Re: [PATCH v5] PCI: dwc: Wait for link up only if link is started

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Jan 12, 2024 at 03:00:06PM +0530, Ajay Agarwal wrote:
> In dw_pcie_host_init() regardless of whether the link has been
> started or not, the code waits for the link to come up. Even in
> cases where start_link() is not defined the code ends up spinning
> in a loop for 1 second. Since in some systems dw_pcie_host_init()
> gets called during probe, this one second loop for each pcie
> interface instance ends up extending the boot time.
> 

Which platform you are working on? Is that upstreamed? You should mention the
specific platform where you are observing the issue.

Right now, intel-gw and designware-plat are the only drivers not defining that
callback. First one definitely needs a fixup and I do not know how the latter
works.

- Mani

> Wait for the link up in only if the start_link() is defined.
> 
> Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
> ---
> v4 was applied, but then reverted. The reason being v4 added a
> regression on some products which expect the link to not come up as a
> part of the probe. Since v4 returned error from dw_pcie_wait_for_link
> check, the probe function of these products started to fail.
> 
> Changelog since v4:
>  - Do not return error from dw_pcie_wait_for_link check
> 
>  .../pci/controller/dwc/pcie-designware-host.c | 12 +++++++----
>  drivers/pci/controller/dwc/pcie-designware.c  | 20 ++++++++++++-------
>  drivers/pci/controller/dwc/pcie-designware.h  |  1 +
>  3 files changed, 22 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 7991f0e179b2..e53132663d1d 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -487,14 +487,18 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
>  	if (ret)
>  		goto err_remove_edma;
>  
> -	if (!dw_pcie_link_up(pci)) {
> +	if (dw_pcie_link_up(pci)) {
> +		dw_pcie_print_link_status(pci);
> +	} else {
>  		ret = dw_pcie_start_link(pci);
>  		if (ret)
>  			goto err_remove_edma;
> -	}
>  
> -	/* Ignore errors, the link may come up later */
> -	dw_pcie_wait_for_link(pci);
> +		if (pci->ops && pci->ops->start_link) {
> +			/* 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.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 250cf7f40b85..c067d2e960cf 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -645,9 +645,20 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index)
>  	dw_pcie_writel_atu(pci, dir, index, PCIE_ATU_REGION_CTRL2, 0);
>  }
>  
> -int dw_pcie_wait_for_link(struct dw_pcie *pci)
> +void dw_pcie_print_link_status(struct dw_pcie *pci)
>  {
>  	u32 offset, val;
> +
> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
> +
> +	dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
> +		 FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
> +		 FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
> +}
> +
> +int dw_pcie_wait_for_link(struct dw_pcie *pci)
> +{
>  	int retries;
>  
>  	/* Check if the link is up or not */
> @@ -663,12 +674,7 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
>  		return -ETIMEDOUT;
>  	}
>  
> -	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> -	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
> -
> -	dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
> -		 FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
> -		 FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
> +	dw_pcie_print_link_status(pci);
>  
>  	return 0;
>  }
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 55ff76e3d384..164214a7219a 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -447,6 +447,7 @@ void dw_pcie_setup(struct dw_pcie *pci);
>  void dw_pcie_iatu_detect(struct dw_pcie *pci);
>  int dw_pcie_edma_detect(struct dw_pcie *pci);
>  void dw_pcie_edma_remove(struct dw_pcie *pci);
> +void dw_pcie_print_link_status(struct dw_pcie *pci);
>  
>  int dw_pcie_suspend_noirq(struct dw_pcie *pci);
>  int dw_pcie_resume_noirq(struct dw_pcie *pci);
> -- 
> 2.43.0.381.gb435a96ce8-goog
> 

-- 
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