Hi Gavin,
On Wed, Dec 10, 2014 at 11:03 PM, Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx> wrote:
> When unbinding PCI device mlx4 from its driver, the PCI device is
> disabled by pci_disable_device() and the BARs (IO and memory) should
> be disabled at the point. However, the memory BARs are still active
> after the mlx4_core driver is unloaded as following logs show.
>
> # lspci -vv -s 0003:0f:00.0
> 0003:0f:00.0 Network controller: Mellanox Technologies \
> MT27500 Family [ConnectX-3]
> Subsystem: Mellanox Technologies Device 0061
> Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- \
> ParErr+ Stepping- SERR+ FastB2B- DisINTx+
> :
> Kernel driver in use: mlx4_core
> # echo 0003:0f:00.0 > /sys/bus/pci/drivers/mlx4_core/unbind
> # lspci -vv -s 0003:0f:00.0
> 0003:0f:00.0 Network controller: Mellanox Technologies \
> MT27500 Family [ConnectX-3]
> Subsystem: Mellanox Technologies Device 0061
> Control: I/O- Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- \
> ParErr+ Stepping- SERR+ FastB2B- DisINTx-
>
> The patch turns off all BARs (IO and memory) in do_pci_disable_device().
>
> Signed-off-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/pci/pci.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 625a4ac..8d2924b 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1496,12 +1496,14 @@ void __weak pcibios_penalize_isa_irq(int irq, int active) {}
>
> static void do_pci_disable_device(struct pci_dev *dev)
> {
> - u16 pci_command;
> + u16 cmd, flags = (PCI_COMMAND_IO |
> + PCI_COMMAND_MEMORY |
> + PCI_COMMAND_MASTER);
>
> - pci_read_config_word(dev, PCI_COMMAND, &pci_command);
> - if (pci_command & PCI_COMMAND_MASTER) {
> - pci_command &= ~PCI_COMMAND_MASTER;
> - pci_write_config_word(dev, PCI_COMMAND, pci_command);
> + pci_read_config_word(dev, PCI_COMMAND, &cmd);
> + if (cmd & flags) {
> + cmd &= ~flags;
> + pci_write_config_word(dev, PCI_COMMAND, cmd);
Does this fix an actual problem? If so, I'd like to see details about
what the problem is.
I'm a bit concerned about turning off IO/MEMORY/MASTER unconditionally
because we have code that is a bit careful to avoid that in some
cases. Search for "mmio_always_on" and see commit 253d2e549818 ("PCI:
disable mmio during bar sizing").
So if this patch fixes a problem, all well and good, but we do need to
make sure we don't introduce another problem at the same time.
Bjorn
> }
>
> pcibios_disable_device(dev);
> --
> 1.8.3.2
>
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