From: "Jayachandran C." <jchandra@broadcom.com>
To: "David Daney" <ddaney.cavm@gmail.com>
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: Re: [PATCH 2/3] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT
Date: Wed, 20 Mar 2013 23:31:04 +0530 [thread overview]
Message-ID: <20130320180104.GA8100@jayachandranc.netlogicmicro.com> (raw)
In-Reply-To: <5149E7A4.3040906@gmail.com>
On Wed, Mar 20, 2013 at 09:45:24AM -0700, David Daney wrote:
> On 03/20/2013 09:27 AM, Jayachandran C wrote:
> >Allow usage of scratch register for current pgd even when
> >MIPS_PGD_C0_CONTEXT is not configured. MIPS_PGD_C0_CONTEXT is set
> >for 64r2 platforms to indicate availability of Xcontext for saving
> >cpuid, thus freeing Context which was used for cpuid to be used for
> >saving PGD. This option was also tied to using a scratch register for
> >storing PGD.
> >
> >This commit will allow usage of scratch register to store the current
> >pgd if one can be allocated for the platform, even when
> >MIPS_PGD_C0_CONTEXT is not set. The cpu id will be kept in the CP0
> >Context register in this case.
>
>
> The point of MIPS_PGD_C0_CONTEXT is really to indicate that the PGD
> pointer is stored in a register (or portion thereof) and that
> setting the PGD is done by calling into uasm generated code.
>
> Perhaps we should rename this Kconfig vairable so that its name
> indicates its function, or remove it altogether if possible, and
> machine generate the setting of the PGD pointer even when it is
> stored in the array in memory.
Removing the MIPS_PGD_C0_CONTEXT Kconfig variable does not look feasible.
The processor id is used by get_saved_sp macro and it needs to know at
compile time whether the processor id is in Context or Xcontext. We could
call it something like MIPS_PROCESSOR_ID_IN_XCONTEXT (if it would not
affect too many config files).
The second part (generating code for setting PGD pointer in pgd_current) is
already in the patch. This generated code also saves PGD to the scratch
register if one was allocated.
JC.
next prev parent reply other threads:[~2013-03-20 17:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-20 16:27 [PATCH v2 0/3] Use scratch registers on XLR/XLS/XLP Jayachandran C
2013-03-20 16:27 ` [PATCH 1/3] MIPS: Allow platform specific scratch registers Jayachandran C
2013-03-20 16:27 ` [PATCH 2/3] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT Jayachandran C
2013-03-20 16:45 ` David Daney
2013-03-20 18:01 ` Jayachandran C. [this message]
2013-03-20 16:27 ` [PATCH 3/3] MIPS: Move definition of SMP processor id register to header file Jayachandran C
-- strict thread matches above, loose matches on Subject: below --
2013-06-23 18:16 [PATCH 0/3] Use scratch registers when MIPS_PGD_C0_CONTEXT is not set Jayachandran C
2013-06-23 18:16 ` [PATCH 2/3] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT Jayachandran C
2013-01-08 12:56 [RFC PATCH 0/3] Use scratch registers on XLR/XLS/XLP Jayachandran C
2013-01-08 12:56 ` [PATCH 2/3] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT Jayachandran C
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