linux-kernel - Re: [PATCH 09/11] PCI: epf-test: Handle Link Down event

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Message-ID: <Zf2tg9I6ZBxp7asU@ryzen>
Date: Fri, 22 Mar 2024 17:10:43 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
	linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mhi@...ts.linux.dev,
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH 09/11] PCI: epf-test: Handle Link Down event

On Thu, Mar 14, 2024 at 08:53:48PM +0530, Manivannan Sadhasivam wrote:
> As per the PCIe base spec r5.0, section 5.2, Link Down event can happen
> under any of the following circumstances:
> 
> 1. Fundamental/Hot reset
> 2. Link disable transmission by upstream component
> 3. Moving from L2/L3 to L0
> 
> When the event happens, the EPC driver capable of detecting it may pass the
> notification to the EPF driver through link_down() callback in 'struct
> pci_epc_bus_event_ops'.
> 
> While the PCIe spec has not defined the actual behavior of the endpoint
> when the Link Down event happens, we may assume that atleast the ongoing

Nit:
s/atleast/at least/

Reviewed-by: Niklas Cassel <cassel@...nel.org>

> transactions need to be stopped as the link won't be active. So let's
> cancel the command handler work in the callback implementation
> pci_epf_test_link_down(). The work will be started again in
> pci_epf_test_link_up() once the link comes back again.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 84cd47ebac22..97245228c9eb 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -823,6 +823,15 @@ static int pci_epf_test_link_up(struct pci_epf *epf)
>  	return 0;
>  }
>  
> +static int pci_epf_test_link_down(struct pci_epf *epf)
> +{
> +	struct pci_epf_test *epf_test = epf_get_drvdata(epf);
> +
> +	cancel_delayed_work(&epf_test->cmd_handler);
> +
> +	return 0;
> +}
> +
>  static const struct pci_epc_event_ops pci_epf_test_epc_event_ops = {
>  	.init = pci_epf_test_epc_init,
>  	.deinit = pci_epf_test_epc_deinit,
> @@ -830,6 +839,7 @@ static const struct pci_epc_event_ops pci_epf_test_epc_event_ops = {
>  
>  static const struct pci_epc_bus_event_ops pci_epf_test_bus_event_ops = {
>  	.link_up = pci_epf_test_link_up,
> +	.link_down = pci_epf_test_link_down,
>  };
>  
>  static int pci_epf_test_alloc_space(struct pci_epf *epf)
> 
> -- 
> 2.25.1
>