From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932352Ab0JUQHs (ORCPT ); Thu, 21 Oct 2010 12:07:48 -0400 Received: from [69.28.251.93] ([69.28.251.93]:59951 "EHLO b32.net" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751160Ab0JUQHr (ORCPT ); Thu, 21 Oct 2010 12:07:47 -0400 From: Kevin Cernekee Subject: [PATCH v3 8/9] MIPS: Honor L2 bypass bit To: Ralf Baechle Cc: , Date: Thu, 21 Oct 2010 08:59:48 -0700 Message-Id: <2e65c61bf8fd3a7b2aa4e24013cb0dba@localhost> User-Agent: vim 7.2 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [v3: Fix build errors] On many of the newer MIPS32 cores, CP0 CONFIG2 bit 12 (L2B) indicates that the L2 cache is disabled and therefore Linux should not attempt to use it. Signed-off-by: Ralf Baechle Signed-off-by: Kevin Cernekee Cc: linux-mips@linux-mips.org> Cc: --- arch/mips/mm/sc-mips.c | 38 ++++++++++++++++++++++++++++++++++---- 1 files changed, 34 insertions(+), 4 deletions(-) diff --git a/arch/mips/mm/sc-mips.c b/arch/mips/mm/sc-mips.c index 5ab5fa8..ef625eb 100644 --- a/arch/mips/mm/sc-mips.c +++ b/arch/mips/mm/sc-mips.c @@ -57,6 +57,38 @@ static struct bcache_ops mips_sc_ops = { .bc_inv = mips_sc_inv }; +/* + * Check if the L2 cache controller is activated on a particular platform. + * MTI's L2 controller and the L2 cache controller of Broadcom's BMIPS + * cores both use c0_config2's bit 12 as "L2 Bypass" bit, that is the + * cache being disabled. However there is no guarantee for this to be + * true on all platforms. In an act of stupidity the spec defined bits + * 12..15 as implementation defined so below function will eventually have + * to be replaced by a platform specific probe. + */ +static inline int mips_sc_is_activated(struct cpuinfo_mips *c, + unsigned int config2) +{ + unsigned int tmp; + + /* Check the bypass bit (L2B) */ + switch (c->cputype) { + case CPU_34K: + case CPU_74K: + case CPU_1004K: + case CPU_BMIPS5000: + if (config2 & (1 << 12)) + return 0; + } + + tmp = (config2 >> 4) & 0x0f; + if (0 < tmp && tmp <= 7) + c->scache.linesz = 2 << tmp; + else + return 0; + return 1; +} + static inline int __init mips_sc_probe(void) { struct cpuinfo_mips *c = ¤t_cpu_data; @@ -79,10 +111,8 @@ static inline int __init mips_sc_probe(void) return 0; config2 = read_c0_config2(); - tmp = (config2 >> 4) & 0x0f; - if (0 < tmp && tmp <= 7) - c->scache.linesz = 2 << tmp; - else + + if (!mips_sc_is_activated(c, config2)) return 0; tmp = (config2 >> 8) & 0x0f; -- 1.7.0.4