On Tue, Aug 29, 2017 at 12:47 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > On Thu, Aug 24, 2017 at 10:34:25AM +0530, Oza Pawandeep wrote: >> PCIe spec r3.1, sec 2.3.2 >> If CRS software visibility is not enabled, the RC must reissue the >> config request as a new request. >> >> - If CRS software visibility is enabled, >> - for a config read of Vendor ID, the RC must return 0x0001 data >> - for all other config reads/writes, the RC must reissue the >> request >> >> iproc PCIe Controller spec: >> 4.7.3.3. Retry Status On Configuration Cycle >> Endpoints are allowed to generate retry status on configuration >> cycles. In this case, the RC needs to re-issue the request. The IP >> does not handle this because the number of configuration cycles needed >> will probably be less than the total number of non-posted operations >> needed. >> >> When a retry status is received on the User RX interface for a >> configuration request that was sent on the User TX interface, >> it will be indicated with a completion with the CMPL_STATUS field set >> to 2=CRS, and the user will have to find the address and data values >> and send a new transaction on the User TX interface. >> When the internal configuration space returns a retry status during a >> configuration cycle (user_cscfg = 1) on the Command/Status interface, >> the pcie_cscrs will assert with the pcie_csack signal to indicate the >> CRS status. >> When the CRS Software Visibility Enable register in the Root Control >> register is enabled, the IP will return the data value to 0x0001 for >> the Vendor ID value and 0xffff (all 1’s) for the rest of the data in >> the request for reads of offset 0 that return with CRS status. This >> is true for both the User RX Interface and for the Command/Status >> interface. When CRS Software Visibility is enabled, the CMPL_STATUS >> field of the completion on the User RX Interface will not be 2=CRS and >> the pcie_cscrs signal will not assert on the Command/Status interface. >> >> Per PCIe r3.1, sec 2.3.2, config requests that receive completions >> with Configuration Request Retry Status (CRS) should be reissued by >> the hardware except reads of the Vendor ID when CRS Software >> Visibility is enabled. >> >> This hardware never reissues configuration requests when it receives >> CRS completions. >> Note that, neither PCIe host bridge nor PCIe core re-issues the >> request for any configuration offset. >> >> For config reads, this hardware returns CFG_RETRY_STATUS data when >> it receives a CRS completion for a config read, regardless of the >> address of the read or the CRS Software Visibility Enable bit. > > I can't remember how Stingray handles the CRS Software Visibility Enable > bit. Is it a read-only zero? Is it writable? Does the hardware look at > it all (I think not)? HW doesnt look it at all, it is "dont care" bit. Regards, Oza. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
