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The intention for this patch is to help folks debug the failure like this: dwmmc_rockchip fe320000.dwmmc: IDMAC supports 32-bit address mode. dwmmc_rockchip fe320000.dwmmc: Using internal DMA controller. dwmmc_rockchip fe320000.dwmmc: Version ID is 270a dwmmc_rockchip fe320000.dwmmc: DW MMC controller at irq 28,32 bit host data width,256 deep fifo dwmmc_rockchip fe320000.dwmmc: Got CD GPIO mmc_host mmc0: Bus speed (slot 0) = 400000Hz (slot req 400000Hz, actual 400000HZ div = 0) mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 50000000Hz, actual 50000000HZ div = 0) mmc0: new high speed SDHC card at address 0007 mmcblk: probe of mmc0:0007 failed with error -28 The reason may be some buggy userspace daemon miss the disk remove uevent sometimes so it would finally make the SD card not work. So from the dmesg it only shows a errno of -28 but still don't understand what happened. For quick reproduce this, we could set max_devices to 8 and run for i in $(seq 1 9); do echo "========================" $i echo fe320000.dwmmc > /sys/bus/platform/drivers/dwmmc_rockchip/unbind sleep .5 echo fe320000.dwmmc > /sys/bus/platform/drivers/dwmmc_rockchip/bind sleep .5 mount -t vfat /dev/mmcblk0 /mnt sleep .5 done Another possible reason would be the device has more partitions than what we support, so that they have to increase their max_devices. Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.