H7 SystemInit contains line with no effect

[JojoS]

I had debugging problems with a H7 target, and by stepping thru the boot process I found the following line in SystemInit():

/*
   * Disable the FMC bank1 (enabled after reset).
   * This, prevents CPU speculation access on this bank which blocks the use of FMC during
   * 24us. During this time the others FMC master (such as LTDC) cannot use it!
   */
  FMC_Bank1_R->BTCR[0] = 0x000030D2;

At this stage of the boot process, the FMC power is not enabled, and thus reading or writing the register has no effect. Am I overseeing something or is this line for confusion?

[SofLit · Accepted solution]

Hello @JojoS ,

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@JojoS wrote:

At this stage of the boot process, the FMC power is not enabled, 

---

You mean FMC clock not the power but your comment makes sense as the FMC clock is enabled in SystemInit_ExtMemCtl(), just after. 

I will escalate this remark internally and get back to you as soon as I have an answer. Internal ticket number for follow up: 196021

[Tesla DeLorean]

>> Am I overseeing something or is this line for confusion?

Are you easily confused, is it a problem?

Probably there due to the generic way in which ST builds these thing, and perhaps salient to one particular case.

Perhaps so when built as a secondary application the loader has already started the clocks, external memories, etc prior to getting here.

Which file/project was this lifted from? An EVAL / DISCO board?

The SystemInit() in ARM's model would be used to bring up the whole board and memories so startup.s code can copy statics, etc.

[JojoS]

Thanks, of corse it as a minor issue as it should have no affect. But it would be clearer if it is conditionally inserted. 

[SofLit]

FYI,

Issue confirmed and will be fixed.