linux-kernel - Re: [PATCH 2/2] adm8211: fix the possible pci cache line sizes inside switch-case

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Message-ID: <20150506063241.GA3042@bytefire-computer>
Date:	Wed, 6 May 2015 07:32:42 +0100
From:	Okash Khawaja <okash.khawaja@...il.com>
To:	Kalle Valo <kvalo@...eaurora.org>
Cc:	joe@...ches.com, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] adm8211: fix the possible pci cache line sizes
 inside switch-case

On Wed, May 06, 2015 at 07:59:04AM +0300, Kalle Valo wrote:
> Okash Khawaja <okash.khawaja@...il.com> writes:
> 
> > The PCI cache line size value was being compared against decimal values prefixed with 0x.
> >
> > Fixed the literals to use the correct hex values.
> >
> >
> > Signed-off-by: Okash Khawaja <okash.khawaja@...il.com>
> 
> [...]
> 
> > @@ -1101,10 +1101,10 @@ static void adm8211_hw_init(struct ieee80211_hw *dev)
> >  		case  0x8:
> >  			reg |= (0x1 << 14);
> >  			break;
> > -		case 0x16:
> > +		case 0x10:
> >  			reg |= (0x2 << 14);
> >  			break;
> > -		case 0x32:
> > +		case 0x20:
> >  			reg |= (0x3 << 14);
> >  			break;
> >  		default:
> 
> Did you test this? How certain can we be that this doesn't break
> anything?
> 

I didn't test it as that would require the hardware that I don't have at the moment. However, the value in `cline` is PCI cache line size, which is the CPU's cache line size. It is less likely for cache line sizes to be 22 or 50, and more likely for them to be 16 or 32. Also, as far as I understand (and I might be wrong here), cache line size is used for things like aligning DMA requests with CPU cache line, which improve performance but wouldn't break anything if the value doesn't match. In this case, we will fall through to the default case which leaves `reg` unchanged.

If there is a way to test it with a mock set up or if you still think we need to test this on real board, I'll be happy to try get the hardware. But I will need some guidance around that. Thanks.

> -- 
> Kalle Valo
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