SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Fundamental hardware reset - This reset impacts all non-sticky PCIe core bits. It is automatically triggered:
All (sticky and non-sticky bits) of the PCIe controller core are reset upon fundamental hardware reset assertion because of Vaux not implemented. Hereby all PCIe core registers have to be re-initialized from scratch after a PCIe fundamental reset.
Hardware fundamental reset operation: The hardware fundamental reset is an input to the PCIe core, to be controlled by the local PCIe software driver. Its impact is conditional: a fundamental reset clears the entire controller (including the PCIe_PHY part), with the following exceptions:
The fundamental reset is applied to PCIe core in the following two cases :
The TYPE value ("EP", "legacy EP" or "RC") has to be read back by software until desired type-value is seen. This insures that the fundamental reset triggered by "TYPE" change has completed successfully. The user software must not change the PCIECTRL_TI_CONF_DEVICE_TYPE[3:0] TYPE register value during PCIe core operation.
The fundamental hardware reset does not impact the PCIECTRL_TI_CONF_DEVICE_TYPE[3:0] TYPE (RC/EP) bitfield and the remaining TI wrapper configuration registers (PCIe_SS_TI_CONF). These can be reset only by a PCIe main reset input assertion.
PCIe link-down reset condition - When the PCIe link has gone down and goes up again, namely transitions from D3cold/L3 back to D0, the PCIe core auto-applies this internal fundamental reset and reports it on IRQ event (PCIECTRL_TI_CONF_IRQSTATUS_MAIN[11] LINK_REQ_RST) after link-up.
PCIe hot-reset condition - As defined by the PCIe standard: reset condition propagated in-band (over the PCIe wire) from an upstream port to a downstream port, using the TS1 and TS2 OS (see the PCI Express Base 3.0 Specification, revision 1.0). Requires the link to be already powered and up. The hot reset causes the link to go down and up again, causing a link-down reset condition, and as such is a fundamental reset.
The hot reset sequence can be tracked in the LTSSM by the transition to "hot reset" state, then on to "detect" and the rest of the link-up sequence.
PCIe soft reset condition - As defined by the PCIe standard: When the D-state of a device is changed from D3hot to D0 by software, namely by the RC doing a remote CFG write to the EP (EP) PM_CSR [1:0] PWR_STATE register, the EP device reacts depending on its DIF CS (local) setting of the no-soft-reset (NSR) bit (EP) PM_CSR [3] NSR:
The soft reset is a hot reset. The soft reset is not a fundamental reset; that means that it does not reset the PHY, only the programming registers.