linux-kernel - Re: [PATCH] PCI: rockchip: Avoid accessing PCIe registers with clocks gated【请注意，邮件由linux-rockchip-bounces+shawn.lin=rock-chips.com@...ts.infradead.org代发】

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Message-ID: <c3f49fe5-edbe-2889-bd59-92891adc807b@rock-chips.com>
Date:   Tue, 8 Jun 2021 14:48:45 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     shawn.lin@...k-chips.com, Peter Robinson <pbrobinson@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: rockchip: Avoid accessing PCIe registers with clocks gated【请注意，邮件由linux-rockchip-bounces+shawn.lin=rock-chips.com@...ts.infradead.org代发】

On 2021/6/8 5:33, Javier Martinez Canillas wrote:
> IRQ handlers that are registered for shared interrupts can be called at
> any time after have been registered using the request_irq() function.
> 
> It's up to drivers to ensure that's always safe for these to be called.
> 
> Both the "pcie-sys" and "pcie-client" interrupts are shared, but since
> their handlers are registered very early in the probe function, an error
> later can lead to these handlers being executed before all the required
> have been properly setup.
> 
> For example, the rockchip_pcie_read() function used by these IRQ handlers
> expects that some PCIe clocks will already be enabled, otherwise trying
> to access the PCIe registers causes the read to hang and never return.
> 
> The CONFIG_DEBUG_SHIRQ option tests if drivers are able to cope with their
> shared interrupt handlers being called, by generating a spurious interrupt
> just before a shared interrupt handler is unregistered.
> 
> But this means that if the option is enabled, any error in the probe path
> of this driver could lead to one of the IRQ handlers to be executed.
> 
> In a rockpro64 board, the following sequence of events happens:
> 
>    1) "pcie-sys" IRQ is requested and its handler registered.
>    2) "pcie-client" IRQ is requested and its handler registered.
>    3) probe later fails due readl_poll_timeout() returning a timeout.
>    4) the "pcie-sys" IRQ is unregistered.
>    5) CONFIG_DEBUG_SHIRQ triggers a spurious interrupt.
>    6) "pcie-client" IRQ handler is called for this spurious interrupt.
>    7) IRQ handler tries to read PCIE_CLIENT_INT_STATUS with clocks gated.
>    8) the machine hangs because rockchip_pcie_read() call never returns.
> 
> To avoid cases like this, the handlers don't have to be registered until
> very late in the probe function, once all the resources have been setup.
> 
> So let's just move all the IRQ init before the pci_host_probe() call, that
> will prevent issues like this and seems to be the correct thing to do too.
> 

Acked-by: Shawn Lin <shawn.lin@...k-chips.com>

Thanks.

> Reported-by: Peter Robinson <pbrobinson@...il.com>
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> ---
> 
>   drivers/pci/controller/pcie-rockchip-host.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
> index f1d08a1b159..78d04ac29cd 100644
> --- a/drivers/pci/controller/pcie-rockchip-host.c
> +++ b/drivers/pci/controller/pcie-rockchip-host.c
> @@ -592,10 +592,6 @@ static int rockchip_pcie_parse_host_dt(struct rockchip_pcie *rockchip)
>   	if (err)
>   		return err;
>   
> -	err = rockchip_pcie_setup_irq(rockchip);
> -	if (err)
> -		return err;
> -
>   	rockchip->vpcie12v = devm_regulator_get_optional(dev, "vpcie12v");
>   	if (IS_ERR(rockchip->vpcie12v)) {
>   		if (PTR_ERR(rockchip->vpcie12v) != -ENODEV)
> @@ -973,8 +969,6 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
>   	if (err)
>   		goto err_vpcie;
>   
> -	rockchip_pcie_enable_interrupts(rockchip);
> -
>   	err = rockchip_pcie_init_irq_domain(rockchip);
>   	if (err < 0)
>   		goto err_deinit_port;
> @@ -992,6 +986,12 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
>   	bridge->sysdata = rockchip;
>   	bridge->ops = &rockchip_pcie_ops;
>   
> +	err = rockchip_pcie_setup_irq(rockchip);
> +	if (err)
> +		goto err_remove_irq_domain;
> +
> +	rockchip_pcie_enable_interrupts(rockchip);
> +
>   	err = pci_host_probe(bridge);
>   	if (err < 0)
>   		goto err_remove_irq_domain;
>