[RFC PATCH] PCI: rockchip: fix system hang up if activate CONFIG_DEBUG_SHIRQ

[Shawn Lin]

Hi Heiko

On 2017/8/10 17:27, Heiko Stuebner wrote:
> Hi Shawn,
> 
> Am Donnerstag, 10. August 2017, 16:21:13 CEST schrieb Shawn Lin:
>> With CONFIG_DEBUG_SHIRQ enabled, the irq tear down routine
>> would still access the irq handler registed as a shard irq.
>> Per the comment within the function of __free_irq, it says
>> "It's a shared IRQ -- the driver ought to be prepared for
>> an IRQ event to happen even now it's being freed". However
>> when failing to probe the driver, it may disable the clock
>> for accessing the register and the following check for shared
>> irq state would call the irq handler which accesses the register
>> w/o the clk enabled. That will hang the system forever.
> 
> The key point would be to fix the ordering. So you could also just use
> devm_add_action to move the clock-disabling into a callback that
> gets run at the appropriate time, as devm does the shutdown in the
> exact opposite order this should fix your problem.
> 
> So until all clocks could be enabled, you would disable them manually
> and after that rely on the devm_action to fire at the appropriate time.
> 
> ret = clk_prepare_enable(clk1);
> if (ret < 0 )
> 	return ret;
> 
> ret = clk_prepare_enable(clk2);
> if (ret < 0) {
> 	clk_disable_unprepare(clk1);
> 	return ret;
> }
> 
> devm_add_action_or_reset(dev, rk_pcie_disable_clocks);
> 

That seems great! I will respin v2 for that.

> The rockchip crypto driver [0] shows how this could be done.
> 
> 
> Heiko
> 
> [0] http://elixir.free-electrons.com/linux/latest/source/drivers/crypto/rockchip/rk3288_crypto.c#L307
> 
>>
>> With adding some dump_stack we could see how that happened.
>>
>> calling  rockchip_pcie_driver_init+0x0/0x28 @ 1
>> rockchip-pcie f8000000.pcie: no vpcie3v3 regulator found
>> rockchip-pcie f8000000.pcie: no vpcie1v8 regulator found
>> rockchip-pcie f8000000.pcie: no vpcie0v9 regulator found
>> rockchip-pcie f8000000.pcie: PCIe link training gen1 timeout!
>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted
>> 4.13.0-rc3-next-20170807-ARCH+ #189
>> Hardware name: Firefly-RK3399 Board (DT)
>> Call trace:
>> [<ffff000008089bf0>] dump_backtrace+0x0/0x250
>> [<ffff000008089eb0>] show_stack+0x20/0x28
>> [<ffff000008c3313c>] dump_stack+0x90/0xb0
>> [<ffff000008632ad4>] rockchip_pcie_read.isra.11+0x54/0x58
>> [<ffff0000086334fc>] rockchip_pcie_client_irq_handler+0x30/0x1a0
>> [<ffff00000813ce98>] __free_irq+0x1c8/0x2dc
>> [<ffff00000813d044>] free_irq+0x44/0x74
>> [<ffff0000081415fc>] devm_irq_release+0x24/0x2c
>> [<ffff00000877429c>] release_nodes+0x1d8/0x30c
>> [<ffff000008774838>] devres_release_all+0x3c/0x5c
>> [<ffff00000876f19c>] driver_probe_device+0x244/0x494
>> [<ffff00000876f50c>] __driver_attach+0x120/0x124
>> [<ffff00000876cb80>] bus_for_each_dev+0x6c/0xac
>> [<ffff00000876e984>] driver_attach+0x2c/0x34
>> [<ffff00000876e3a4>] bus_add_driver+0x244/0x2b0
>> [<ffff000008770264>] driver_register+0x70/0x110
>> [<ffff0000087718b4>] platform_driver_register+0x60/0x6c
>> [<ffff0000091eb108>] rockchip_pcie_driver_init+0x20/0x28
>> [<ffff000008083a2c>] do_one_initcall+0xc8/0x130
>> [<ffff0000091a0ea8>] kernel_init_freeable+0x1a0/0x238
>> [<ffff000008c461cc>] kernel_init+0x18/0x108
>> [<ffff0000080836c0>] ret_from_fork+0x10/0x50
>>
>> In order to fix this, we check the clk state before accessing the
>> pcie register in rockchip_pcie_read, but don't touch rockchip_pcie_write
>> as no case to trigger that from write routine.
>>
>> Signed-off-by: Shawn Lin <shawn.lin at rock-chips.com>
>>
>> ---
>> Hi Bjorn, Thomas and Marc,
>>
>> This fix looks more like a hack, but I don't know the legit way to
>> deal with that case. Just quick look into the drivers/pci/host, and
>> I see almost all drivers register shard irq and also disable the clk
>> in their probe's error handle path. So I guess this is NOT pcie-rockchip
>> specified even not pcie host drivers specified, but folks just luckily didn't
>> trip over it.
>>
>> Could you give some suggestion on this?
>>
>>   drivers/pci/host/pcie-rockchip.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
>> index 39aafe2..daaa868b 100644
>> --- a/drivers/pci/host/pcie-rockchip.c
>> +++ b/drivers/pci/host/pcie-rockchip.c
>> @@ -17,6 +17,7 @@
>>   
>>   #include <linux/bitrev.h>
>>   #include <linux/clk.h>
>> +#include <linux/clk-provider.h>
>>   #include <linux/delay.h>
>>   #include <linux/gpio/consumer.h>
>>   #include <linux/init.h>
>> @@ -252,6 +253,9 @@ struct rockchip_pcie {
>>   
>>   static u32 rockchip_pcie_read(struct rockchip_pcie *rockchip, u32 reg)
>>   {
>> +	if (!__clk_is_enabled(rockchip->hclk_pcie))
>> +		return 0;
>> +
>>   	return readl(rockchip->apb_base + reg);
>>   }
>>   
>>
> 
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> 
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