Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751927AbdHaQbl (ORCPT ); Thu, 31 Aug 2017 12:31:41 -0400 Received: from smtprelay.synopsys.com ([198.182.60.111]:35634 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751672AbdHaQbk (ORCPT ); Thu, 31 Aug 2017 12:31:40 -0400 Subject: Re: [PATCH] arc: Flush and invalidate caches on start To: Alexey Brodkin , "linux-snps-arc@lists.infradead.org" CC: "linux-kernel@vger.kernel.org" References: <20170831142158.27245-1-abrodkin@synopsys.com> From: Vineet Gupta Message-ID: <7a5267e3-c012-7bfd-ced2-cfaa3f47524a@synopsys.com> Date: Thu, 31 Aug 2017 09:31:33 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170831142158.27245-1-abrodkin@synopsys.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.10.161.108] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1414 Lines: 49 On 08/31/2017 07:22 AM, Alexey Brodkin wrote: > This is useful to make sure no stale data exists in caches after bootloaders. > The worst thing could be some lines of cache were locked in a bootloader > for example during DDR recalibration and never unlocked. This may lead > to really unpredictable issues later down the line. > > Signed-off-by: Alexey Brodkin > --- > arch/arc/kernel/head.S | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S > index 8b90d25a15cc..04e28b664183 100644 > --- a/arch/arc/kernel/head.S > +++ b/arch/arc/kernel/head.S > @@ -34,6 +34,10 @@ > #endif > sr r5, [ARC_REG_IC_CTRL] > > + ; Invalidate entire I$ > + mov r5, 1 > + sr r5, [ARC_REG_IC_IVIC] > + > 1: > lr r5, [ARC_REG_DC_BCR] > breq r5, 0, 1f ; D$ doesn't exist > @@ -46,6 +50,18 @@ > #endif > sr r5, [ARC_REG_DC_CTRL] > > + ; Flush entire D$ > + mov r5, 1 > + sr r5, [ARC_REG_DC_FLSH] > + ; Wait for flush operation to complete > +1: > + lr r5, [ARC_REG_DC_CTRL] > + bbit1 r5, DC_CTRL_FLUSH_STATUS, 1b > + > + ; Invalidate entire D$ > + mov r5, 1 > + sr r5, [ARC_REG_DC_IVDC] > + AFAIK uboot already flushes the caches before handing control over to kernel - so why do we need it here. If uboot is locking lines, it needs to fix that and not penalize the general case with or w/o uboot ! -Vineet