Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934589AbZFMBGf (ORCPT ); Fri, 12 Jun 2009 21:06:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753263AbZFMBG2 (ORCPT ); Fri, 12 Jun 2009 21:06:28 -0400 Received: from ey-out-1920.google.com ([74.125.78.144]:32479 "EHLO ey-out-1920.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750851AbZFMBG1 (ORCPT ); Fri, 12 Jun 2009 21:06:27 -0400 MIME-Version: 1.0 Date: Fri, 12 Jun 2009 18:06:29 -0700 X-Google-Sender-Auth: ea06005acb97efac Message-ID: Subject: [PATCH 4/6] Unified AVR32/AT91 MCI Driver Clock Divisor Cap From: Rob Emanuele To: Haavard Skinnemoen Cc: Andrew Victor , Nicolas Ferre , linux-arm-kernel@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org, drzeus-mmc@drzeus.cx Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2764 Lines: 85 This patch adds the compile time configuration option for the atmel-mci driver to cap the MCI CLKDIV register value to a minimum value. This is useful for debugging and for boards that have a long mci clock line. Please read the whole set, try it out, and comment. Thank you, Rob Emanuele --- drivers/mmc/host/Kconfig | 14 ++++++++++++++ drivers/mmc/host/atmel-mci.c | 10 ++++++++++ 2 files changed, 24 insertions(+), 0 deletions(-) diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig index 9e24029..9f797b2 100644 --- a/drivers/mmc/host/Kconfig +++ b/drivers/mmc/host/Kconfig @@ -150,6 +150,20 @@ config MMC_ATMELMCI endchoice +config MMC_ATMELMCI_CLKDIV_CAP + int "Cap the CLKDIV to keep the controller from going too fast." + depends on MMC_ATMELMCI + default 0 + range 0 255 + help + This is the lowest value the clock divisor for the MMC + controller can be. Value is between 0 and 255. + MCI_CK = MCK/(2*(CLKDIV+1)) + Raising this value may improve your controller's reliability + at the cost of speed. + + If unsure, leave at 0. + config MMC_ATMELMCI_ALWAYS_RESET bool "Reset before every request. Sometimes needed for buggy chips." depends on MMC_ATMELMCI diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c index b133baa..1c1a4b3 100644 --- a/drivers/mmc/host/atmel-mci.c +++ b/drivers/mmc/host/atmel-mci.c @@ -74,6 +74,10 @@ struct atmel_mci_dma { #define MMC_ALWAYS_RESET 0 #endif +#ifndef CONFIG_MMC_ATMELMCI_CLKDIV_CAP +#define CONFIG_MMC_ATMELMCI_CLKDIV_CAP 0 +#endif + /** * struct atmel_mci - MMC controller state shared between all slots * @lock: Spinlock protecting the queue and associated data. @@ -876,6 +880,12 @@ static void atmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) clock_min, host->bus_hz / (2 * 256)); clkdiv = 255; } + if (clkdiv < CONFIG_MMC_ATMELMCI_CLKDIV_CAP) { + dev_warn(&mmc->class_dev, + "clkdiv %u too fast; capped using %u\n", + clkdiv, CONFIG_MMC_ATMELMCI_CLKDIV_CAP); + clkdiv = CONFIG_MMC_ATMELMCI_CLKDIV_CAP; - Show quoted text - + } host->mode_reg = MCI_MR_CLKDIV(clkdiv); -- 1.6.0.4 -- Robert Emanuele Crystalfontz America, Inc. www.crystalfontz.com rje@crystalfontz.com +1 509 892 1200 -- 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/