[RTEMS Project] #4159: Document the fast text and data sections in the user manual

[RTEMS trac]

#4159: Document the fast text and data sections in the user manual
------------------------------+-----------------------------
  Reporter:  Sebastian Huber  |      Owner:  Sebastian Huber
      Type:  enhancement      |     Status:  assigned
  Priority:  normal           |  Milestone:  6.1
 Component:  doc              |    Version:  6
  Severity:  normal           |   Keywords:
Blocked By:                   |   Blocking:
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 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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Ticket URL: <http://devel.rtems.org/ticket/4159>
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