Hi Andreas, On Fri, Oct 19, 2018 at 03:53:02PM +0000, Andreas Puhm wrote: > Hello, > > I hope the following information is descriptive enough. > If this is no the case, I will provide further details. > > -------------------------------------------------------------------- > Full description: > The altera_cvp probe function only checks, > if the Altera/Intel PCI device configuration space contains a vendor specific entry (VSEC Capability Header 0x000b) at offset 0x200. > But the probe function does not verify, if the PCI device (and further the FPGA), > for which it has been called, actually supports the Configure-via-Protocol feature. > > The PCI device (FPGA) can explicitly disable the Configur-via-Protocol (CvP) feature by setting the CVP_EN bit, index 20 of CVP_STATUS register, to '0'. > As the altera_cvp probe function does not check this it registers the device in any way. > At this point, the altera_cvp module cannot be used to program this device via CvP. > In addition no other module can use the device, as it is still registered by altera_cvp. > > Keywords: altera_cvp module, PCI, Configure-via-Protocol > > Kernel version: problem occured with v4.15, should occur from 4.14+ > > Instructions to reproduce: > Proper hardware is necessary to reproduce this, i.e., FPGA with instantiated Altera/Intel PCIe IP Core with disabled CvP feature. > > Workaround: > It is possible to circumvent this problem by manually unloading or blacklisting the altera_cvp module. > > Suggested Patch: > This patch was successfully build and tested for 4.15 and 4.18 > > Subject: [PATCH] register device only, if it supports CvP operation Could you make this: 'fpga: altera_cvp: Conditionalize registration' or something along those lines? > > This patch is based on: git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tag/?h=v4.18 Put some of the extensive description you made above in the git commit message, please, such that future us will know why the change was made :) Thanks for your patch, Moritz
