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The "disable-wp" property is used to specify that a given SD card slot doesn't have a concept of write protect. This eliminates the need for special case code for SD slots that should never be write protected (like a micro SD slot or a dev board). The dw_mmc driver is special in needing to specify "disable-wp" because the lack of a "wp-gpios" property means to use the special purpose write protect line. On some other mmc devices the lack of "wp-gpios" means that write protect should be disabled. Signed-off-by: Doug Anderson <dianders@chromium.org> Acked-by: Seungwon Jeon <tgih.jun@samsung.com> Acked-by: Will Newton <will.newton@imgtec.com> Acked-by: Olof Johansson <olof@lixom.net> Signed-off-by: Chris Ball <cjb@laptop.org>
88 lines
3.1 KiB
Plaintext
88 lines
3.1 KiB
Plaintext
* Synopsis Designware Mobile Storage Host Controller
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The Synopsis designware mobile storage host controller is used to interface
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a SoC with storage medium such as eMMC or SD/MMC cards. This file documents
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differences between the core mmc properties described by mmc.txt and the
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properties used by the Synopsis Designware Mobile Storage Host Controller.
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Required Properties:
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* compatible: should be
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- snps,dw-mshc: for controllers compliant with synopsis dw-mshc.
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* #address-cells: should be 1.
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* #size-cells: should be 0.
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# Slots: The slot specific information are contained within child-nodes with
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each child-node representing a supported slot. There should be atleast one
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child node representing a card slot. The name of the child node representing
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the slot is recommended to be slot@n where n is the unique number of the slot
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connnected to the controller. The following are optional properties which
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can be included in the slot child node.
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* reg: specifies the physical slot number. The valid values of this
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property is 0 to (num-slots -1), where num-slots is the value
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specified by the num-slots property.
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* bus-width: as documented in mmc core bindings.
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* wp-gpios: specifies the write protect gpio line. The format of the
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gpio specifier depends on the gpio controller. If a GPIO is not used
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for write-protect, this property is optional.
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* disable-wp: If the wp-gpios property isn't present then (by default)
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we'd assume that the write protect is hooked up directly to the
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controller's special purpose write protect line (accessible via
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the WRTPRT register). However, it's possible that we simply don't
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want write protect. In that case specify 'disable-wp'.
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NOTE: This property is not required for slots known to always
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connect to eMMC or SDIO cards.
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Optional properties:
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* num-slots: specifies the number of slots supported by the controller.
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The number of physical slots actually used could be equal or less than the
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value specified by num-slots. If this property is not specified, the value
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of num-slot property is assumed to be 1.
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* fifo-depth: The maximum size of the tx/rx fifo's. If this property is not
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specified, the default value of the fifo size is determined from the
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controller registers.
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* card-detect-delay: Delay in milli-seconds before detecting card after card
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insert event. The default value is 0.
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* supports-highspeed: Enables support for high speed cards (upto 50MHz)
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* broken-cd: as documented in mmc core bindings.
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Aliases:
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- All the MSHC controller nodes should be represented in the aliases node using
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the following format 'mshc{n}' where n is a unique number for the alias.
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Example:
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The MSHC controller node can be split into two portions, SoC specific and
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board specific portions as listed below.
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dwmmc0@12200000 {
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compatible = "snps,dw-mshc";
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reg = <0x12200000 0x1000>;
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interrupts = <0 75 0>;
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#address-cells = <1>;
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#size-cells = <0>;
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};
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dwmmc0@12200000 {
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num-slots = <1>;
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supports-highspeed;
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broken-cd;
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fifo-depth = <0x80>;
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card-detect-delay = <200>;
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slot@0 {
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reg = <0>;
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bus-width = <8>;
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};
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};
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