linux-kernel - Re: [PATCH v10 3/5] CPM/QE: use genalloc to manage CPM/QE muram

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Date:	Tue, 22 Sep 2015 23:02:58 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Zhao Qiang-B45475 <qiang.zhao@...escale.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"lauraa@...eaurora.org" <lauraa@...eaurora.org>,
	Xie Xiaobo-R63061 <X.Xie@...escale.com>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	Li Yang-Leo-R58472 <LeoLi@...escale.com>,
	"paulus@...ba.org" <paulus@...ba.org>
Subject: Re: [PATCH v10 3/5] CPM/QE: use genalloc to manage CPM/QE muram

On Tue, 2015-09-22 at 21:20 -0500, Zhao Qiang-B45475 wrote:
> On Wen, Sep 23, 2015 at 8:19 AM +0800, Wood Scott-B07421 wrote:
> 
> > > > >  {
> > > > > - int ret;
> > > > > +
> > > > > + unsigned long start;
> > > > >   unsigned long flags;
> > > > > + unsigned long size_alloc = size; struct muram_block *entry; int
> > > > > + end_bit; int order = muram_pool->min_alloc_order;
> > > > > 
> > > > >   spin_lock_irqsave(&cpm_muram_lock, flags);
> > > > > - ret = rh_free(&cpm_muram_info, offset);
> > > > > + end_bit = (offset >> order) + ((size + (1UL << order) - 1) >>
> > > > order);
> > > > > + if ((offset + size) > (end_bit << order))
> > > > > +         size_alloc = size + (1UL << order);
> > > > 
> > > > Why do you need to do all these calculations here?
> > > 
> > > So do it in gen_pool_fixed_alloc?
> > 
> > Could you explain why they're needed at all?
> 
> Why it does the calculations? 
> If the min block of gen_pool is 8 bytes, and I want to allocate a 
> Region with offset=7, size=8bytes, I actually need block 0 and block 1,
> And the allocation will give me block 0.  

How can you have offset 7 if the minimum order is 2 bytes?

-Scott

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