Remove Smaiae extension #622 #640
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The AIA spec describes a minimal implementation of mvip and mvien, which does not carry a significant area penalty. The Smaiae section is removed, and a Smaclic/Ssaclic section "Area impact of AIA features" explains how area can be reduced when needed.
christian-herber-nxp
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dependencies need to be updated
src/aclic.adoc
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| == Advanced Core Local Interrupt Controller (Smaclic and Ssaclic) | ||
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| The Smaclic and Ssaclic extensions depend on the Smaiae extension. |
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This needs to be removed.
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Instead, dependence on indirect CSR needs to be added.
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The Smnip section is also stated to have an Smaiae dependency. I have changed that to an Smaclic dependency because the section on State enables refers to an ACLIC bit.
However as written Smnip only really depends on AIA; I'll open an issue to discuss whether it should be an extension in its own right.
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It should only depend on AIA. The state enable bit is a secondary concern. We will have to see down the road if every extension gets its own state enable bit. But I do not view this bit as only present when Smaclic is present.
Signed-off-by: Christian Herber <[email protected]>
src/aclic.adoc
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| | Smtp | (x)| (x)| | | | | ||
| | Smaclic | x | | x | | | | ||
| | Ssaclic | | x | | x | x | | ||
| | Smnip | | | | | x | |
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needs the AIA dependency
src/aclic.adoc
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| in which case a virtual instruction exception is raised | ||
| when in VS or VU mode instead of an illegal instruction exception. | ||
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| NOTE: Many AIA features like programmable IPRIO may not be needed in resource constrained systems. |
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I do not think this is the right place for this note.
It should be right where the dependency to AIA is introduced.
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As described in #622 there is no need for explicit Smaiae and Ssaia extensions because ACLIC extension can be based directly on AIA - there is no need to delete AIA features. AIA provides sufficient scope for area-reduction on resource-constrained systems, e.g. by reducing the number of IPRIO bits (possibly to zero), and by recommending a minimal implementation of mvip.
A note has been added, pointing readers to parts of the AIA spec that assist with area reduction.