From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ulf Hansson Subject: Re: [PATCH] mmc:sdio:retry CMD52/53 when error happens Date: Tue, 15 May 2012 09:15:42 +0200 Message-ID: <4FB2029E.3060107@stericsson.com> References: <1336984792-13956-1-git-send-email-yongd@marvell.com> <4FB10156.2080900@stericsson.com> <89813612683626448B837EE5A0B6A7CB1A2B9F19B7@SC-VEXCH4.marvell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <89813612683626448B837EE5A0B6A7CB1A2B9F19B7@SC-VEXCH4.marvell.com> Sender: linux-kernel-owner@vger.kernel.org To: Yong Ding Cc: "cjb@laptop.org" , "linux-mmc@vger.kernel.org" , "stefan.xk.nilsson@stericsson.com" , "linus.walleij@linaro.org" , "svenkatr@ti.com" , "linux-kernel@vger.kernel.org" List-Id: linux-mmc@vger.kernel.org Hi Yong Ding, On 05/15/2012 05:14 AM, Yong Ding wrote: > Hi Ulf Hansson, Thanks for your comments. > > Such retry mechanism is a simple CMD-level or sdio-core-level retry > which takes advantage of the mmc core internal retry. There is not > any side effect, but with it, even those SDIO function driver's > without its own retrying mechanism can benefit in some conditions. I am not sure about that. It all depends on what kind of protocol the SDIO func driver is handling and as well what SDIO hw that is connected. For a WLAN interface you might end up in reading/writing the next buffer, maybe messing up even more data. Have you considered this? > > Besides, for CMD52, it can be used during SDIO card > initialization/detection phase. At that time, SDIO function driver > hasn't started to work. Of course we can probably encounter CMD52 > error due to some reasons(eg, board-level schematic bad behavior), > and such retry can be a potential workaround. Actually, we've > encountered exactly such case in our development. I realize that there is a need for this, but I am not sure we always would like to have "retries" for every CMD52/53 request. During SDIO initialization before SDIO func driver is started, retries should be safe since there is no upper protocol to consider yet. Maybe we should try to create a patch which only enables retries during SDIO init sequence instead!? Kind regards Ulf Hansson