From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E07F253AD for ; Mon, 17 Jul 2023 14:53:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689605582; x=1721141582; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=PaYQUrnIAw10UGRh51Er0CiQIbO+1qEOK90eqGzlL3M=; b=ktI/SBeSGFeViZ21yY4vkJ1kAny1rLi50XAeE5FPZ9vhc3IQXNmo4xWL VWvHGSuNbns2VWNoParX1QHMV+PjTcOFy7+Nano3GOCKHJmx38NX78Vzr 5yrjxvCqX1Me5dNXLOGyvnNyXnNx2iLTa3Pt9dduFGS+evA/HLAZj57UF 7ngtF4jo1jX1k0l3NYZBENUmdXHsmNT0pjOKmsDfd0Rg5wLY4Yc4kfRxm Fp59pyYH5UWmp/hbglycrIeVeGJLgUwFN+xF+VeEy3lgHTlhbLIoS/UTS 6U/H7Y63aWjMFDVgYk4GC5lHdiQUdM4Passq61Ftb2joVkMWQr77cwRcz A==; X-IronPort-AV: E=McAfee;i="6600,9927,10774"; a="432120114" X-IronPort-AV: E=Sophos;i="6.01,211,1684825200"; d="scan'208";a="432120114" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jul 2023 07:53:01 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10774"; a="788686219" X-IronPort-AV: E=Sophos;i="6.01,211,1684825200"; d="scan'208";a="788686219" Received: from ahajda-mobl.ger.corp.intel.com (HELO [10.213.9.23]) ([10.213.9.23]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jul 2023 07:52:55 -0700 Message-ID: <0cae35ea-7635-383d-cae5-2051abbc6d64@intel.com> Date: Mon, 17 Jul 2023 16:52:51 +0200 Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.13.0 Subject: Re: [PATCH] drm/i915/tv: avoid possible division by zero To: Su Hui , jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, tvrtko.ursulin@linux.intel.com, airlied@gmail.com, daniel@ffwll.ch, nathan@kernel.org, ndesaulniers@google.com, trix@redhat.com Cc: ville.syrjala@linux.intel.com, mripard@kernel.org, ankit.k.nautiyal@intel.com, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, kernel-janitors@vger.kernel.org References: <20230717062209.124106-1-suhui@nfschina.com> Content-Language: en-US From: Andrzej Hajda Organization: Intel Technology Poland sp. z o.o. - ul. Slowackiego 173, 80-298 Gdansk - KRS 101882 - NIP 957-07-52-316 In-Reply-To: <20230717062209.124106-1-suhui@nfschina.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 17.07.2023 08:22, Su Hui wrote: > Clang warning: drivers/gpu/drm/i915/display/intel_tv.c: > line 991, column 22 Division by zero. > Assuming tv_mode->oversample=1 and (!tv_mode->progressive)=1, > then division by zero will happen. > > Fixes: 1bba5543e4fe ("drm/i915: Fix TV encoder clock computation") > Signed-off-by: Su Hui > --- > drivers/gpu/drm/i915/display/intel_tv.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_tv.c b/drivers/gpu/drm/i915/display/intel_tv.c > index 36b479b46b60..82b54af51f23 100644 > --- a/drivers/gpu/drm/i915/display/intel_tv.c > +++ b/drivers/gpu/drm/i915/display/intel_tv.c > @@ -988,7 +988,8 @@ intel_tv_mode_to_mode(struct drm_display_mode *mode, > const struct tv_mode *tv_mode, > int clock) > { > - mode->clock = clock / (tv_mode->oversample >> !tv_mode->progressive); > + mode->clock = clock / (tv_mode->oversample != 1 ? > + tv_mode->oversample >> !tv_mode->progressive : 1); Seems too smart to me, why not just: mode->clock = clock / tv_mode->oversample; if (!tv_mode->progressive)     mode->clock <<= 1; Or trying being smart: mode->clock = clock / tv_mode->oversample << !tv_mode->progressive; Btw in both cases there is assumption tv_mode->oversample != 0, I guess it is true. Regards Andrzej > > /* > * tv_mode horizontal timings: