linux-kernel - Re: [PATCH] soc: fsl/qe: fix Oops on CPM1 (and likely CPM2)

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Date:	Fri, 12 Aug 2016 08:25:30 +0200
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Scott Wood <oss@...error.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Zhao Qiang <qiang.zhao@....com>,
	"David S.Miller" <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] soc: fsl/qe: fix Oops on CPM1 (and likely CPM2)



Le 12/08/2016 à 01:29, Scott Wood a écrit :
> On Mon, 2016-08-08 at 18:08 +0200, Christophe Leroy wrote:
>> Commit 0e6e01ff694ee ("CPM/QE: use genalloc to manage CPM/QE muram")
>> has changed the way muram is managed.
>> genalloc uses kmalloc(), hence requires the SLAB to be up and running.
>>
>> On powerpc 8xx, cpm_reset() is called early during startup.
>> cpm_reset() then calls cpm_muram_init() before SLAB is available,
>> hence the following Oops.
>>
>> cpm_reset() cannot be called during initcalls because the CPM is
>> needed for console
>>
>> This patch splits cpm_muram_init() in two parts. The first part,
>> related to mappings, is kept as cpm_muram_init()
>> The second part is named cpm_muram_pool_init() and is called
>> the first time cpm_muram_alloc() is used
>
> Why do you need to split it, versus calling the full cpm_muram_init() on
> demand?
>

There are drivers like for instance de i2c-cpm driver, that for instance 
call cpm_muram_addr() before calling cpm_muram_alloc()
Therefore, we need muram_vbase and muram_pbase set.

So if we want to keep a single function, it means we also have to call 
it on demand from cpm_muram_addr(), cpm_muram_offset() and cpm_muram_dma().

Is that what you recommend ?

Christophe