netdev - Re: [PATCH 1/2] ravb: stop reading ECMR in ravb_emac

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Date:	Mon, 11 Jan 2016 14:11:25 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [PATCH 1/2] ravb: stop reading ECMR in ravb_emac_init()

Hello.

On 1/11/2016 12:45 PM, Geert Uytterhoeven wrote:

> On Sun, Jan 10, 2016 at 10:27 PM, Sergei Shtylyov
> <sergei.shtylyov@...entembedded.com> wrote:
>> The code in ravb_emac_init() twiddling the ECMR bits always looked a bit
>> strange to me: if one intends to respect 'priv->duplex', why save old value
>> of the ECMR.DM bit?   As all the other bits are zeroed anyway, we don't
>> really need to read ECMR before writing to it.
>
> Just an observation, I don't know about correctness: priv->duplex wasn't
> respected if ECMR_DM was already set before.
>
> Same comment for the second patch.

    That's what the patches try to fix. Perhaps the description was too terse?

>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
>>
>> ---
>>   drivers/net/ethernet/renesas/ravb_main.c |    7 ++-----
>>   1 file changed, 2 insertions(+), 5 deletions(-)
>>
>> Index: net/drivers/net/ethernet/renesas/ravb_main.c
>> ===================================================================
>> --- net.orig/drivers/net/ethernet/renesas/ravb_main.c
>> +++ net/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -338,16 +338,13 @@ error:
>>   static void ravb_emac_init(struct net_device *ndev)
>>   {
>>          struct ravb_private *priv = netdev_priv(ndev);
>> -       u32 ecmr;
>>
>>          /* Receive frame limit set register */
>>          ravb_write(ndev, ndev->mtu + ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN, RFLR);
>>
>>          /* PAUSE prohibition */
>> -       ecmr =  ravb_read(ndev, ECMR);
>> -       ecmr &= ECMR_DM;
>
> Perhaps you misread as "ecmr &= ~ECMR_DM"?

    If it was so, there would be no point in patching...

[...]

> Gr{oetje,eeting}s,
>
>                          Geert

MBR, Sergei