ti-omap-hsmmc.txt

  1* TI Highspeed MMC host controller for OMAP and 66AK2G family.
  2
  3The Highspeed MMC Host Controller on TI OMAP and 66AK2G family
  4provides an interface for MMC, SD, and SDIO types of memory cards.
  5
  6This file documents differences between the core properties described
  7by mmc.txt and the properties used by the omap_hsmmc driver.
  8
  9Required properties:
 10--------------------
 11- compatible:
 12 Should be "ti,omap2-hsmmc", for OMAP2 controllers
 13 Should be "ti,omap3-hsmmc", for OMAP3 controllers
 14 Should be "ti,omap3-pre-es3-hsmmc" for OMAP3 controllers pre ES3.0
 15 Should be "ti,omap4-hsmmc", for OMAP4 controllers
 16 Should be "ti,am33xx-hsmmc", for AM335x controllers
 17 Should be "ti,k2g-hsmmc", "ti,omap4-hsmmc" for 66AK2G controllers.
 18
 19SoC specific required properties:
 20---------------------------------
 21The following are mandatory properties for OMAPs, AM33xx and AM43xx SoCs only:
 22- ti,hwmods: Must be "mmc<n>", n is controller instance starting 1.
 23
 24The following are mandatory properties for 66AK2G SoCs only:
 25- power-domains:Should contain a phandle to a PM domain provider node
 26		and an args specifier containing the MMC device id
 27		value. This property is as per the binding,
 28		Documentation/devicetree/bindings/soc/ti/sci-pm-domain.yaml
 29- clocks:	Must contain an entry for each entry in clock-names. Should
 30		be defined as per the he appropriate clock bindings consumer
 31		usage in Documentation/devicetree/bindings/clock/ti,sci-clk.yaml
 32- clock-names:	Shall be "fck" for the functional clock,
 33		and "mmchsdb_fck" for the debounce clock.
 34
 35
 36Optional properties:
 37--------------------
 38- ti,dual-volt:		boolean, supports dual voltage cards
 39- <supply-name>-supply:	phandle to the regulator device tree node
 40			  "supply-name" examples are "vmmc",
 41			  "vmmc_aux"(deprecated)/"vqmmc" etc
 42- ti,non-removable:	non-removable slot (like eMMC)
 43- ti,needs-special-reset:	Requires a special softreset sequence
 44- ti,needs-special-hs-handling:	HSMMC IP needs special setting
 45				  for handling High Speed
 46- dmas:			List of DMA specifiers with the controller specific
 47			format as described in the generic DMA client
 48			binding. A tx and rx specifier is required.
 49- dma-names:		List of DMA request names. These strings correspond
 50			1:1 with the DMA specifiers listed in dmas.
 51			The string naming is to be "rx" and "tx" for
 52			RX and TX DMA requests, respectively.
 53
 54Examples:
 55
 56[hwmod populated DMA resources]
 57
 58	mmc1: mmc@4809c000 {
 59		compatible = "ti,omap4-hsmmc";
 60		reg = <0x4809c000 0x400>;
 61		ti,hwmods = "mmc1";
 62		ti,dual-volt;
 63		bus-width = <4>;
 64		vmmc-supply = <&vmmc>; /* phandle to regulator node */
 65		ti,non-removable;
 66	};
 67
 68[generic DMA request binding]
 69
 70	mmc1: mmc@4809c000 {
 71		compatible = "ti,omap4-hsmmc";
 72		reg = <0x4809c000 0x400>;
 73		ti,hwmods = "mmc1";
 74		ti,dual-volt;
 75		bus-width = <4>;
 76		vmmc-supply = <&vmmc>; /* phandle to regulator node */
 77		ti,non-removable;
 78		dmas = <&edma 24
 79			&edma 25>;
 80		dma-names = "tx", "rx";
 81	};
 82
 83[workaround for missing swakeup on am33xx]
 84
 85This SOC is missing the swakeup line, it will not detect SDIO irq
 86while in suspend.
 87
 88                             ------
 89                             | PRCM |
 90                              ------
 91                               ^ |
 92                       swakeup | | fclk
 93                               | v
 94       ------                -------               -----
 95      | card | -- CIRQ -->  | hsmmc | -- IRQ -->  | CPU |
 96       ------                -------               -----
 97
 98In suspend the fclk is off and the module is dysfunctional. Even register reads
 99will fail. A small logic in the host will request fclk restore, when an
100external event is detected. Once the clock is restored, the host detects the
101event normally. Since am33xx doesn't have this line it never wakes from
102suspend.
103
104The workaround is to reconfigure the dat1 line as a GPIO upon suspend. To make
105this work, we need to set the named pinctrl states "default" and "idle".
106Prepare idle to remux dat1 as a gpio, and default to remux it back as sdio
107dat1. The MMC driver will then toggle between idle and default state during
108runtime.
109
110In summary:
1111. select matching 'compatible' section, see example below.
1122. specify pinctrl states "default" and "idle", "sleep" is optional.
1133. specify the gpio irq used for detecting sdio irq in suspend
114
115If configuration is incomplete, a warning message is emitted "falling back to
116polling". Also check the "sdio irq mode" in /sys/kernel/debug/mmc0/regs. Mind
117not every application needs SDIO irq, e.g. MMC cards.
118
119	mmc1: mmc@48060100 {
120		compatible = "ti,am33xx-hsmmc";
121		...
122		pinctrl-names = "default", "idle", "sleep"
123		pinctrl-0 = <&mmc1_pins>;
124		pinctrl-1 = <&mmc1_idle>;
125		pinctrl-2 = <&mmc1_sleep>;
126		...
127		interrupts-extended = <&intc 64 &gpio2 28 IRQ_TYPE_LEVEL_LOW>;
128	};
129
130	mmc1_idle : pinmux_cirq_pin {
131		pinctrl-single,pins = <
132		        0x0f8 0x3f      /* GPIO2_28 */
133		>;
134	};