From: Magnus Damm <damm@opensource.se>
To: Rupesh S <rupeshs@myw.ltindia.com>
Cc: linuxppc-embedded@lists.linuxppc.org
Subject: Re: Why not kmalloc() ??
Date: Fri, 16 Jul 2004 13:34:42 +0200 [thread overview]
Message-ID: <1089977681.27006.90.camel@kubu.opensource.se> (raw)
In-Reply-To: <s0f7edc2.025@EMAIL>
On Fri, 2004-07-16 at 11:25, Rupesh S wrote:
> Hi,
>
> I just figured out that I need to use m8xx_cpm_hostalloc() to allocate memory for "buffer" that needs to be attached to the "Buffer Descriptor" of an MPC8xx CPM peripheral (like IIC, SPI, SCC etc). Instead, if I try to use kmalloc() or a static memory allocation, my driver isn't working.
>
> 1) Can somebody throw some light on what exactly is the difference between m8xx_cpm_hostalloc() and kmalloc().
kmalloc allocates from the kernel memory pool, ie your sdram.
you usually have several megabytes of sdram.
hostalloc allocates memory from the internal dpram area in the mpc8xx
processor. a mpc8xx-processor usually has around 4-8 kilobyte dpram.
> 2) Why is the difference important in ppc linux ?
the dpram (dual port ram) is used to communicate with the cpm devices
such as scc:s and smc.s found inside processors from the mpc8xx family.
the powerpc core has access to one side, the cpm has access to the other
side of the dual port memory. sort of anyway.
consult your friendly mpc8xx manual for further info.
/magnus
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2004-07-16 11:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-16 9:25 Why not kmalloc() ?? Rupesh S
2004-07-16 10:25 ` kernel 2.4.26 doesn't seem to work with a MPC859T Pedro Aguilar
2004-07-16 11:34 ` Magnus Damm [this message]
2004-07-16 12:06 ` Why not kmalloc() ?? sanjeev ramachandran
2004-07-16 13:32 ` Dan Malek
2004-07-16 14:06 ` Mark Chambers
2004-07-16 15:42 ` Rune Torgersen
2004-07-16 19:03 ` Dan Malek
2004-07-16 19:02 ` Dan Malek
2004-07-16 13:29 ` Dan Malek
2004-07-16 11:46 ` Dan Malek
-- strict thread matches above, loose matches on Subject: below --
2004-07-17 4:51 Rupesh S
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