Re: RFC: [PATCH v2 1/2] can: flexcan: Correctly initialize mailboxes

[David Jander <david@protonic.nl>]

On Tue,  2 Sep 2014 17:03:35 +0200
Marc Kleine-Budde <mkl@pengutronix.de> wrote:

> From: David Jander <david@protonic.nl>
> 
> Apparently mailboxes may contain random data at startup, causing some of
> them being prepared for message reception. This causes overruns being
> missed or even confusing the IRQ check for trasmitted messages, increasing
> the transmit counter instead of the error counter.
> 
> Signed-off-by: David Jander <david@protonic.nl>
> [mkl: adjust starting value of loop]
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
> Changes since v1:
> - don't remove existing initialization of FLEXCAN_TX_BUF_ID
> - start loop at FLEXCAN_TX_BUF_ID + 1
> 
> Marc
> 
>  drivers/net/can/flexcan.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index 630c7bf..6ec49bd 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -801,6 +801,7 @@ static int flexcan_chip_start(struct net_device *dev)
>  	struct flexcan_regs __iomem *regs = priv->base;
>  	int err;
>  	u32 reg_mcr, reg_ctrl;
> +	int i;
>  
>  	/* enable module */
>  	err = flexcan_chip_enable(priv);
> @@ -870,6 +871,11 @@ static int flexcan_chip_start(struct net_device *dev)
>  	/* Abort any pending TX, mark Mailbox as INACTIVE */
>  	flexcan_write(FLEXCAN_MB_CNT_CODE(0x4),
>  		      &regs->cantxfg[FLEXCAN_TX_BUF_ID].can_ctrl);
> +	/* Clear and invalidate all mailboxes first */
> +	for (i = FLEXCAN_TX_BUF_ID + 1; i < ARRAY_SIZE(regs->cantxfg; i++) {
> +		flexcan_write(FLEXCAN_MB_CNT_CODE(0),
> +		      &regs->cantxfg[i].can_ctrl);
> +	}
>  
>  	/* acceptance mask/acceptance code (accept everything) */
>  	flexcan_write(0x0, &regs->rxgmask);

This assumes that FLEXCAN_TX_BUF_ID is the ID of the first available MB. Other
than that, it should work I believe.
OTOH, since this loop is more like a memset(...0...), wouldn't it be nice to
just clear all MB's CODE registers and then initialize TX_BUF (and others)
afterwards?

Best regards,

-- 
David Jander
Protonic Holland.