Add builder API for FlexRAM bank layout

The layout, or assignment of FlexRAM banks to memory regions, is more
precise than the count. When a user specifies the count, we still apply
the same layout as we always have. But now, by default, we prefer the
fuse layout for users who have made no choice.

This commit supports RAM loading with probe-rs. After probe-rs resets
the MCU and uses the fuse FlexRAM layout, firmware can perfectly match
that layout without disrupting the data already copied into RAM by the
debugger.

1 files changed, 7 insertions, 5 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 7ec6557..ab55627 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -139,11 +139,13 @@
 //!
 //! # Limitations
 //!
-//! The crate considers the assignment of FlexRAM memory banks to ITCM/DTCM/OCRAM
-//! an implementation detail. Additionally, the implementation does not care
-//! about the assignment of memory bank power domains. This seems to matter most on
-//! the 1050, which has the widest spread of bank-to-power domain assignment
-//! (according to AN12077).
+//! By default, the crate considers the assignment of FlexRAM memory banks to
+//! ITCM/DTCM/OCRAM an implementation detail. If you must define the assignment,
+//! you can specify your own layout by using [`flexram_layout`](RuntimeBuilder::flexram_layout).
+//!
+//! Additionally, the implementation does not care about the assignment of memory bank power
+//! domains. This seems to matter most on the 1050, which has the widest spread of bank-to-power
+//! domain assignment (according to AN12077).
 //!
 //! There is no support for ECC on 1160 or 1170. The runtime assumes that OCRAM and TCM ECC
 //! is disabled, and that the corresponding memory banks can be used for OCRAM.