Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752749AbdLHLrm (ORCPT ); Fri, 8 Dec 2017 06:47:42 -0500 Received: from ozlabs.org ([103.22.144.67]:52887 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750878AbdLHLrk (ORCPT ); Fri, 8 Dec 2017 06:47:40 -0500 From: Michael Ellerman To: "Rafael J. Wysocki" , "Gautham R. Shenoy" Cc: Shilpasri G Bhat , Viresh Kumar , "Rafael J. Wysocki" , huntbag@linux.vnet.ibm.com, akshay.adiga@linux.vnet.ibm.com, Vaidyanathan Srinivasan , Linux PM , Linux Kernel Mailing List , linuxppc-dev , Stable Subject: Re: [v2 PATCH] cpufreq: powernv: Correctly parse the sign of pstates on POWER8 vs POWER9 In-Reply-To: References: <1512626365-22845-1-git-send-email-ego@linux.vnet.ibm.com> Date: Fri, 08 Dec 2017 22:47:38 +1100 Message-ID: <87indhh25h.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1486 Lines: 34 "Rafael J. Wysocki" writes: > On Thu, Dec 7, 2017 at 6:59 AM, Gautham R. Shenoy > wrote: >> From: "Gautham R. Shenoy" >> >> On POWERNV platform, Pstates are 8-bit values. On POWER8 they are >> negatively numbered while on POWER9 they are positively >> numbered. Thus, on POWER9, the maximum number of pstates could be as >> high as 256. >> >> The current code interprets pstates as a signed 8-bit value. This >> causes a problem on POWER9 platforms which have more than 128 pstates. >> On such systems, on a CPU that is in a lower pstate whose number is >> greater than 128, querying the current pstate returns a "pstate X is >> out of bound" error message and the current pstate is reported as the >> nominal pstate. >> >> This patch fixes the aforementioned issue by correctly differentiating >> the sign whenever a pstate value read, depending on whether the >> pstates are positively numbered or negatively numbered. >> >> Fixes: commit 09ca4c9b5958 ("cpufreq: powernv: Replacing pstate_id with frequency table index") >> Cc: #v4.8 >> Signed-off-by: Gautham R. Shenoy >> Tested-and-reviewed-by: Shilpasri G Bhat >> Acked-by: Viresh Kumar > > I'm going to apply this, or please let me know if you want to route it > differently. Do you mind waiting for now, we're still debating how to fix it. cheers