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Date: Tue, 10 Jan 2017 17:06:29 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Murali Karicheri <m-karicheri2@...com>
Cc: jingoohan1@...il.com, Joao.Pinto@...opsys.com, bhelgaas@...gle.com,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: designware: fix asynchronous external abort in
keystone PCIe h/w
On Tue, Jan 10, 2017 at 12:18:29PM -0500, Murali Karicheri wrote:
> On 01/10/2017 10:12 AM, Bjorn Helgaas wrote:
> > Hi Murali,
> >
> > On Wed, Jan 04, 2017 at 02:32:30PM -0500, Murali Karicheri wrote:
> >> Recent fixes for iATU unroll support introduced a bug that causes
> >> asynchronous external abort in Keystone PCIe h/w which doesn't have
> >> ATU port and the corresponding register. So the check should be moved
> >> below where dw_pcie_prog_outbound_atu() is called to avoid that
> >> being called on keystine PCIe h/w.
> >>
> >> Here is the backtrace
> >>
> >> [ 0.771174] OF: PCI: MEM 0x60000000..0x6fffffff -> 0x60000000
> >> [ 0.778118] Unhandled fault: asynchronous external abort (0x1211) at 0x00000000
> >> [ 0.785548] pgd = c0003000
> >> [ 0.788347] [00000000] *pgd=80000800004003, *pmd=00000000
> >> [ 0.793864] Internal error: : 1211 [#1] PREEMPT SMP ARM
> >> [ 0.799197] Modules linked in:
> >> [ 0.802351] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.9.0-00009-g6ff59d2-dirty #7
> >> [ 0.810130] Hardware name: Keystone
> >> [ 0.813717] task: eb878000 task.stack: eb866000
> >> [ 0.818356] PC is at dw_pcie_setup_rc+0x24/0x380
> >> [ 0.823083] LR is at ks_pcie_host_init+0x10/0x170
> >>
> >> Fixes: 416379f9ebde ("PCI: designware: Check for iATU unroll support after initializing host")
> >
> > I tentatively applied this to for-linus for v4.10, with a stable tag
> > for v4.9+.
> >
>
> Ok Thanks!
>
> > The patch itself mostly makes sense in terms of the code: we only use
> > iatu_unroll_enabled in dw_pcie_prog_outbound_atu(). We only call that
> > when "!pp->ops->rd_other_conf" or "!pp->ops->wr_other_conf".
> >
> > So it makes sense that we only need to initialize iatu_unroll_enabled
> > in those cases. But the current patch only initializes it if
> > "!pp->ops->rd_other_conf".
> >
>
> I think the code before also should have checked for both
> if ((!pp->ops->rd_other_conf) && (!pp->ops->wr_other_conf))
>
> The assumption was if rd_other_conf is Null, the platform provides
> both rd_other_conf and wr_other_conf. I see I have added this API
> to support Keystone and the above assumption is true so far.
> It make sense to fix it if you agree.
>
> > If we had "pp->ops->rd_other_conf && !pp->ops->wr_other_conf", we
> > would use iatu_unroll_enabled uninitialized in the
> > dw_pcie_wr_other_conf() path. I suppose that's an invalid
>
> Yes. So we need to fix the above to make the code correct instead
> of leaving it exposed.
>
> > configuration, but it'd be better if we didn't have to rely on the
> > host drivers to avoid that configuration.
>
> You mean to introduce the check in the designware core code above
> right?
We *could* make the code look like:
if (!pp->ops->rd_other_conf || !pp->ops->rd_other_conf)
pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
but that seems a little clunky and the connection between ATU and the
->*_other_conf() pointers is slightly obscure. I guess it just ends
up being more detailed than I personally really want to worry about,
so I'm fine with leaving it as-is for now.
> > It's not obvious how this is connected to 416379f9ebde, though. It
> > *looks* like we call dw_pcie_iatu_unroll_enabled() on Keystone both
> > before and after that commit, so it seems like the external abort
> > should have happened even before it.
> >
>
> You are right. The problem was introduced by
>
> commit a0601a47053714eecec726aea5ebcd829f817497
> Author: Joao Pinto <Joao.Pinto@...opsys.com>
> Date: Wed Aug 10 11:02:39 2016 +0100
>
> PCI: designware: Add iATU Unroll feature
>
> which is fixed by commit 416379f9ebde and is again fixed by my
> commit. So probably I should have added both commits in
> my description.
I added that. The reason I wanted the correct "Fixes" information is
to figure out which stable kernels need this fix. In this case, both:
a0601a470537 ("PCI: designware: Add iATU Unroll feature") and
416379f9ebde ("PCI: designware: Check for iATU unroll support after
initializing host")
appeared in v4.9, so it doesn't change anything as far as the stable
tag is concerned.
The below is what I have on my for-linus branch:
commit 6fdb996a55684016de1ce639b9316b7092fde95f
Author: Murali Karicheri <m-karicheri2@...com>
Date: Wed Jan 4 14:32:30 2017 -0500
PCI: designware: Check for iATU unroll only on platforms that use ATU
Previously we checked for iATU unroll support by reading PCIE_ATU_VIEWPORT
even on platforms, e.g., Keystone, that do not have ATU ports. This can
cause bad behavior such as asynchronous external aborts:
OF: PCI: MEM 0x60000000..0x6fffffff -> 0x60000000
Unhandled fault: asynchronous external abort (0x1211) at 0x00000000
pgd = c0003000
[00000000] *pgd=80000800004003, *pmd=00000000
Internal error: : 1211 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.9.0-00009-g6ff59d2-dirty #7
Hardware name: Keystone
task: eb878000 task.stack: eb866000
PC is at dw_pcie_setup_rc+0x24/0x380
LR is at ks_pcie_host_init+0x10/0x170
Move the dw_pcie_iatu_unroll_enabled() check so we only call it on
platforms that do not use the ATU. These platforms supply their own
->rd_other_conf() and ->wr_other_conf() methods.
[bhelgaas: changelog]
Fixes: a0601a470537 ("PCI: designware: Add iATU Unroll feature")
Fixes: 416379f9ebde ("PCI: designware: Check for iATU unroll support after initializing host")
Tested-by: Kishon Vijay Abraham I <kishon@...com>
Signed-off-by: Murali Karicheri <m-karicheri2@...com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
CC: stable@...r.kernel.org # v4.9+
diff --git a/drivers/pci/host/pcie-designware.c b/drivers/pci/host/pcie-designware.c
index bed19994c1e9..af8f6e92e885 100644
--- a/drivers/pci/host/pcie-designware.c
+++ b/drivers/pci/host/pcie-designware.c
@@ -807,11 +807,6 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
{
u32 val;
- /* get iATU unroll support */
- pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
- dev_dbg(pp->dev, "iATU unroll: %s\n",
- pp->iatu_unroll_enabled ? "enabled" : "disabled");
-
/* set the number of lanes */
val = dw_pcie_readl_rc(pp, PCIE_PORT_LINK_CONTROL);
val &= ~PORT_LINK_MODE_MASK;
@@ -882,6 +877,11 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
* we should not program the ATU here.
*/
if (!pp->ops->rd_other_conf) {
+ /* get iATU unroll support */
+ pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
+ dev_dbg(pp->dev, "iATU unroll: %s\n",
+ pp->iatu_unroll_enabled ? "enabled" : "disabled");
+
dw_pcie_prog_outbound_atu(pp, PCIE_ATU_REGION_INDEX0,
PCIE_ATU_TYPE_MEM, pp->mem_base,
pp->mem_bus_addr, pp->mem_size);
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