From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161240AbcFMJEL (ORCPT ); Mon, 13 Jun 2016 05:04:11 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:46686 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161137AbcFMJEJ (ORCPT ); Mon, 13 Jun 2016 05:04:09 -0400 Subject: Re: [PATCH] gpio: pca953x: Fix NBANK calculation for PCA9536 To: Linus Walleij References: <20160609053204.32398-1-vigneshr@ti.com> CC: Alexandre Courbot , "linux-gpio@vger.kernel.org" , "linux-kernel@vger.kernel.org" From: Vignesh R Message-ID: <575E7704.5090503@ti.com> Date: Mon, 13 Jun 2016 14:34:04 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 13 June 2016 12:52 PM, Linus Walleij wrote: > On Thu, Jun 9, 2016 at 7:32 AM, Vignesh R wrote: > >> NBANK() macro assumes that ngpios is a multiple of 8(BANK_SZ) and >> hence results in 0 banks for PCA9536 which has just 4 gpios. This is >> wrong as PCA9356 has 1 bank with 4 gpios. This results in uninitialized >> PCA953X_INVERT register. Fix this by using DIV_ROUND_UP macro in >> NBANK(). >> >> Cc: stable@vger.kernel.org >> Signed-off-by: Vignesh R > > Patch applied. > > Is this really a regression or affecting systems in development? > > Which machine/device tree makes this problematic? > I observed this on am335x-icev2 evm which is system in development. Basically, variable with uninitialized value (junk) gets written to PCA953X_INVERT register(in device_pca953x_init()) causing driver to report wrong gpio pin status. So, this bug will affect any platform with PCA9536 chip. Quick grep on arch/*/boot/dts/ folder shows one platform already using pca9536 chip. Hence, I added Cc to stable kernel. -- Regards Vignesh