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Diffstat (limited to 'Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt')
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diff --git a/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt b/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt new file mode 100644 index 000000000..76bf087bc --- /dev/null +++ b/Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt @@ -0,0 +1,112 @@ +* TI Highspeed MMC host controller for OMAP + +The Highspeed MMC Host Controller on TI OMAP family +provides an interface for MMC, SD, and SDIO types of memory cards. + +This file documents differences between the core properties described +by mmc.txt and the properties used by the omap_hsmmc driver. + +Required properties: +- compatible: + Should be "ti,omap2-hsmmc", for OMAP2 controllers + Should be "ti,omap3-hsmmc", for OMAP3 controllers + Should be "ti,omap3-pre-es3-hsmmc" for OMAP3 controllers pre ES3.0 + Should be "ti,omap4-hsmmc", for OMAP4 controllers + Should be "ti,am33xx-hsmmc", for AM335x controllers +- ti,hwmods: Must be "mmc<n>", n is controller instance starting 1 + +Optional properties: +ti,dual-volt: boolean, supports dual voltage cards +<supply-name>-supply: phandle to the regulator device tree node +"supply-name" examples are "vmmc", "vmmc_aux" etc +ti,non-removable: non-removable slot (like eMMC) +ti,needs-special-reset: Requires a special softreset sequence +ti,needs-special-hs-handling: HSMMC IP needs special setting for handling High Speed +dmas: List of DMA specifiers with the controller specific format +as described in the generic DMA client binding. A tx and rx +specifier is required. +dma-names: List of DMA request names. These strings correspond +1:1 with the DMA specifiers listed in dmas. The string naming is +to be "rx" and "tx" for RX and TX DMA requests, respectively. + +Examples: + +[hwmod populated DMA resources] + + mmc1: mmc@0x4809c000 { + compatible = "ti,omap4-hsmmc"; + reg = <0x4809c000 0x400>; + ti,hwmods = "mmc1"; + ti,dual-volt; + bus-width = <4>; + vmmc-supply = <&vmmc>; /* phandle to regulator node */ + ti,non-removable; + }; + +[generic DMA request binding] + + mmc1: mmc@0x4809c000 { + compatible = "ti,omap4-hsmmc"; + reg = <0x4809c000 0x400>; + ti,hwmods = "mmc1"; + ti,dual-volt; + bus-width = <4>; + vmmc-supply = <&vmmc>; /* phandle to regulator node */ + ti,non-removable; + dmas = <&edma 24 + &edma 25>; + dma-names = "tx", "rx"; + }; + +[workaround for missing swakeup on am33xx] + +This SOC is missing the swakeup line, it will not detect SDIO irq +while in suspend. + + ------ + | PRCM | + ------ + ^ | + swakeup | | fclk + | v + ------ ------- ----- + | card | -- CIRQ --> | hsmmc | -- IRQ --> | CPU | + ------ ------- ----- + +In suspend the fclk is off and the module is disfunctional. Even register reads +will fail. A small logic in the host will request fclk restore, when an +external event is detected. Once the clock is restored, the host detects the +event normally. Since am33xx doesn't have this line it never wakes from +suspend. + +The workaround is to reconfigure the dat1 line as a GPIO upon suspend. To make +this work, we need to set the named pinctrl states "default" and "idle". +Prepare idle to remux dat1 as a gpio, and default to remux it back as sdio +dat1. The MMC driver will then toggle between idle and default state during +runtime. + +In summary: +1. select matching 'compatible' section, see example below. +2. specify pinctrl states "default" and "idle", "sleep" is optional. +3. specify the gpio irq used for detecting sdio irq in suspend + +If configuration is incomplete, a warning message is emitted "falling back to +polling". Also check the "sdio irq mode" in /sys/kernel/debug/mmc0/regs. Mind +not every application needs SDIO irq, e.g. MMC cards. + + mmc1: mmc@48060100 { + compatible = "ti,am33xx-hsmmc"; + ... + pinctrl-names = "default", "idle", "sleep" + pinctrl-0 = <&mmc1_pins>; + pinctrl-1 = <&mmc1_idle>; + pinctrl-2 = <&mmc1_sleep>; + ... + interrupts-extended = <&intc 64 &gpio2 28 0>; + }; + + mmc1_idle : pinmux_cirq_pin { + pinctrl-single,pins = < + 0x0f8 0x3f /* GPIO2_28 */ + >; + }; |