atmel,sam-smc
Vendor: Atmel Corporation
Description
Atmel Static Memory Controller (SMC).
The SMC allows to interface with static-memory mapped external devices such as
SRAM, PSRAM, PROM, EPROM, EEPROM, LCD Module, NOR Flash and NAND Flash.
The SMC is clocked through the Master Clock (MCK) which is controlled by the
Power Management Controller (PMC).
The SMC controller can have up to 4 children defining the connected external
memory devices. The reg property is set to the device's Chip Select.
Device Tree example taken from the sam4_xplained board:
&smc {
status = "okay";
pinctrl-0 = <&smc_default>;
pinctrl-names = "default";
is66wv51216dbll@0 {
reg = <0>;
atmel,smc-write-mode = "nwe";
atmel,smc-read-mode = "nrd";
atmel,smc-setup-timing = <1 1 1 1>;
atmel,smc-pulse-timing = <6 6 6 6>;
atmel,smc-cycle-timing = <7 7>;
};
};
The above example configures a is66wv51216dbll-55 device. The device is a
low power static RAM which uses NWE and NRD signals connected to the WE
and OE inputs respectively. Assuming that MCK is 120MHz (cpu at full speed)
each MCK cycle will be equivalent to 8ns. Since the memory full cycle is
55ns, as per specification, it requires atmel,smc-cycle-timing of at least
7 pulses (56ns). The atmel,smc-cycle-timing is composed of three parts:
setup, pulse and hold. The setup is used to address the memory. The pulse
is the time used to read/write. The hold is used to release memory. For the
is66wv51216dbll-55 a minimum setup of 5ns (1 cycle) with at least 45ns
(6 cycles) for CPU read/write and no hold time is required.
Note: Since no hold parameter is available at SMC the atmel,smc-cycle-timing
should have additional cycles to accommodate for hold values.
No Hold Time:
cycle-timing (7) = setup (1) + pulse (6) + hold (0)
With 3 Hold Times:
cycle-timing (10) = setup (1) + pulse (6) + hold (3)
Finally, in order to make the memory available you will need to define new
memory device/s in DeviceTree:
sram1: sram@60000000 {
compatible = "zephyr,memory-region", "mmio-sram";
device_type = "memory";
reg = <0x60000000 DT_SIZE_K(512)>;
zephyr,memory-region = "SRAM1";
};
Properties
Top level properties
These property descriptions apply to “atmel,sam-smc” nodes themselves. This page also describes child node properties in the following sections.
Properties not inherited from the base binding file.
Name |
Type |
Details |
|---|---|---|
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Pin configuration/s for the first state. Content is specific to the
selected pin controller driver implementation.
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Pin configuration/s for the second state. See pinctrl-0.
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Pin configuration/s for the third state. See pinctrl-0.
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Pin configuration/s for the fourth state. See pinctrl-0.
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Pin configuration/s for the fifth state. See pinctrl-0.
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Names for the provided states. The number of names needs to match the
number of states.
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Deprecated properties not inherited from the base binding file.
(None)
Properties inherited from the base binding file, which defines common properties that may be set on many nodes. Not all of these may apply to the “atmel,sam-smc” compatible.
Name |
Type |
Details |
|---|---|---|
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Property to identify that a device can be used as wake up source.
When this property is provided a specific flag is set into the
device that tells the system that the device is capable of
wake up the system.
Wake up capable devices are disabled (interruptions will not wake up
the system) by default but they can be enabled at runtime if necessary.
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Power domain the device belongs to.
The device will be notified when the power domain it belongs to is either
suspended or resumed.
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Automatically configure the device for runtime power management after the
init function runs.
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List of power states that will disable this device power.
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indicates the operational status of a device
Legal values: See Important properties for more information. |
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compatible strings
This property is required. See Important properties for more information. |
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register space
This property is required. See Important properties for more information. |
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name of each register space
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interrupts for device
See Important properties for more information. |
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extended interrupt specifier for device
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name of each interrupt
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phandle to interrupt controller node
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Human readable string describing the device (used as device_get_binding() argument)
See Important properties for more information. This property is deprecated. |
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Clock gate information
This property is required. |
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name of each clock
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number of address cells in reg property
This property is required. Constant value: |
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number of size cells in reg property
This property is required. |
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DMA channels specifiers
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Provided names of DMA channel specifiers
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IO channels specifiers
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Provided names of IO channel specifiers
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mailbox / IPM channels specifiers
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Provided names of mailbox / IPM channel specifiers
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Do not initialize device automatically on boot. Device should be manually
initialized using device_init().
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Child node properties
Name |
Type |
Details |
|---|---|---|
|
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The device's SMC Chip Select number.
Valid range: 0 - 3
This property is required. See Important properties for more information. |
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Select which signal is used for the write operation, either the chip
select (ncs) or a dedicated write enable pin (nwe). The data is put
on the bus during the pulse and hold steps of that signal.
The internal data buffers are switched to output mode after the NCS_WR
or NWE setup time.
This property is required. Legal values: |
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Select which signal is used for the read operation, either the chip
select (ncs) or a dedicated output enable pin (nrd). The data is read
from the bus during the pulse and hold steps of that signal.
This property is required. Legal values: |
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This value is used to setup memory region (set address). The setup
values is an array of the signals NWE, NCS_WR, NRD and NCS_RD
where each value is configured in terms of MCK cycles. The SMC
controller allows use of setups value of 0 (no delays) when
consecutive reads/writes are used. Each value is encoded in
6 bits where the highest bit adds an offset of 128 cycles.
The effective value for each element is: 128 x setup[5] + setup[4:0]
This property is required. |
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This value is used to effectivelly read/write at memory region (pulse phase).
The pulse value is an array of the signals NWE, NCS_WR, NRD and NCS_RD where
each value is configured in terms of MCK cycles and a value of 0 is forbidden.
Each value is encoded in 7 bits where the highest bit adds an offset of 256
cycles. The effective value for each element is: 256 x setup[6] + setup[5:0]
This property is required. |
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SMC timing configurations in cycles for the total write and read
length respectively.
This value describes the entire write/read operation timing which
is defined as: cycle = setup + pulse + hold
Value has to be greater or equal to setup + pulse timing and
is encoded in 9 bits where the two highest bits are multiplied
with an offset of 256.
Effective value for each element: 256 x cycle[8:7] + cycle[6:0]
This property is required. |