Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756276AbcKBQqJ (ORCPT ); Wed, 2 Nov 2016 12:46:09 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:41116 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756025AbcKBQqI (ORCPT ); Wed, 2 Nov 2016 12:46:08 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Wed, 02 Nov 2016 09:40:02 -0700 From: Stefan Agner To: Dong Aisheng Cc: "Leonardo G. Veiga" , Ulf Hansson , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, raul.munoz@toradex.com, leonardo.veiga@toradex.com, Haibo Chen Subject: Re: [PATCH] sdhci-esdhc-imx: fix bus-width for 1-bit operation. In-Reply-To: References: <1478015905-31262-1-git-send-email-leogveiga@gmail.com> Message-ID: User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2739 Lines: 73 On 2016-11-02 01:42, Dong Aisheng wrote: > Hi Leonardo, > > On Tue, Nov 1, 2016 at 11:58 PM, Leonardo G. Veiga wrote: >> From: Leonardo Graboski Veiga >> >> The 1-bit operation mode, enabled by seeting the 'bus-width' property of >> the device tree 'esdhc' node to <1>, not work while using SD card. >> >> The behavior is only noticed when only the data pin 0 is connected to the >> hardware. A series of kernel errors are printed to the console, all of them >> returning the following error message followed by some explanation: >> mmcblk0: error -84 transferring data >> >> If four data lines are connected, it ignores the device-tree >> property and works in 4-bit mode of operation without errors. The hardware >> used for testing does not support 8-bit mode. >> >> Check the 'bus-width' property and if set to <1>, enable the >> SDHCI_QUIRK_FORCE_1_BIT_DATA quirk. >> >> Signed-off-by: Leonardo Graboski Veiga >> --- >> drivers/mmc/host/sdhci-esdhc-imx.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c >> index c9fbc4c3..88d7d22 100644 >> --- a/drivers/mmc/host/sdhci-esdhc-imx.c >> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c >> @@ -1003,6 +1003,10 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev, >> host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V; >> } >> >> + if (!of_property_read_u32(np, "bus-width", &boarddata->max_bus_width) >> + && boarddata->max_bus_width == 1) >> + host->quirks |= SDHCI_QUIRK_FORCE_1_BIT_DATA; >> + > > This looks like a common SDHCI driver issue that it assumes the default > bus-width as 4 bit if no SDHCI_QUIRK_FORCE_1_BIT_DATA specified. > if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA)) > mmc->caps |= MMC_CAP_4_BIT_DATA; > > And I'm not sure Andrian or Ulf would like to see people keep using this quirk. > IMHO we probably could totally remove it since bus-width already tells > what the driver needs. Hm, I see what you are saying, the problem is that the core (sdhci_setup_host) falls back to 4-bit if SDHCI_QUIRK_FORCE_1_BIT_DATA is not set... Removing that should be fine for DT enabled SDHC drivers, since mmc_of_parse sets MMC_CAP_4_BIT_DATA. But not sure about drivers which parse dt on their own or still support platform data.... Those might rely on MMC_CAP_4_BIT_DATA being set by default... -- Stefan > > Andrian & Ulf, > Comments? > >> /* call to generic mmc_of_parse to support additional capabilities */ >> ret = mmc_of_parse(host->mmc); >> if (ret) >> -- >> 2.7.4 >> > > Regards > Dong Aisheng