From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B64CC433F5 for ; Fri, 4 Mar 2022 21:12:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229550AbiCDVMw (ORCPT ); Fri, 4 Mar 2022 16:12:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229464AbiCDVMu (ORCPT ); Fri, 4 Mar 2022 16:12:50 -0500 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDE0838BC2 for ; Fri, 4 Mar 2022 13:12:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646428321; x=1677964321; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=ykWgWP/GD+9Jm+IbipK2/JYt9vytoc4D+hbYU5DMUts=; b=BHr+YwXpuqNZhFBZJhrSWd94weN1x8LqMRtZgctOQKHM07CVOLIygvF8 DX2l4usEU/93e4OH2TRgG3u+pVIUmgqlb3DaUVfKJ1G0YMPhX2SeXi/Y+ hsKVqVABE6gPaumqj8JW1wlMkSmfHYO2hW8F+QSATHw4xft706RDIsMTi TOHfdLYC2cGtPaL7PMoojWs+fl57XIW/q38qwFKweAZ8bI+H09wwBwvtN YMtleo4r118Gm+kRZt1iFX2e3iHJ1K6SsJq22tHBZiTDlQW9i6nyO6qQx z6Nii6PaTEHosXuLsi7++NEprX6tNR6O5yEqEEs1jRdBP3bdeBkEYjRp3 w==; X-IronPort-AV: E=McAfee;i="6200,9189,10276"; a="278757374" X-IronPort-AV: E=Sophos;i="5.90,156,1643702400"; d="scan'208";a="278757374" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2022 13:12:01 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,156,1643702400"; d="scan'208";a="552369587" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.151]) by orsmga008.jf.intel.com with SMTP; 04 Mar 2022 13:11:54 -0800 Received: by stinkbox (sSMTP sendmail emulation); Fri, 04 Mar 2022 23:11:54 +0200 Date: Fri, 4 Mar 2022 23:11:54 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: trix@redhat.com Cc: jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, tvrtko.ursulin@linux.intel.com, airlied@linux.ie, daniel@ffwll.ch, nathan@kernel.org, ndesaulniers@google.com, matthew.d.roper@intel.com, lucas.demarchi@intel.com, airlied@redhat.com, imre.deak@intel.com, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH] drm/i915: rework the error handling in *_dpll_params Message-ID: References: <20220304210355.608898-1-trix@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220304210355.608898-1-trix@redhat.com> X-Patchwork-Hint: comment Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 04, 2022 at 01:03:55PM -0800, trix@redhat.com wrote: > From: Tom Rix > > Clang static analysis reports this issue > intel_dpll.c:472:31: warning: The left operand of '-' > is a garbage value [core.UndefinedBinaryOperatorResult] > this_err = abs(clock.dot - target); > ~~~~~~~~~ ^ > > In a loop clock.dot is set on successful call to > i9xx_calc_dpll_params(). If the call fails, the later > *is_valid() will use the previous loop's clock.dot. I don't think this can happen. intel_pll_is_valid() validates all the dividers first and bails out if they are junk. > > The *_dpll_params functions return an arithmetic statement > with the clock.dot as the variable. Change the error handler > to set clock.dot to 0 and jump to the return statement. > > Fixes: dccbea3b0704 ("drm/i915: calculate the port clock rate along with other PLL params") > Signed-off-by: Tom Rix > --- > drivers/gpu/drm/i915/display/intel_dpll.c | 32 ++++++++++++++--------- > 1 file changed, 20 insertions(+), 12 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_dpll.c b/drivers/gpu/drm/i915/display/intel_dpll.c > index 0ae37fdbf2a5b..ba7cada704288 100644 > --- a/drivers/gpu/drm/i915/display/intel_dpll.c > +++ b/drivers/gpu/drm/i915/display/intel_dpll.c > @@ -309,11 +309,13 @@ int pnv_calc_dpll_params(int refclk, struct dpll *clock) > { > clock->m = clock->m2 + 2; > clock->p = clock->p1 * clock->p2; > - if (WARN_ON(clock->n == 0 || clock->p == 0)) > - return 0; > + if (WARN_ON(clock->n == 0 || clock->p == 0)) { > + clock->dot = 0; > + goto end; > + } > clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n); > clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p); > - > +end: > return clock->dot; > } > > @@ -326,11 +328,13 @@ int i9xx_calc_dpll_params(int refclk, struct dpll *clock) > { > clock->m = i9xx_dpll_compute_m(clock); > clock->p = clock->p1 * clock->p2; > - if (WARN_ON(clock->n + 2 == 0 || clock->p == 0)) > - return 0; > + if (WARN_ON(clock->n + 2 == 0 || clock->p == 0)) { > + clock->dot = 0; > + goto end; > + } > clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n + 2); > clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p); > - > +end: > return clock->dot; > } > > @@ -338,11 +342,13 @@ int vlv_calc_dpll_params(int refclk, struct dpll *clock) > { > clock->m = clock->m1 * clock->m2; > clock->p = clock->p1 * clock->p2; > - if (WARN_ON(clock->n == 0 || clock->p == 0)) > - return 0; > + if (WARN_ON(clock->n == 0 || clock->p == 0)) { > + clock->dot = 0; > + goto end; > + } > clock->vco = DIV_ROUND_CLOSEST(refclk * clock->m, clock->n); > clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p); > - > +end: > return clock->dot / 5; > } > > @@ -350,12 +356,14 @@ int chv_calc_dpll_params(int refclk, struct dpll *clock) > { > clock->m = clock->m1 * clock->m2; > clock->p = clock->p1 * clock->p2; > - if (WARN_ON(clock->n == 0 || clock->p == 0)) > - return 0; > + if (WARN_ON(clock->n == 0 || clock->p == 0)) { > + clock->dot = 0; > + goto end; > + } > clock->vco = DIV_ROUND_CLOSEST_ULL(mul_u32_u32(refclk, clock->m), > clock->n << 22); > clock->dot = DIV_ROUND_CLOSEST(clock->vco, clock->p); > - > +end: > return clock->dot / 5; > } > > -- > 2.26.3 -- Ville Syrjälä Intel