Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751733AbbKINXd (ORCPT ); Mon, 9 Nov 2015 08:23:33 -0500 Received: from eusmtp01.atmel.com ([212.144.249.243]:25098 "EHLO eusmtp01.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751149AbbKINXb (ORCPT ); Mon, 9 Nov 2015 08:23:31 -0500 Date: Mon, 9 Nov 2015 14:23:05 +0100 From: Ludovic Desroches To: , , CC: , , , , , , Ludovic Desroches Subject: Re: [PATCH 1/2] mmc: sdhci: set bus voltage before enabling bus power Message-ID: <20151109132305.GC15706@odux.rfo.atmel.com> Mail-Followup-To: ulf.hansson@linaro.org, nicolas.ferre@atmel.com, alexandre.belloni@free-electrons.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, plagnioj@jcrosoft.com, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, pierre.samat@atmel.com References: <1446825570-30029-1-git-send-email-ludovic.desroches@atmel.com> <1446825570-30029-2-git-send-email-ludovic.desroches@atmel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1446825570-30029-2-git-send-email-ludovic.desroches@atmel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2062 Lines: 58 On Fri, Nov 06, 2015 at 04:59:29PM +0100, Ludovic Desroches wrote: > When there is a vmmc regulator, only SD Bus Power is set to 1 in the > Power Control Register. It means SD Bus Voltage Select field is set to 0 > that is a reserved value. The SD Host Controller specification says: > 'SD Bus Power: Before setting this bit, the SD Host Driver shall set SD > Bus Voltage Select.' and 'If the Host Driver selects an unsupported > voltage in the SD B?us Voltage Select field, the Host Controller may > ignore writes to SD Bus Power and keep its value at zero." > > Having an external regulator means the SD Bus Voltage Select is useless > but if the Host Controller strictly follows the specification then we > need to set a valid value. Ulf, What is your opinion about this patch? If the 'no regulator found' message is turned in debug message, I can get rid of my vmmc regulator but I really think that writing only SDHCI_POWER_ON is opposite to the sdhci spec. I would say that not setting the bus voltage is a quirk! Regards Ludovic > > Signed-off-by: Ludovic Desroches > --- > drivers/mmc/host/sdhci.c | 7 ------- > 1 file changed, 7 deletions(-) > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c > index ac97b46..0cfd7b2 100644 > --- a/drivers/mmc/host/sdhci.c > +++ b/drivers/mmc/host/sdhci.c > @@ -1278,13 +1278,6 @@ static void sdhci_set_power(struct sdhci_host *host, unsigned char mode, > spin_unlock_irq(&host->lock); > mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, vdd); > spin_lock_irq(&host->lock); > - > - if (mode != MMC_POWER_OFF) > - sdhci_writeb(host, SDHCI_POWER_ON, SDHCI_POWER_CONTROL); > - else > - sdhci_writeb(host, 0, SDHCI_POWER_CONTROL); > - > - return; > } > > if (mode != MMC_POWER_OFF) { > -- > 2.5.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/