Re: [PATCH v1 4/4] PCI: brcmstb: add shutdown call to driver

Florian Fainelli
2021-05-26T17:03:56Z

On 5/25/21 2:18 PM, Bjorn Helgaas wrote:
> Capitalize "Add" in the subject.
>
> On Tue, Apr 27, 2021 at 01:51:39PM -0400, Jim Quinlan wrote:
>> The shutdown() call is similar to the remove() call except the former does
>> not need to invoke pci_{stop,remove}_root_bus(), and besides, errors occur
>> if it does.
>
> This doesn't explain why shutdown() is necessary. "errors occur"
> might be a hint, except that AFAICT, many similar drivers do invoke
> pci_stop_root_bus() and pci_remove_root_bus() (several of them while
> holding pci_lock_rescan_remove()), without implementing .shutdown().

We have to implement .shutdown() in order to meet a certain power budget
while the chip is being put into S5 (soft off) state and still support
Wake-on-WLAN, for our latest chips this translates into roughly 200mW of
power savings at the wall. We could probably add a word or two in a v2
that indicates this is done for power savings.

As far as the crash goes, if we call brcm_pcie_remove() directly from
brcm_pcie_shutdown() we see the following (this is in 5.4, but I have no
reason to believe mainline is different):

# lspci
0001:00:00.0 PCI bridge: Broadcom Inc. and subsidiaries Device 7216 (rev 10)
0001:01:00.0 Network controller: Qualcomm Atheros AR9285 Wireless
Network Adapter (PCI-Express) (rev 01)
# reboot -f
[ 8.465111] ------------[ cut here ]------------
[ 8.469771] pcieport 0001:00:00.0: disabling already-disabled device
[ 8.469817] WARNING: CPU: 3 PID: 1656 at drivers/pci/pci.c:1945
pci_disable_device+0x78/0xd0
[ 8.484631] Modules linked in:
[ 8.487695] CPU: 3 PID: 1656 Comm: reboot Not tainted
5.4.120-1.1pre-g231f2cfa989a #4
[ 8.495537] Hardware name: BCX972160DV (DT)
[ 8.499728] pstate: 60000005 (nZCv daif -PAN -UAO)
[ 8.504527] pc : pci_disable_device+0x78/0xd0
[ 8.508891] lr : pci_disable_device+0x78/0xd0
[ 8.513254] sp : ffffffc014d33aa0
[ 8.516572] x29: ffffffc014d33aa0 x28: ffffff809deac800
[ 8.521894] x27: ffffff809e23a5b0 x26: ffffff809e23a490
[ 8.527214] x25: 0000000000000000 x24: ffffff809cf9f000
[ 8.532535] x23: ffffffc011d13090 x22: 0000000000000000
[ 8.537856] x21: 0000000000000000 x20: ffffff809cf9f0b0
[ 8.543175] x19: ffffff809cf9f000 x18: 000000000000000a
[ 8.548495] x17: 0000000000000000 x16: 0000000000000000
[ 8.553816] x15: 00000000000718d7 x14: 0720072007200720
[ 8.559138] x13: 0720072007200720 x12: 0720072007200720
[ 8.564458] x11: 0720072007200720 x10: 0720072007200720
[ 8.569777] x9 : 0720072007200720 x8 : 656c62617369642d
[ 8.575098] x7 : 79646165726c6120 x6 : ffffffc011dc3630
[ 8.580417] x5 : 0000000000000038 x4 : 0000000000000000
[ 8.585737] x3 : 0000000000000000 x2 : 0000000000000000
[ 8.591058] x1 : 73b2329426297100 x0 : 0000000000000000
[ 8.596379] Call trace:
[ 8.598832] pci_disable_device+0x78/0xd0
[ 8.602852] pcie_port_device_remove+0x3c/0x48
[ 8.607304] pcie_portdrv_remove+0x5c/0x8c
[ 8.611408] pci_device_remove+0x98/0xe8
[ 8.615341] device_release_driver_internal+0xb0/0x188
[ 8.620487] device_release_driver+0x28/0x34
[ 8.624765] pci_stop_bus_device+0x40/0xa8
[ 8.628867] pci_stop_root_bus+0x58/0x64
[ 8.632797] brcm_pcie_remove+0x24/0x70
[ 8.636640] brcm_pcie_shutdown+0x20/0x2c
[ 8.640655] platform_drv_shutdown+0x2c/0x38
[ 8.644934] device_shutdown+0x16c/0x1e0
[ 8.648865] kernel_restart_prepare+0x44/0x50
[ 8.653229] kernel_restart+0x20/0x68
[ 8.656896] __do_sys_reboot+0x158/0x200
[ 8.660816] __arm64_sys_reboot+0x2c/0x38
[ 8.664833] el0_svc_common.constprop.2+0xe8/0x168
[ 8.669631] el0_svc_handler+0x34/0x80
[ 8.673388] el0_svc+0x8/0x1fc
[ 8.676447] ---[ end trace 778d7966a5ef8213 ]---
[ 8.694539] pci_bus 0001:01: busn_res: [bus 01] is released
[ 8.700279] pci_bus 0001:00: busn_res: [bus 00-ff] is released
[ 8.710206] reboot: Restarting system

>
> It is ... unfortunate that there's such a variety of implementations
> here. I don't believe these driver differences are all necessary
> consequences of hardware differences.

Yes, that is a bit unfortunate, Rob's idea to consolidate the
implementation sounds good and we can definitively test that.

>
>> Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
>> ---
>> drivers/pci/controller/pcie-brcmstb.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
>> index d3af8d84f0d6..a1fe1a2ada48 100644
>> --- a/drivers/pci/controller/pcie-brcmstb.c
>> +++ b/drivers/pci/controller/pcie-brcmstb.c
>> @@ -1340,6 +1340,15 @@ static int brcm_pcie_remove(struct platform_device *pdev)
>> return 0;
>> }
>>
>> +static void brcm_pcie_shutdown(struct platform_device *pdev)
>> +{
>> + struct brcm_pcie *pcie = platform_get_drvdata(pdev);
>> +
>> + if (pcie->has_err_report)
>> + brcm_unregister_die_notifiers(pcie);
>> + __brcm_pcie_remove(pcie);
>> +}
>> +
>> static const struct of_device_id brcm_pcie_match[] = {
>> { .compatible = "brcm,bcm2711-pcie", .data = &bcm2711_cfg },
>> { .compatible = "brcm,bcm4908-pcie", .data = &bcm4908_cfg },
>> @@ -1460,6 +1469,7 @@ static const struct dev_pm_ops brcm_pcie_pm_ops = {
>> static struct platform_driver brcm_pcie_driver = {
>> .probe = brcm_pcie_probe,
>> .remove = brcm_pcie_remove,
>> + .shutdown = brcm_pcie_shutdown,
>> .driver = {
>> .name = "brcm-pcie",
>> .of_match_table = brcm_pcie_match,
>> --
>> 2.17.1
>>

--
Florian