linux-kernel - Re: [PATCH v4 1/3] PCI: dwc: Skip waiting for link up if vendor drivers can detect Link up event

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Message-ID: <20241115134524.xbjgrutbpp7ehjsn@thinkpad>
Date: Fri, 15 Nov 2024 19:15:24 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Jingoo Han <jingoohan1@...il.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Konrad Dybcio <konradybcio@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	quic_vbadigan@...cinc.com, quic_mrana@...cinc.com,
	andersson@...nel.org
Subject: Re: [PATCH v4 1/3] PCI: dwc: Skip waiting for link up if vendor
 drivers can detect Link up event

On Fri, Nov 15, 2024 at 04:00:21PM +0530, Krishna chaitanya chundru wrote:
> If the vendor drivers can detect the Link up event using mechanisms
> such as Link up IRQ and can the driver can enumerate downstream devices

"if the driver can..."

> instead of waiting here, then waiting for Link up during probe is not
> needed here, which optimizes the boot time.
> 
> So skip waiting for link to be up if the driver supports 'linkup_irq'.
> 

s/linkup_irq/use_linkup_irq

> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>

With above,

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 10 ++++++++--
>  drivers/pci/controller/dwc/pcie-designware.h      |  1 +
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 3e41865c7290..c8208a6c03d1 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -530,8 +530,14 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
>  			goto err_remove_edma;
>  	}
>  
> -	/* Ignore errors, the link may come up later */
> -	dw_pcie_wait_for_link(pci);
> +	/*
> +	 * Note: The link up delay is skipped only when a link up IRQ is present.
> +	 * This flag should not be used to bypass the link up delay for arbitrary
> +	 * reasons.
> +	 */
> +	if (!pp->use_linkup_irq)
> +		/* Ignore errors, the link may come up later */
> +		dw_pcie_wait_for_link(pci);
>  
>  	bridge->sysdata = pp;
>  
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 347ab74ac35a..1d0ec47e1986 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -379,6 +379,7 @@ struct dw_pcie_rp {
>  	bool			use_atu_msg;
>  	int			msg_atu_index;
>  	struct resource		*msg_res;
> +	bool			use_linkup_irq;
>  };
>  
>  struct dw_pcie_ep_ops {
> 
> -- 
> 2.34.1
> 

-- 
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