[rv_plic] Adjust naming of PRIO regs by using multireg #25701
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Now that we have non-compact multireg features, use them to eliminate the explicit numbering of CSRs from the template and improve Rust code generation. Signed-off-by: Alexander Williams <awill@opentitan.org>
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| rv_plic_reg2hw_prio183_reg_t prio183; // [206:205] | ||
| rv_plic_reg2hw_prio184_reg_t prio184; // [204:203] | ||
| rv_plic_reg2hw_prio185_reg_t prio185; // [202:201] | ||
| rv_plic_reg2hw_prio_mreg_t [185:0] prio; // [572:201] |
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Same question here about the length and bit-length.
| rv_plic_reg2hw_prio157_reg_t prio157; // [180:179] | ||
| rv_plic_reg2hw_prio158_reg_t prio158; // [178:177] | ||
| rv_plic_reg2hw_prio159_reg_t prio159; // [176:175] | ||
| rv_plic_reg2hw_prio_mreg_t [159:0] prio; // [494:175] |
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At first glance, it looks to me like the [159:0] and the // [494:201] here disagree, since the comment indicates a 320-bit range. Is this maybe an array of two-bit multireg entries that has length 160 but bit-length 320? But the multireg entry below has [159:0] and // [174:15], which match exactly with length and bit-length 160. I'm not an RTL expert so I'm probably missing something here, but wanted to double-check 🙂
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Yes, that's exactly right. This is a definition of an array of rv_plic_reg2hw_prio_mreg_t, which is defined above as a struct with a single 2-bit member (with the member named q).
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From a software perspective, the interesting bit here is how the output of With the multireg construction, reggen will generate an array for the Rust struct instead of the flattened variant. Without this, each priority register gets a named member in the IP's register definitions, which is just a little less nice to work with. (since Rust provides iterators and other helpful constructions if the type is a sized aggregate -- in C, we'd just use pointer arithmetic, heh) I noticed the incongruity with the other CSRs as I was fiddling with topgen for other reasons and figured, "Why not make this little tweak?" ;) |
Now that we have non-compact multireg features, use them to eliminate the explicit numbering of CSRs from the template and improve Rust code generation.