From: Palmer Dabbelt <palmer@sifive.com>
To: guoren@kernel.org
Cc: linux-arch@vger.kernel.org, aou@eecs.berkeley.edu,
linux-kernel@vger.kernel.org, mao_han@c-sky.com,
Christoph Hellwig <hch@infradead.org>,
ren_guo@c-sky.com, linux-riscv@lists.infradead.org
Subject: Re: [PATCH] riscv: fixup max_low_pfn with PFN_DOWN.
Date: Wed, 23 Jan 2019 18:00:35 -0800 (PST) [thread overview]
Message-ID: <mhng-7c486840-63d3-4645-84ff-8c89660fc552@palmer-si-x1c4> (raw)
In-Reply-To: <20190116010738.GA4817@guoren-Inspiron-7460>
On Tue, 15 Jan 2019 17:07:38 PST (-0800), guoren@kernel.org wrote:
> Hi Christoph,
>
> I use PFN_DOWN() every where as possible and seems it's a habit
> problem. So let risc-v maintainer to choose "PFN_DOW()" or
> ">> PAGE_SHIFT".
>
> Also the same with "end_of_DRAM & max_low_pfn".
PFN_DOWN makes sense to me, as that's what we're trying to do here (round a
physical address down to page frame number). Am a I misunderstanding
something?
>
> Best Regards
> Guo Ren
>
> On Tue, Jan 15, 2019 at 08:12:54AM -0800, Christoph Hellwig wrote:
>> On Wed, Jan 16, 2019 at 12:10:00AM +0800, Guo Ren wrote:
>> > > > set_max_mapnr(PFN_DOWN(mem_size));
>> > > > - max_low_pfn = memblock_end_of_DRAM();
>> > > > + max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
>> > >
>> > > I know it is used just above, but can we please just switch this
>> > > code to use >> PAGE_SHIFT instead of PFN_DOWN, which just horribly
>> > > obsfucates what is going on?
>> > ???
>> > #define PFN_DOWN(x) ((x) >> PAGE_SHIFT)
>> >
>> > phys_addr_t __init_memblock memblock_end_of_DRAM(void)
>> > {
>> > int idx = memblock.memory.cnt - 1;
>> >
>> > return (memblock.memory.regions[idx].base + memblock.memory.regions[idx].size);
>> > }
>> >
>> > What's the problem? PFN_DOWN() couldn't be used with function call?
>>
>> PFN_DOWN gives you the correct result. But I think it actually
>> drastically reduces readability over just opencoding it.
>>
>> > My patch just want to point out that max_low_pfn is PFN not size. In fact
>> > there is no error for running without my patch :P
>>
>> No, I think your patch is correct. I just wonder if we could make
>> the code easier to read.
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next prev parent reply other threads:[~2019-01-24 2:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-12 8:16 [PATCH] riscv: fixup max_low_pfn with PFN_DOWN guoren
2019-01-15 15:36 ` Christoph Hellwig
2019-01-15 16:10 ` Guo Ren
2019-01-15 16:12 ` Christoph Hellwig
2019-01-16 1:07 ` Guo Ren
2019-01-24 2:00 ` Palmer Dabbelt [this message]
2019-01-24 2:31 ` Guo Ren
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