Messages in this thread Patch in this message |  | | | From | Rob Emanuele <> | | Subject | [PATCH 4/6] atmel-mci: CLKDIV cap to restrict the MCI controller speed | | Date | Tue, 16 Jun 2009 17:54:37 -0700 |
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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.
Signed-off-by: Rob Emanuele <rob@emanuele.us> --- 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 5875125..b628037 100644 --- a/drivers/mmc/host/Kconfig +++ b/drivers/mmc/host/Kconfig @@ -161,6 +161,20 @@ 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 e5894f6..601dae7 100644 --- a/drivers/mmc/host/atmel-mci.c +++ b/drivers/mmc/host/atmel-mci.c @@ -72,6 +72,10 @@ 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. @@ -882,6 +886,12 @@ 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; + } host->mode_reg = MCI_MR_CLKDIV(clkdiv); -- 1.6.0.4
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