target/linux/mvebu/patches-5.4/408-PCI-aardvark-Don-t-touch-PCIe-registers-if-no-card-c.patch

   1 From 70e380250c3621c55ff218cbaf2272830d9dbb1d Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Pali=20Roh=C3=A1r?= <pali@kernel.org>
   3 Date: Thu, 2 Jul 2020 10:30:36 +0200
   4 Subject: [PATCH] PCI: aardvark: Don't touch PCIe registers if no card
   5  connected
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 When there is no PCIe card connected and advk_pcie_rd_conf() or
  11 advk_pcie_wr_conf() is called for PCI bus which doesn't belong to emulated
  12 root bridge, the aardvark driver throws the following error message:
  13
  14   advk-pcie d0070000.pcie: config read/write timed out
  15
  16 Obviously accessing PCIe registers of disconnected card is not possible.
  17
  18 Extend check in advk_pcie_valid_device() function for validating
  19 availability of PCIe bus. If PCIe link is down, then the device is marked
  20 as Not Found and the driver does not try to access these registers.
  21
  22 This is just an optimization to prevent accessing PCIe registers when card
  23 is disconnected. Trying to access PCIe registers of disconnected card does
  24 not cause any crash, kernel just needs to wait for a timeout. So if card
  25 disappear immediately after checking for PCIe link (before accessing PCIe
  26 registers), it does not cause any problems.
  27
  28 Link: https://lore.kernel.org/r/20200702083036.12230-1-pali@kernel.org
  29 Signed-off-by: Pali Rohár <pali@kernel.org>
  30 Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
  31 ---
  32  drivers/pci/controller/pci-aardvark.c | 7 +++++++
  33  1 file changed, 7 insertions(+)
  34
  35 --- a/drivers/pci/controller/pci-aardvark.c
  36 +++ b/drivers/pci/controller/pci-aardvark.c
  37 @@ -639,6 +639,13 @@ static bool advk_pcie_valid_device(struc
  38         if ((bus->number == pcie->root_bus_nr) && PCI_SLOT(devfn) != 0)
  39                 return false;
  40
  41 +       /*
  42 +        * If the link goes down after we check for link-up, nothing bad
  43 +        * happens but the config access times out.
  44 +        */
  45 +       if (bus->number != pcie->root_bus_nr && !advk_pcie_link_up(pcie))
  46 +               return false;
  47 +
  48         return true;
  49  }
  50