Re: [PATCH] c_can: Add support for eg20t (pch_can)

[Alexander Stein <alexander.stein@systec-electronic.com>]

On Tuesday 08 April 2014 10:26:23, Thomas Gleixner wrote:
> > So I noticed that with CONFIG_CAN_C_CAN_STRICT_FRAME_ORDERING=n
> > (NEWDAT and INTPEND cleared immediately) the "odd behavior" occurs
> > pretty often.
> > Before
> >   c_can_rx_object_get(dev, obj);
> > NEWDAT is still set, but afterwards it is already cleared in
> > C_CAN_NEWDAT1_REG.
> 
> Which is expected. We clear the newdat bit in c_can_rx_object_get(),
> which updates C_CAN_NEWDAT1_REG as well.
> 
> > I guess the NEWDAT is already cleared in the message object before
> > reading from the message object with this line
> 
> > > ctrl = priv->read_reg(priv, C_CAN_IFACE(MSGCTRL_REG, IF_RX));
> > 
> > So I removed that IF_MCONT_NEWDAT check (see below) and I didn't
> > lose any message, but get 5 duplicates in 250000 messages (no
> > reordering though).
> > 
> > Setting CONFIG_CAN_C_CAN_STRICT_FRAME_ORDERING=y with that patch I
> > lose ~650msg per 250000 frames.
> 
> What happens, if you apply the patch below?
> 
> Thanks,
> 
> 	tglx
> 
> Index: linux-2.6/drivers/net/can/c_can/c_can.c
> ===================================================================
> --- linux-2.6.orig/drivers/net/can/c_can/c_can.c
> +++ linux-2.6/drivers/net/can/c_can/c_can.c
> @@ -880,7 +880,7 @@ static int c_can_do_rx_poll(struct net_d
>  
>  	while (quota > 0) {
>  		if (!pend) {
> -			pend = priv->read_reg(priv, C_CAN_INTPND1_REG);
> +			pend = priv->read_reg(priv, C_CAN_NEWDAT1_REG);
>  			if (!pend)
>  				break;
>  			/*

Your patch "can: c_can: Get rid of pointless interrupts" already did that change. Or did you mean the reverse?

Regards,
Alexander
-- 
Dipl.-Inf. Alexander Stein

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