Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752826AbdLGUVt (ORCPT ); Thu, 7 Dec 2017 15:21:49 -0500 Received: from mail-lf0-f67.google.com ([209.85.215.67]:37353 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973AbdLGUVq (ORCPT ); Thu, 7 Dec 2017 15:21:46 -0500 X-Google-Smtp-Source: AGs4zMbYacFg02jXak+AxF+If+BY059ldsQl3KH8Be8MCYbnwudGCFH2ABGJmaj6BKwtZo3l4x1e+A== Date: Thu, 7 Dec 2017 22:21:41 +0200 From: Ivan Khoronzhuk To: David Miller Cc: grygorii.strashko@ti.com, netdev@vger.kernel.org, linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] net: ethernet: ti: cpdma: rate is not changed - correct case Message-ID: <20171207202140.GD3022@khorivan> Mail-Followup-To: David Miller , grygorii.strashko@ti.com, netdev@vger.kernel.org, linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org References: <20171207194855.GA3022@khorivan> <20171207.145024.1434883857028947517.davem@davemloft.net> <20171207201005.GC3022@khorivan> <20171207.151315.1535972470633975595.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171207.151315.1535972470633975595.davem@davemloft.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2459 Lines: 57 On Thu, Dec 07, 2017 at 03:13:15PM -0500, David Miller wrote: > From: Ivan Khoronzhuk > Date: Thu, 7 Dec 2017 22:10:06 +0200 > > > On Thu, Dec 07, 2017 at 02:50:24PM -0500, David Miller wrote: > >> From: Ivan Khoronzhuk > >> Date: Thu, 7 Dec 2017 21:48:56 +0200 > >> > >> > On Wed, Dec 06, 2017 at 04:35:45PM -0500, David Miller wrote: > >> >> From: Ivan Khoronzhuk > >> >> Date: Wed, 6 Dec 2017 16:41:18 +0200 > >> >> > >> >> > If rate is the same as set it's correct case. > >> >> > > >> >> > Signed-off-by: Ivan Khoronzhuk > >> >> > --- > >> >> > Based on net-next/master > >> >> > > >> >> > drivers/net/ethernet/ti/davinci_cpdma.c | 2 +- > >> >> > 1 file changed, 1 insertion(+), 1 deletion(-) > >> >> > > >> >> > diff --git a/drivers/net/ethernet/ti/davinci_cpdma.c b/drivers/net/ethernet/ti/davinci_cpdma.c > >> >> > index e4d6edf..dbe9167 100644 > >> >> > --- a/drivers/net/ethernet/ti/davinci_cpdma.c > >> >> > +++ b/drivers/net/ethernet/ti/davinci_cpdma.c > >> >> > @@ -841,7 +841,7 @@ int cpdma_chan_set_rate(struct cpdma_chan *ch, u32 rate) > >> >> > return -EINVAL; > >> >> > > >> >> > if (ch->rate == rate) > >> >> > - return rate; > >> >> > + return 0; > >> >> > >> >> Looking at the one and only caller of this function, cpsw_ndo_set_tx_maxrate, it > >> >> makes sure this can never, ever, happen. > >> > In current circumstances yes, it will never happen. > >> > But I caught it while adding related code and better return 0 if upper caller > >> > doesn't have such check. Suppose that cpdma module is responsible for itself > >> > and if it's critical I can send this patch along with whole related series. > >> > >> You have to decide one way or the other, who is responsible. > >> > >> I think checking higher up is better because it's cheaper at that point to > >> look at the per-netdev queue rate setting before moving down deeper into the > >> driver specific data-structures. > > > > No objection, but upper caller not always knows current rate and for doing like > > this it needs read it first, and this is also some redundancy. > > How can the upper caller not know the current rate? The rate is > always stored in the generic netdev per-queue datastructure. > > And that's what existing code checks right now. Right now, when generic netdev only caller - yes. -- Regards, Ivan Khoronzhuk