netdev - Re: [PATCH 1/2] net: sh_eth: use correct "struct device" when calling DMA mapping functions

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Date:   Tue, 5 Dec 2017 10:38:35 +0100
From:   Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "David S. Miller" <davem@...emloft.net>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms+renesas@...ge.net.au>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH 1/2] net: sh_eth: use correct "struct device" when
 calling DMA mapping functions

Hello,

On Tue, 5 Dec 2017 09:39:35 +0100, Geert Uytterhoeven wrote:

> >    Using 'ndev->dev.parent' (as in ravb) also should work... not sure which
> > is better  
> 
> That was going to be my comment, too. I also haven't checked which
> generates the smallest code.

Using ndev->dev.parent actually generates bigger code (44 bytes larger) :

$ size drivers/net/ethernet/renesas/sh_eth.o.*
   text	   data	    bss	    dec	    hex	filename
  27803	    696	      0	  28499	   6f53	drivers/net/ethernet/renesas/sh_eth.o.new
  27759	    696	      0	  28455	   6f27	drivers/net/ethernet/renesas/sh_eth.o.orig

.orig is my original proposal, .new is with ndev->dev.parent. I'm using
a gcc 6.4.0 compiler.

Note also that the driver is already using mdp->pdev->dev all over the place:

$ grep -- mdp-\>pdev-\>dev drivers/net/ethernet/renesas/sh_eth.c
		pm_wakeup_event(&mdp->pdev->dev, 0);
	pm_runtime_get_sync(&mdp->pdev->dev);
	pm_runtime_put_sync(&mdp->pdev->dev);
	device_set_wakeup_enable(&mdp->pdev->dev, mdp->wol_enabled);
	pm_runtime_get_sync(&mdp->pdev->dev);
	pm_runtime_put_sync(&mdp->pdev->dev);
	pm_runtime_put_sync(&mdp->pdev->dev);
	struct device *dev = &mdp->pdev->dev;

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com