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SubjectRe: [PATCH] PCI: designware: fix asynchronous external abort in keystone PCIe h/w
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On 01/10/2017 06:06 PM, Bjorn Helgaas wrote:
> 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@synopsys.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@ti.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@ti.com>
> Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> CC: stable@vger.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);
>
Thanks Bjorn! Looks good.

--
Murali Karicheri
Linux Kernel, Keystone

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