#4159 assigned enhancement

Document the fast text and data sections in the user manual

Reported by: Sebastian Huber Owned by: Sebastian Huber
Priority: normal Milestone: 6.1
Component: doc Version: 6
Severity: normal Keywords:
Cc: Blocked By:
Blocking:

Description

On 21/10/20 4:51 pm, Sebastian Huber wrote:

On 21/10/2020 07:42, Chris Johns wrote:

On 21/10/20 4:31 pm, Sebastian Huber wrote:

On 21/10/2020 02:25, Chris Johns wrote:

On 21/10/20 3:04 am, Sebastian Huber wrote:

---

bsps/arm/shared/start/linkcmds.base | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/bsps/arm/shared/start/linkcmds.base
b/bsps/arm/shared/start/linkcmds.base
index d0663cf97e..8fa127ce08 100644
--- a/bsps/arm/shared/start/linkcmds.base
+++ b/bsps/arm/shared/start/linkcmds.base
@@ -290,7 +290,7 @@ SECTIONS {

.fast_text : ALIGN_WITH_INPUT {

bsp_section_fast_text_begin = .;

What is fast text (and fast data)? I have not heard of this before and I
cannot find anything on it?

I added this section 11 years ago as a section for code which could reside in a
faster memory. For example, normal code could reside on a 16-bit SDRAM and the
fast code on an internal 32-bit SRAM in a chip without a cache. In the recent
Cortex-M7 BSPs, the fast text is mapped to the ITCM.

OK. Is anything written up about this?

No, maybe we should add something about this in the arm BSP section of the user
manual.

That would be helpful.

For example is allocating variables
automatic or can I control allocation to it?

You just have to place a function or variable with the section attribute into
these sections:

bsps/arm/include/bsp/linker-symbols.h:#define BSP_FAST_TEXT_SECTION \
bsps/arm/include/bsp/linker-symbols.h- RTEMS_SECTION(".bsp_fast_text")

bsps/arm/include/bsp/linker-symbols.h:#define BSP_FAST_DATA_SECTION \
bsps/arm/include/bsp/linker-symbols.h- RTEMS_SECTION(".bsp_fast_data")

I think would be good to document otherwise no one will know it exists or how it
can be used.

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