Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752098Ab0KIFjt (ORCPT ); Tue, 9 Nov 2010 00:39:49 -0500 Received: from sm-d311v.smileserver.ne.jp ([203.211.202.206]:9021 "EHLO sm-d311v.smileserver.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751448Ab0KIFjp (ORCPT ); Tue, 9 Nov 2010 00:39:45 -0500 Message-ID: <4CD8DE9C.4040505@dsn.okisemi.com> Date: Tue, 09 Nov 2010 14:39:40 +0900 From: Tomoya MORINAGA User-Agent: Mozilla/5.0 (X11; U; Linux i686; ja; rv:1.9.1.11) Gecko/20100711 Thunderbird/3.0.6 MIME-Version: 1.0 To: linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org CC: "Andrew\"" , kok.howg.ewe@intel.com Subject: A MMC card transfer issue Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2467 Lines: 60 I am facing the issue about some MMC cards on Intel EG20T PCH (Platform Controller Hub). The linux version is 2.6.36. I can not transfer data the MMC cards (e.g. Transcned MMC card). The card is 1 bit bus width. And the card is according to MMC specification V3.x. And the EG20T has a 4 bit bus width capability Linux MMC standard driver decides the card bus width as 4 bit, if the MMC specification version is larger than or equal to V4.0 like below. linux/drivers/mmc/core/mmc.c 505 /* 506 * Activate wide bus (if supported). 507 */ 508 if ((card->csd.mmca_vsn >= CSD_SPEC_VER_4) && 509 (host->caps & (MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA))) { 510 unsigned ext_csd_bit, bus_width; 511 512 if (host->caps & MMC_CAP_8_BIT_DATA) { 513 ext_csd_bit = EXT_CSD_BUS_WIDTH_8; 514 bus_width = MMC_BUS_WIDTH_8; 515 } else { 516 ext_csd_bit = EXT_CSD_BUS_WIDTH_4; 517 bus_width = MMC_BUS_WIDTH_4; 518 } 519 520 err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, 521 EXT_CSD_BUS_WIDTH, ext_csd_bit); 522 523 if (err && err != -EBADMSG) 524 goto free_card; 525 526 if (err) { 527 printk(KERN_WARNING "%s: switch to bus width %d " 528 "failed\n", mmc_hostname(card->host), 529 1 << bus_width); 530 err = 0; 531 } else { 532 mmc_set_bus_width(card->host, bus_width); 533 } 534 } 535 However the MMC specification version id is the same as V3.x and V4.0. Therefore the driver uses the 4 bit bus width for the MMC card even if the card has only 1 bit bus width. I modified the driver to use 1 bit bus width only tentatively and confirmed that we can mount the card and R/W correctly. I think we can not support MMC_CAP_4_BIT_DATA or MMC_CAP_8_BIT_DATA in MMC V4.0. How do you think ? -- Thanks, Tomoya MORINAGA(OKI SEMICONDUCTOR CO., LTD.) -- 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/