[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v3] docs: fusa: Add Assumption of Use (AoU)
From: Michal Orzel <michal.orzel@xxxxxxx> AoU are the assumptions that Xen relies on other components (eg platform platform, domains) to fulfill its requirements. In our case, platform means a combination of hardware, firmware and bootloader. We have defined AoU in the intro.rst and added AoU for the generic timer. Also, fixed a requirement to denote that Xen shall **not** expose the system counter frequency via the "clock-frequency" device tree property. The reason being the device tree documentation strongly discourages the use of this peoperty. Further if the "clock-frequency" is exposed, then it overrides the value programmed in the CNTFRQ_EL0 register. So, the frequency shall be exposed via the CNTFRQ_EL0 register only and consequently there is an assumption on the platform to program the register correctly. Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx> Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx> --- Changes from :- v1 - 1. Removed the part of requirement which states that Xen exposes the frequency of the system timer by reading the "clock-frequency" property. 2. Added a rationale for AoU. 3. Reworded the AoU. v2 - 1. Reworded the commit message. Added R-b. .../reqs/design-reqs/arm64/generic-timer.rst | 24 ++++++++++++++++++- docs/fusa/reqs/intro.rst | 10 ++++++++ 2 files changed, 33 insertions(+), 1 deletion(-) diff --git a/docs/fusa/reqs/design-reqs/arm64/generic-timer.rst b/docs/fusa/reqs/design-reqs/arm64/generic-timer.rst index f2a0cd7fb8..86d84a3c40 100644 --- a/docs/fusa/reqs/design-reqs/arm64/generic-timer.rst +++ b/docs/fusa/reqs/design-reqs/arm64/generic-timer.rst @@ -30,7 +30,7 @@ Read system counter frequency Description: Xen shall expose the frequency of the system counter to the domains in -CNTFRQ_EL0 register and/or domain device tree's "clock-frequency" property. +CNTFRQ_EL0 register. Rationale: @@ -116,6 +116,28 @@ Rationale: Comments: +Covers: + - `XenProd~emulated_timer~1` + +Assumption of Use on the Platform +================================= + +Expose system timer frequency via register +------------------------------------------ + +`XenSwdgn~arm64_generic_timer_pf_program_cntfrq_el0~1` + +Description: +Underlying platform shall program CNTFRQ_EL0 register with the value of system +timer frequency. + +Rationale: +Xen reads the CNTFRQ_EL0 register to get the value of system timer frequency. +While there is a provision to get this value by reading the "clock-frequency" +dt property [2], the use of this property is strongly discouraged. + +Comments: + Covers: - `XenProd~emulated_timer~1` diff --git a/docs/fusa/reqs/intro.rst b/docs/fusa/reqs/intro.rst index 245a219ff2..aa85ff821c 100644 --- a/docs/fusa/reqs/intro.rst +++ b/docs/fusa/reqs/intro.rst @@ -38,6 +38,16 @@ The requirements are linked using OpenFastTrace OpenFastTrace parses through the requirements and generates a traceability report. +Assumption of Use +================= + +To fulfill one or more design requirements, there may be underlying assumptions +on one or more components that Xen interacts with directly or indirectly. For +eg, there may be assumptions on the underlying platform (hardware + firmware + +bootloader) to set certain registers, etc. The important thing here is that +anyone who validates these requirements, need to consider the assumption on the +other components. + The following is the skeleton for a requirement. Title of the requirement -- 2.25.1
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