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Added custom WFE instruction plus related wu_i pin. Made misa.X always 1 #639

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merged 3 commits into from
Aug 16, 2022
Merged

Added custom WFE instruction plus related wu_i pin. Made misa.X always 1 #639

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77c12a5
Added custom WFE instruction plus related wu_i pin. Made misa.X always 1
Silabs-ArjanB Aug 8, 2022
df8e6a3
Renamed wu_i to wfe_wu_i
Silabs-ArjanB Aug 8, 2022
b7608e5
Renamed wfe_wu_i pin to wu_wfe_i
Silabs-ArjanB Aug 8, 2022
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3 changes: 2 additions & 1 deletion docs/user_manual/source/control_status_registers.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -511,7 +511,7 @@ Detailed:
+-------------+------------+------------------------------------------------------------------------+
| 24 | WARL (0x0) | **Y** (Reserved). |
+-------------+------------+------------------------------------------------------------------------+
| 23 | WARL | **X** (Non-standard extensions present). |
| 23 | WARL (0x1) | **X** (Non-standard extensions present). |
+-------------+------------+------------------------------------------------------------------------+
| 22 | WARL (0x0) | **W** (Reserved). |
+-------------+------------+------------------------------------------------------------------------+
Expand Down Expand Up @@ -569,6 +569,7 @@ All bitfields in the ``misa`` CSR read as 0 except for the following:
* **E** = 1 if ``RV32`` == RV32E
* **M** = 1 if ``M_EXT`` == M
* **MXL** = 1 (i.e. XLEN = 32)
* **X** = 1
* If ``X_EXT`` == 1, then the value of ``X_MISA`` is ORed into the ``misa`` CSR.

.. note::
Expand Down
7 changes: 5 additions & 2 deletions docs/user_manual/source/integration.rst
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Expand Up @@ -105,7 +105,8 @@ Instantiation Template

// Special control signals
.fetch_enable_i (),
.core_sleep_o ()
.core_sleep_o (),
.wu_wfe_i ()
);

Parameters
Expand Down Expand Up @@ -157,7 +158,7 @@ Parameters
+--------------------------------+----------------+---------------+--------------------------------------------------------------------+
| ``X_MISA`` | logic [31:0] | 32'h0 | MISA extensions implemented on the eXtension interface, |
| | | | see :ref:`csr-misa`. X_MISA can only be used to set a subset of |
| | | | the following: {P, V, F, X, M}. |
| | | | the following: {P, V, F, M}. |
+--------------------------------+----------------+---------------+--------------------------------------------------------------------+
| ``X_ECS_XS`` | logic [1:0] | 2'b0 | Default value for ``mstatus.XS`` if X_EXT = 1, |
| | | | see :ref:`csr-mstatus`. |
Expand Down Expand Up @@ -255,6 +256,8 @@ Interfaces
+-------------------------+-------------------------+-----+--------------------------------------------+
| ``core_sleep_o`` | 1 | out | Core is sleeping, see :ref:`sleep_unit`. |
+-------------------------+-------------------------+-----+--------------------------------------------+
| ``wu_wfe_i`` | 1 | in | Wake-up for ``wfe``, see :ref:`sleep_unit`.|
+-------------------------+-------------------------+-----+--------------------------------------------+
| ``xif_compressed_if`` | eXtension compressed interface, see :ref:`x_compressed_if` |
+-------------------------+----------------------------------------------------------------------------+
| ``xif_issue_if`` | eXtension issue interface, see :ref:`x_issue_if` |
Expand Down
18 changes: 16 additions & 2 deletions docs/user_manual/source/sleep.rst
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Expand Up @@ -14,6 +14,7 @@ The clock gating in the Sleep Unit is impacted by the following:
* ``rst_ni``
* ``fetch_enable_i``
* **wfi** instruction
* **wfe** instruction

:numref:`Sleep Unit interface signals` describes the Sleep Unit interface.

Expand All @@ -26,11 +27,14 @@ The clock gating in the Sleep Unit is impacted by the following:
| Signal | Direction | Description |
+======================================+===========+==================================================+
| ``core_sleep_o`` | output | Core is sleeping because |
| | | of a **wfi** instruction. If |
| | | of a **wfi** or **wfe** instruction. If |
| | | ``core_sleep_o`` = 1, then ``clk_i`` is gated |
| | | off internally and it is allowed to gate off |
| | | ``clk_i`` externally as well. See |
| | | :ref:`wfi` for details. |
| | | :ref:`wfi` and :ref:`wfe` for details. |
+--------------------------------------+-----------+--------------------------------------------------+
| ``wu_wfe_i`` | input | Wake-up signal for custom **wfe** instruction. |
| | | See :ref:`wfe` for details. |
+--------------------------------------+-----------+--------------------------------------------------+

Startup behavior
Expand Down Expand Up @@ -78,3 +82,13 @@ will not become 1.
:align: center

**wfi** example

.. _wfe:

WFE
---

The custom **wfe** instruction behaves exactly as the **wfi** instruction, except that a wake-up can additionally be triggered
by asserting ``wu_wfe_i``.

The **wfe** instruction is encoded as a custom SYSTEM instruction with opcode ``0x8C00_0073``.