From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
To: figo zhang <figo1802@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
David Daney <ddaney@caviumnetworks.com>,
macro@linux-mips.org, linux-mips@linux-mips.org
Subject: Re: Dma addr should use Kuseg1 for MIPS32?
Date: Tue, 08 Dec 2009 14:36:58 +0300 [thread overview]
Message-ID: <4B1E3A5A.9050100@ru.mvista.com> (raw)
In-Reply-To: <c6ed1ac50912071749m49b1e5f5m7ae53384389338d9@mail.gmail.com>
Hello.
figo zhang wrote:
>
> > i write dma_phy to DMA base register, but why it cannot work? it
> should
> > write Kseg1 space to DMA register?
> > I remember that it is ok for ARM/X86 .
>
> It's only happens to work on some systems.
>
>
> in my puzzle, if i run
> dma_vaddr =(char*) __get_free_pages(GFP_KERNEL, order);
> dma_phy = virt_to_phy(dma_vaddr);
>
> if the result is:
> dma_vaddr = 0x801b00000;
> dma_phy = 0x1b00000;
>
> so i should write 0x1b00000 to my DMA Base register or wirte
> (0x1b000000 | 0xa0000000) to DMA?
You must always use the physical addresses when programming DMA, i.e.
0x1b00000 in this case.
WBR, Sergei
next prev parent reply other threads:[~2009-12-08 11:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-07 12:55 Dma addr should use Kuseg1 for MIPS32? figo zhang
2009-12-07 13:45 ` Ralf Baechle
2009-12-08 1:49 ` figo zhang
2009-12-08 11:36 ` Sergei Shtylyov [this message]
2009-12-09 11:46 ` figo zhang
2009-12-09 11:47 ` figo zhang
[not found] <c6ed1ac50912062352u227c28e1me2107dbf7bd8a0ea@mail.gmail.com>
2009-12-07 13:30 ` zhangfx
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