linux-kernel - Re: [PATCH 3/8] staging: et131x: Use for loop to initialise contiguous registers to zero

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Date:	Sun, 31 Aug 2014 15:25:03 +0100
From:	Mark Einon <mark.einon@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	devel@...verdev.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] staging: et131x: Use for loop to initialise
 contiguous registers to zero

On Sat, Aug 30, 2014 at 01:32:16PM -0700, Greg KH wrote:
> On Wed, Aug 20, 2014 at 11:17:53PM +0100, Mark Einon wrote:
> > Replace a long list of contiguous writel() calls with a for loop iterating
> > over the same values.
> > 
> > Signed-off-by: Mark Einon <mark.einon@...il.com>
> > ---
> >  drivers/staging/et131x/et131x.c | 27 +++------------------------
> >  1 file changed, 3 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/staging/et131x/et131x.c b/drivers/staging/et131x/et131x.c
> > index fffe763..44cc684 100644
> > --- a/drivers/staging/et131x/et131x.c
> > +++ b/drivers/staging/et131x/et131x.c
> > @@ -1138,6 +1138,7 @@ static void et1310_config_rxmac_regs(struct et131x_adapter *adapter)
> >  	u32 sa_lo;
> >  	u32 sa_hi = 0;
> >  	u32 pf_ctrl = 0;
> > +	u32 *wolw;
> >  
> >  	/* Disable the MAC while it is being configured (also disable WOL) */
> >  	writel(0x8, &rxmac->ctrl);
> > @@ -1151,30 +1152,8 @@ static void et1310_config_rxmac_regs(struct et131x_adapter *adapter)
> >  	 * its default Values of 0x00000000 because there are not WOL masks
> >  	 * as of this time.
> >  	 */
> > -	writel(0, &rxmac->mask0_word0);
> > -	writel(0, &rxmac->mask0_word1);
> > -	writel(0, &rxmac->mask0_word2);
> > -	writel(0, &rxmac->mask0_word3);
> > -
> > -	writel(0, &rxmac->mask1_word0);
> > -	writel(0, &rxmac->mask1_word1);
> > -	writel(0, &rxmac->mask1_word2);
> > -	writel(0, &rxmac->mask1_word3);
> > -
> > -	writel(0, &rxmac->mask2_word0);
> > -	writel(0, &rxmac->mask2_word1);
> > -	writel(0, &rxmac->mask2_word2);
> > -	writel(0, &rxmac->mask2_word3);
> > -
> > -	writel(0, &rxmac->mask3_word0);
> > -	writel(0, &rxmac->mask3_word1);
> > -	writel(0, &rxmac->mask3_word2);
> > -	writel(0, &rxmac->mask3_word3);
> > -
> > -	writel(0, &rxmac->mask4_word0);
> > -	writel(0, &rxmac->mask4_word1);
> > -	writel(0, &rxmac->mask4_word2);
> > -	writel(0, &rxmac->mask4_word3);
> > +	for (wolw = &rxmac->mask0_word0; wolw <= &rxmac->mask4_word3; wolw++)
> > +		writel(0, wolw);
> 
> You are now only writing to all locations 1 time, instead of 4 times,
> like before, are you sure that is ok?  Hardware is flaky, sometimes it
> wants to be written to multiple times...

Hi Greg,

Thanks for the review.

As far as my understanding goes, the new code is equivalent to the old
code - it's a little confusing that the name refers to a word, but the
masks are all 32 bit values, and the loop iterates over the contiguous
list of masks found in txmac_regs (et131x.h:891 - the masks are also
unused in the driver after being set).

Or am I missing something here?

Cheers,

Mark
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