmecc *pmecc = user->pmecc;
> -
> -	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
> -	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);

So know you leave the ECC engine enabled even when it's not in use? Not
sure what kind of implication this has on power-consumption, but I
think I'd prefer to keep the write RST+DISABLE sequence in the disable
path.

How about creating a atmel_pmecc_reset() function that you'd call from
the nand-controller resume hook. Something like:

void atmel_pmecc_reset(struct atmel_pmecc *pmecc)
{
	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
}

This way you can re-use the same function and call it from the probe
and disable path as well.

Regards,

Boris

>  	mutex_unlock(&user->pmecc->lock);
>  }
>  EXPORT_SYMBOL_GPL(atmel_pmecc_disable);
> @@ -856,10 +855,6 @@ static struct atmel_pmecc *atmel_pmecc_create(struct platform_device *pdev,
>  	/* Disable all interrupts before registering the PMECC handler. */
>  	writel(0xffffffff, pmecc->regs.base + ATMEL_PMECC_IDR);
>  
> -	/* Reset the ECC engine */
> -	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
> -	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
> -
>  	return pmecc;
>  }
>  

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Patch

diff --git a/drivers/mtd/nand/atmel/pmecc.c b/drivers/mtd/nand/atmel/pmecc.c
index 8c210a5776bc..8d1208f38025 100644
--- a/drivers/mtd/nand/atmel/pmecc.c
+++ b/drivers/mtd/nand/atmel/pmecc.c
@@ -777,6 +777,9 @@  int atmel_pmecc_enable(struct atmel_pmecc_user *user, int op)
 
 	mutex_lock(&user->pmecc->lock);
 
+	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
+	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
+
 	cfg = user->cache.cfg;
 	if (op == NAND_ECC_WRITE)
 		cfg |= PMECC_CFG_WRITE_OP;
@@ -797,10 +800,6 @@  EXPORT_SYMBOL_GPL(atmel_pmecc_enable);
 
 void atmel_pmecc_disable(struct atmel_pmecc_user *user)
 {
-	struct atmel_pmecc *pmecc = user->pmecc;
-
-	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
-	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
 	mutex_unlock(&user->pmecc->lock);
 }
 EXPORT_SYMBOL_GPL(atmel_pmecc_disable);
@@ -856,10 +855,6 @@  static struct atmel_pmecc *atmel_pmecc_create(struct platform_device *pdev,
 	/* Disable all interrupts before registering the PMECC handler. */
 	writel(0xffffffff, pmecc->regs.base + ATMEL_PMECC_IDR);
 
-	/* Reset the ECC engine */
-	writel(PMECC_CTRL_RST, pmecc->regs.base + ATMEL_PMECC_CTRL);
-	writel(PMECC_CTRL_DISABLE, pmecc->regs.base + ATMEL_PMECC_CTRL);
-
 	return pmecc;
 }