On Wednesday 10 February 2021 13:59:41 Stefan Chulski wrote: > > > (sending this e-mail again because previously I sent it to Thomas' old > > > e-mail address at free-electrons) > > > > Thanks. Turns out I still receive e-mail sent to @free-electrons.com, so I had > > seen your previous e-mail but didn't had the chance to reply. > > > > > we have enountered an issue with pci-mvebu driver and would like your > > > opinion, since you are the author of commit > > > https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pu > > > b_scm_linux_kernel_git_torvalds_linux.git_commit_-3Fid- > > 3Df4ac99011e542 > > > > > d06ea2bda10063502583c6d7991&d=DwIFaQ&c=nKjWec2b6R0mOyPaz7xtfQ& > > r=DDQ3dK > > > wkTIxKAl6_Bs7GMx4zhJArrXKN2mDMOXGh7lg&m=lENmudbu2hlK44mVm- > > e8bgdi9Rm2AC > > > DXN8QY0frgcuY&s=7109I- > > xvpx1wW532pxvk1W8s_XeG77VQf2iP7QzhEao&e= > > > > > > After upgrading to new version of U-Boot on a Armada XP / 38x device, > > > some WiFi cards stopped working in kernel. Ath10k driver, for example, > > > could not load firmware into the card. > > > > > > We discovered that the issue is caused by U-Boot: > > > - when U-Boot's pci_mvebu driver was converted to driver model API, > > > U-Boot started to configure PCIe registers not only for the newtork > > > adapter, but also for the Marvell Memory Controller (that you are > > > mentioning in your commit). > > > - Since pci-mvebu driver in Linux is ignoring the Marvell Memory > > > Controller device, and U-Boot configures its registers (BARs and what > > > not), after kernel boots, the registers of this device are > > > incompatible with kernel, or something, and this causes problems for > > > the real PCIe device. > > > - Stefan Roese has temporarily solved this issue with U-Boot commit > > > https://urldefense.proofpoint.com/v2/url?u=https- > > 3A__gitlab.denx.de_u-2Dboot_custodians_u-2Dboot-2Dmarvell_- > > 2D_commit_6a2fa284aee2981be2c7661b3757ce112de8d528&d=DwIFaQ&c=n > > KjWec2b6R0mOyPaz7xtfQ&r=DDQ3dKwkTIxKAl6_Bs7GMx4zhJArrXKN2mDM > > OXGh7lg&m=lENmudbu2hlK44mVm- > > e8bgdi9Rm2ACDXN8QY0frgcuY&s=B0eKBkblEygPGYvKDdMuwzzYhDg5Jlh_Q4 > > eXHlIL-oc&e= > > > which basically just masks the Memory Controller's existence. > > > > > > - in Linux commit f4ac99011e54 ("pci: mvebu: no longer fake the slot > > > location of downstream devices") you mention that: > > > > > > * On slot 0, a "Marvell Memory controller", identical on all PCIe > > > interfaces, and which isn't useful when the Marvell SoC is the PCIe > > > root complex (i.e, the normal case when we run Linux on the Marvell > > > SoC). > > > > > > What we are wondering is: > > > - what does the Marvell Memory controller really do? Can it be used to > > > configure something? It clearly does something, because if it is > > > configured in U-Boot somehow but not in kernel, problems can occur. > > > - is the best solution really just to ignore this device? > > > - should U-Boot also start doing what commit f4ac99011e54 does? I.e. > > > to make sure that the real device is in slot 0, and Marvell Memory > > > Controller in slot 1. > > > - why is Linux ignoring this device? It isn't even listed in lspci > > > output. > > > > To be honest, I don't have much details about what this device does, and my > > memory is unclear on whether I really ever had any details. I vaguely > > remember that this is a device that made sense when the Marvell PCIe > > controller is used as an endpoint, and in such a situation this device also the > > root complex to "see" the physical memory of the Marvell SoC. And > > therefore in a situation where the Marvell PCIe controller is the root > > complex, seeing this device didn't make sense. > > > > In addition, I /think/ it was causing problems with the MBus windows > > allocation. Indeed, if this device is visible, then we will try to allocate MBus > > windows for its different BARs, and those windows are in limited number. > > > > I know this isn't a very helpful answer, but the documentation on this is > > pretty much nonexistent, and I don't remember ever having very solid and > > convincing answers. > > > > I've added in Cc Stefan Chulski, from Marvell, who has recently posted > > patches on the PPv2 driver. I don't know if he will have details about PCIe, > > but perhaps he will be able to ask internally at Marvell. > > > > Best regards, > > I not familiar with Armada XP PCIe. But I can check internally at Marvell. > > Best Regards, > Stefan. > Stefan: If you get any information internally in Marvell, please let us know! Bjorn: What do you think, should Linux kernel completely hide some PCIe devices from /sys hierarchy and also from 'lspci' output? Or should kernel preserve even non-functional / unknown PCIe devices visible in 'lspci' output?
