Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754589AbaKKL7N (ORCPT ); Tue, 11 Nov 2014 06:59:13 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:57315 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753701AbaKKLJn (ORCPT ); Tue, 11 Nov 2014 06:09:43 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Dirk Brandewie , "Rafael J. Wysocki" , Luis Henriques Subject: [PATCH 3.16.y-ckt 046/170] intel_pstate: Correct BYT VID values. Date: Tue, 11 Nov 2014 11:06:45 +0000 Message-Id: <1415704129-12709-47-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1415704129-12709-1-git-send-email-luis.henriques@canonical.com> References: <1415704129-12709-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Dirk Brandewie commit d022a65ed2473fac4a600e3424503dc571160a3e upstream. Using a VID value that is not high enough for the requested P state can cause machine checks. Add a ceiling function to ensure calulated VIDs with fractional values are set to the next highest integer VID value. The algorythm for calculating the non-trubo VID from the BIOS writers guide is: vid_ratio = (vid_max - vid_min) / (max_pstate - min_pstate) vid = ceiling(vid_min + (req_pstate - min_pstate) * vid_ratio) Signed-off-by: Dirk Brandewie Signed-off-by: Rafael J. Wysocki Signed-off-by: Luis Henriques --- drivers/cpufreq/intel_pstate.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 72c90a1ebb5f..4598b8731b55 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -53,6 +53,17 @@ static inline int32_t div_fp(int32_t x, int32_t y) return div_s64((int64_t)x << FRAC_BITS, (int64_t)y); } +static inline int ceiling_fp(int32_t x) +{ + int mask, ret; + + ret = fp_toint(x); + mask = (1 << FRAC_BITS) - 1; + if (x & mask) + ret += 1; + return ret; +} + struct sample { int32_t core_pct_busy; u64 aperf; @@ -424,7 +435,7 @@ static void byt_set_pstate(struct cpudata *cpudata, int pstate) cpudata->vid.ratio); vid_fp = clamp_t(int32_t, vid_fp, cpudata->vid.min, cpudata->vid.max); - vid = fp_toint(vid_fp); + vid = ceiling_fp(vid_fp); if (pstate > cpudata->pstate.max_pstate) vid = cpudata->vid.turbo; -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/