[U-Boot] [PATCH v3 2/2] net: fec_mxc: Poll FEC_TBD_READY after polling TDAR

[Marek Vasut]

On Thursday, August 21, 2014 at 06:12:09 PM, Fabio Estevam wrote:
> When testing the FEC driver on a mx6solox we noticed that the TDAR bit gets
> always cleared prior then the READY bit is set in the last BD, which causes
> FEC transmission to fail.
> 
> As explained by Ye Li:
> 
> "The TDAR bit is set when the descriptors are all out from TX ring, but the
> descriptor properly is in transmitting not READY. These are two signals,
> and in Ic simulation, we found the TDAR always clear prior than the READY
> bit of last BD. In mx6solox, we use a latest version of FEC IP. It looks
> the intrinsic behave of TDAR bit is changed in this FEC version, not any
> bug in mx6sx."
> 
> Fix this by polling the READY bit of BD after the TDAR polling, which
> covers the mx6solox case and does not harm for the other SoCs.
> 
> Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>
> ---
> Changes since v2:
> - Poll FEC_TBD_READY after polling TDAR
> 
>  drivers/net/fec_mxc.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c
> index 56178d4..3050e58 100644
> --- a/drivers/net/fec_mxc.c
> +++ b/drivers/net/fec_mxc.c
> @@ -719,12 +719,22 @@ static int fec_send(struct eth_device *dev, void
> *packet, int length) break;
>  	}
> 
> +	if (!timeout) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	timeout = FEC_XFER_TIMEOUT;
> +	while (--timeout) {
> +		if (!(readw(&fec->tbd_base[fec->tbd_index].status) & 
FEC_TBD_READY))

This will never work, because you never invalidate the memory over the DMA 
descriptor here.

> +			break;
> +	}
> +
>  	if (!timeout)
>  		ret = -EINVAL;
> 
> +out:
>  	invalidate_dcache_range(addr, addr + size);

And here you invalidate it for no reason ;-)

> -	if (readw(&fec->tbd_base[fec->tbd_index].status) & FEC_TBD_READY)
> -		ret = -EINVAL;
> 
>  	debug("fec_send: status 0x%x index %d ret %i\n",
>  			readw(&fec->tbd_base[fec->tbd_index].status),

Best regards,
Marek Vasut