From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752203AbdAMP5m (ORCPT <rfc822;w@1wt.eu>);
        Fri, 13 Jan 2017 10:57:42 -0500
Received: from mx07-00178001.pphosted.com ([62.209.51.94]:48854 "EHLO
        mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S1752022AbdAMP5k (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 13 Jan 2017 10:57:40 -0500
Subject: Re: [PATCH 3/3] rtc: stm32: use 32-bit cast for BIT() macro
To: Arnd Bergmann <arnd@arndb.de>,
        Alexandre Belloni <alexandre.belloni@free-electrons.com>
References: <20170113153311.2611510-1-arnd@arndb.de>
 <20170113153311.2611510-3-arnd@arndb.de>
CC: Mark Brown <broonie@kernel.org>,
        Alessandro Zummo <a.zummo@towertech.it>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre TORGUE <alexandre.torgue@st.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        "rtc-linux@googlegroups.com" <rtc-linux@googlegroups.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
From: Amelie DELAUNAY <amelie.delaunay@st.com>
Message-ID: <26624cbe-7e71-35a4-b8df-f5ac5d15b1ec@st.com>
Date: Fri, 13 Jan 2017 16:56:54 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.5.1
MIME-Version: 1.0
In-Reply-To: <20170113153311.2611510-3-arnd@arndb.de>
Content-Type: text/plain; charset="windows-1252"; format=flowed
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.75.127.47]
X-ClientProxiedBy: SFHDAG3NODE3.st.com (10.75.127.9) To SFHDAG3NODE2.st.com
 (10.75.127.8)
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-13_09:,,
 signatures=0
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Arnd,

On 01/13/2017 04:32 PM, Arnd Bergmann wrote:
> Using the ~ operator on a BIT() constant results in a large 'unsigned long'
> constant that won't fit into an 'unsigned int' function argument on 64-bit
> architectures, resulting in a harmless build warning in x86 allmodconfig:
>
> drivers/rtc/rtc-stm32.c: In function 'stm32_rtc_probe':
> drivers/rtc/rtc-stm32.c:651:51: error: large integer implicitly truncated to unsigned type [-Werror=overflow]
>   regmap_update_bits(rtc->dbp, PWR_CR, PWR_CR_DBP, ~PWR_CR_DBP);
I thought I would fix this warning by replacing all ~PWR_CR_DBP by 0, 
because the mask PWR_CR_DBP prevents other bits to be cleared.
In this way, I avoid the ugly cast...
>
> This works around the warning by adding an explict cast to 'u32', but
> that is unfortunately a bit ugly and I feel there should be a better
> way to do this, possibly with some changes to either the bitops.h
> header or the regmap API.
>
> Cc: Mark Brown <broonie@kernel.org>
> Fixes: 4e64350f42e2 ("rtc: add STM32 RTC driver")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/rtc/rtc-stm32.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/rtc/rtc-stm32.c b/drivers/rtc/rtc-stm32.c
> index 8c599f52124c..05d3dc89e55f 100644
> --- a/drivers/rtc/rtc-stm32.c
> +++ b/drivers/rtc/rtc-stm32.c
> @@ -92,7 +92,7 @@
>  /* STM32_PWR_CR */
>  #define PWR_CR				0x00
>  /* STM32_PWR_CR bit field */
> -#define PWR_CR_DBP			BIT(8)
> +#define PWR_CR_DBP			(u32)BIT(8)
>
>  struct stm32_rtc {
>  	struct rtc_device *rtc_dev;
>

Regards,
Amelie