From: Ralf Baechle <ralf@linux-mips.org>
To: "Steven J. Hill" <Steven.Hill@imgtec.com>,
Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Subject: Re: [PATCH 05/11] MIPS: mm: c-r4k: Ensure CCA is set to non-coherent on UP kernels.
Date: Thu, 13 Nov 2014 11:31:08 +0100 [thread overview]
Message-ID: <20141113103108.GB13753@linux-mips.org> (raw)
In-Reply-To: <1415858743-24492-6-git-send-email-Steven.Hill@imgtec.com>
On Thu, Nov 13, 2014 at 12:05:37AM -0600, Steven J. Hill wrote:
> diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
> index 1559360..076e660 100644
> --- a/arch/mips/mm/c-r4k.c
> +++ b/arch/mips/mm/c-r4k.c
> @@ -1595,8 +1595,17 @@ early_param("cca", cca_setup);
>
> static void coherency_setup(void)
> {
> - if (cca < 0 || cca > 7)
> - cca = read_c0_config() & CONF_CM_CMASK;
> + if (cca < 0 || cca > 7) {
> + /*
> + * Set CCA to non-coherent to ensure that the UP kernel
> + * behaves properly even on MC processors where the ROM
> + * may have prepared the C0 registers for SMP operation.
> + */
> + if (!config_enabled(CONFIG_SMP))
> + cca = _CACHE_CACHABLE_NONCOHERENT >> _CACHE_SHIFT;
> + else
> + cca = read_c0_config() & CONF_CM_CMASK;
> + }
NAK. This would trigger falsely on pretty much every SMP platform in
MIPS history except Octeon - with usually fatal consequences.
Is there a performance disadvantage or why is this desirable?
Ralf
next prev parent reply other threads:[~2014-11-13 10:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-13 6:05 [PATCH 00/11] Add support for eXtended Physical Addressing Steven J. Hill
2014-11-13 6:05 ` [PATCH 01/11] MIPS: HIGHMEM fixes for cache aliasing and non-DMA I/O Steven J. Hill
2014-11-13 6:05 ` [PATCH 02/11] MIPS: Revert fixrange_init() limiting to the FIXMAP region Steven J. Hill
2014-11-13 11:13 ` Ralf Baechle
2014-11-13 6:05 ` [PATCH 03/11] MIPS: Rearrange PTE bits into fixed positions for MIPS R2 Steven J. Hill
2014-11-13 6:05 ` [PATCH 04/11] MIPS: Removal of execute bit in page tables for HEAP/BSS Steven J. Hill
2014-11-13 11:36 ` Ralf Baechle
2014-11-13 6:05 ` [PATCH 05/11] MIPS: mm: c-r4k: Ensure CCA is set to non-coherent on UP kernels Steven J. Hill
2014-11-13 10:31 ` Ralf Baechle [this message]
2014-11-13 6:05 ` [PATCH 06/11] MIPS: Add CP0 macros for extended EntryLo registers Steven J. Hill
2014-11-13 12:25 ` Sergei Shtylyov
2014-11-13 6:05 ` [PATCH 07/11] MIPS: Fix address type used for early memory detection Steven J. Hill
2014-11-13 6:05 ` [PATCH 08/11] MIPS: Cosmetic cleanups of page table headers Steven J. Hill
2014-11-13 6:05 ` [PATCH 09/11] MIPS: Add MFHC0 and MTHC0 instructions to uasm Steven J. Hill
2014-11-13 6:05 ` [PATCH 10/11] MIPS: Add support for XPA Steven J. Hill
2014-11-13 6:05 ` [PATCH 11/11] MIPS: XPA: Add new configuration file Steven J. Hill
2014-11-13 6:21 ` [PATCH 00/11] Add support for eXtended Physical Addressing Ralf Baechle
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