1# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) 2%YAML 1.2 3--- 4$id: http://devicetree.org/schemas/bus/qcom,ebi2.yaml# 5$schema: http://devicetree.org/meta-schemas/core.yaml# 6 7title: Qualcomm External Bus Interface 2 (EBI2) 8 9description: | 10 The EBI2 contains two peripheral blocks: XMEM and LCDC. The XMEM handles any 11 external memory (such as NAND or other memory-mapped peripherals) whereas 12 LCDC handles LCD displays. 13 14 As it says it connects devices to an external bus interface, meaning address 15 lines (up to 9 address lines so can only address 1KiB external memory space), 16 data lines (16 bits), OE (output enable), ADV (address valid, used on some 17 NOR flash memories), WE (write enable). This on top of 6 different chip selects 18 (CS0 thru CS5) so that in theory 6 different devices can be connected. 19 20 Apparently this bus is clocked at 64MHz. It has dedicated pins on the package 21 and the bus can only come out on these pins, however if some of the pins are 22 unused they can be left unconnected or remuxed to be used as GPIO or in some 23 cases other orthogonal functions as well. 24 25 Also CS1 and CS2 has -A and -B signals. Why they have that is unclear to me. 26 27 The chip selects have the following memory range assignments. This region of 28 memory is referred to as "Chip Peripheral SS FPB0" and is 168MB big. 29 30 Chip Select Physical address base 31 CS0 GPIO134 0x1a800000-0x1b000000 (8MB) 32 CS1 GPIO39 (A) / GPIO123 (B) 0x1b000000-0x1b800000 (8MB) 33 CS2 GPIO40 (A) / GPIO124 (B) 0x1b800000-0x1c000000 (8MB) 34 CS3 GPIO133 0x1d000000-0x25000000 (128 MB) 35 CS4 GPIO132 0x1c800000-0x1d000000 (8MB) 36 CS5 GPIO131 0x1c000000-0x1c800000 (8MB) 37 38 The APQ8060 Qualcomm Application Processor User Guide, 80-N7150-14 Rev. A, 39 August 6, 2012 contains some incomplete documentation of the EBI2. 40 41 FIXME: the manual mentions "write precharge cycles" and "precharge cycles". 42 We have not been able to figure out which bit fields these correspond to 43 in the hardware, or what valid values exist. The current hypothesis is that 44 this is something just used on the FAST chip selects and that the SLOW 45 chip selects are understood fully. There is also a "byte device enable" 46 flag somewhere for 8bit memories. 47 48 FIXME: The chipselects have SLOW and FAST configuration registers. It's a bit 49 unclear what this means, if they are mutually exclusive or can be used 50 together, or if some chip selects are hardwired to be FAST and others are SLOW 51 by design. 52 53 The XMEM registers are totally undocumented but could be partially decoded 54 because the Cypress AN49576 Antioch Westbridge apparently has suspiciously 55 similar register layout, see: http://www.cypress.com/file/105771/download 56 57maintainers: 58 - Bjorn Andersson <andersson@kernel.org> 59 60properties: 61 compatible: 62 enum: 63 - qcom,apq8060-ebi2 64 - qcom,msm8660-ebi2 65 66 reg: 67 items: 68 - description: EBI2 config region 69 - description: XMEM config region 70 71 reg-names: 72 items: 73 - const: ebi2 74 - const: xmem 75 76 ranges: true 77 78 clocks: 79 items: 80 - description: EBI_2X clock 81 - description: EBI clock 82 83 clock-names: 84 items: 85 - const: ebi2x 86 - const: ebi2 87 88 '#address-cells': 89 const: 2 90 91 '#size-cells': 92 const: 1 93 94required: 95 - compatible 96 - reg 97 - reg-names 98 - ranges 99 - clocks 100 - clock-names 101 - '#address-cells' 102 - '#size-cells' 103 104patternProperties: 105 "^.*@[0-5],[0-9a-f]+$": 106 type: object 107 additionalProperties: true 108 properties: 109 reg: 110 maxItems: 1 111 112 # SLOW chip selects 113 qcom,xmem-recovery-cycles: 114 $ref: /schemas/types.yaml#/definitions/uint32 115 description: > 116 The time the memory continues to drive the data bus after OE 117 is de-asserted, in order to avoid contention on the data bus. 118 They are inserted when reading one CS and switching to another 119 CS or read followed by write on the same CS. Minimum value is 120 actually 1, so a value of 0 will still yield 1 recovery cycle. 121 minimum: 0 122 maximum: 15 123 124 qcom,xmem-write-hold-cycles: 125 $ref: /schemas/types.yaml#/definitions/uint32 126 description: > 127 The extra cycles inserted after every write minimum 1. The 128 data out is driven from the time WE is asserted until CS is 129 asserted. With a hold of 1 (value = 0), the CS stays active 130 for 1 extra cycle, etc. 131 minimum: 0 132 maximum: 15 133 134 qcom,xmem-write-delta-cycles: 135 $ref: /schemas/types.yaml#/definitions/uint32 136 description: > 137 The initial latency for write cycles inserted for the first 138 write to a page or burst memory. 139 minimum: 0 140 maximum: 255 141 142 qcom,xmem-read-delta-cycles: 143 $ref: /schemas/types.yaml#/definitions/uint32 144 description: > 145 The initial latency for read cycles inserted for the first 146 read to a page or burst memory. 147 minimum: 0 148 maximum: 255 149 150 qcom,xmem-write-wait-cycles: 151 $ref: /schemas/types.yaml#/definitions/uint32 152 description: > 153 The number of wait cycles for every write access. 154 minimum: 0 155 maximum: 15 156 157 qcom,xmem-read-wait-cycles: 158 $ref: /schemas/types.yaml#/definitions/uint32 159 description: > 160 The number of wait cycles for every read access. 161 minimum: 0 162 maximum: 15 163 164 165 # FAST chip selects 166 qcom,xmem-address-hold-enable: 167 $ref: /schemas/types.yaml#/definitions/uint32 168 description: > 169 Holds the address for an extra cycle to meet hold time 170 requirements with ADV assertion, when set to 1. 171 enum: [ 0, 1 ] 172 173 qcom,xmem-adv-to-oe-recovery-cycles: 174 $ref: /schemas/types.yaml#/definitions/uint32 175 description: > 176 The number of cycles elapsed before an OE assertion, with 177 respect to the cycle where ADV (address valid) is asserted. 178 minimum: 0 179 maximum: 3 180 181 qcom,xmem-read-hold-cycles: 182 $ref: /schemas/types.yaml#/definitions/uint32 183 description: > 184 The length in cycles of the first segment of a read transfer. 185 For a single read transfer this will be the time from CS 186 assertion to OE assertion. 187 minimum: 0 188 maximum: 15 189 190 required: 191 - reg 192 193additionalProperties: false 194 195examples: 196 - | 197 #include <dt-bindings/clock/qcom,gcc-msm8660.h> 198 #include <dt-bindings/interrupt-controller/irq.h> 199 #include <dt-bindings/gpio/gpio.h> 200 201 external-bus@1a100000 { 202 compatible = "qcom,msm8660-ebi2"; 203 reg = <0x1a100000 0x1000>, <0x1a110000 0x1000>; 204 reg-names = "ebi2", "xmem"; 205 ranges = <0 0x0 0x1a800000 0x00800000>, 206 <1 0x0 0x1b000000 0x00800000>, 207 <2 0x0 0x1b800000 0x00800000>, 208 <3 0x0 0x1d000000 0x08000000>, 209 <4 0x0 0x1c800000 0x00800000>, 210 <5 0x0 0x1c000000 0x00800000>; 211 212 clocks = <&gcc EBI2_2X_CLK>, <&gcc EBI2_CLK>; 213 clock-names = "ebi2x", "ebi2"; 214 215 #address-cells = <2>; 216 #size-cells = <1>; 217 218 ethernet@2,0 { 219 compatible = "smsc,lan9221", "smsc,lan9115"; 220 reg = <2 0x0 0x100>; 221 222 interrupts-extended = <&pm8058_gpio 7 IRQ_TYPE_EDGE_FALLING>, 223 <&tlmm 29 IRQ_TYPE_EDGE_RISING>; 224 reset-gpios = <&tlmm 30 GPIO_ACTIVE_LOW>; 225 226 phy-mode = "mii"; 227 reg-io-width = <2>; 228 smsc,force-external-phy; 229 smsc,irq-push-pull; 230 231 /* SLOW chipselect config */ 232 qcom,xmem-recovery-cycles = <0>; 233 qcom,xmem-write-hold-cycles = <3>; 234 qcom,xmem-write-delta-cycles = <31>; 235 qcom,xmem-read-delta-cycles = <28>; 236 qcom,xmem-write-wait-cycles = <9>; 237 qcom,xmem-read-wait-cycles = <9>; 238 }; 239 }; 240