[PATCH v1 0/2] PCI: dwc: Remove the delay from PCIe probe path

[PATCH v1 0/2] PCI: dwc: Remove the delay from PCIe probe path

[Ajay Agarwal]

dw_pcie_host_init() waits for the link to come up regardless of
whether there has been an attempt to start the link. The 1 second
wait time is wasteful. Get rid of it if .start_link() is not
defined.

Ajay Agarwal (2):
  PCI: dwc: Add helper function to print link status
  PCI: dwc: Wait for link up only if link is started

 .../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(-)

-- 
2.43.0.429.g432eaa2c6b-goog

[PATCH v1 1/2] PCI: dwc: Add helper function to print link status

[Ajay Agarwal]

Add helper function `dw_pcie_print_link_status` to print the link
speed and width. This function can be called from various places
to print the link status when desired.

Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
---
 drivers/pci/controller/dwc/pcie-designware.c | 20 +++++++++++++-------
 drivers/pci/controller/dwc/pcie-designware.h |  1 +
 2 files changed, 14 insertions(+), 7 deletions(-)

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);
-- 
2.43.0.429.g432eaa2c6b-goog

[PATCH v1 2/2] PCI: dwc: Wait for link up only if link is started

[Ajay Agarwal]

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 one 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.

Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
---
This is actually patch v6 for [1] which I have made a part of the
patch series.

v4 [2] was applied, but then reverted [3]. 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.

[1] https://lore.kernel.org/all/20240112093006.2832105-1-ajayagarwal@google.com/
[2] https://lore.kernel.org/all/20230412093425.3659088-1-ajayagarwal@google.com/
[3] https://lore.kernel.org/all/20230706082610.26584-1-johan+linaro@kernel.org/

 drivers/pci/controller/dwc/pcie-designware-host.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 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;
 
-- 
2.43.0.429.g432eaa2c6b-goog

Re: [PATCH v1 0/2] PCI: dwc: Remove the delay from PCIe probe path

[Manivannan Sadhasivam]

On Wed, Jan 24, 2024 at 02:55:31PM +0530, Ajay Agarwal wrote:
> dw_pcie_host_init() waits for the link to come up regardless of
> whether there has been an attempt to start the link. The 1 second
> wait time is wasteful. Get rid of it if .start_link() is not
> defined.
> 

Where is the changelog? Reviewers will first take a look at the cover letter to
understand the series. And this doesn't convey full information (history).

- Mani

> Ajay Agarwal (2):
>   PCI: dwc: Add helper function to print link status
>   PCI: dwc: Wait for link up only if link is started
> 
>  .../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(-)
> 
> -- 
> 2.43.0.429.g432eaa2c6b-goog
> 

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH v1 2/2] PCI: dwc: Wait for link up only if link is started

[Manivannan Sadhasivam]

On Wed, Jan 24, 2024 at 02:55:33PM +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 one 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.
> 
> Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
> ---
> This is actually patch v6 for [1] which I have made a part of the
> patch series.
> 
> v4 [2] was applied, but then reverted [3]. 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.
> 

What happened to the previous thread [1]? You did not resolve my comment there
and posted a new series. You are not going to make progress if you skip
responding to review comments, sorry.

- Mani

[1] https://lore.kernel.org/linux-pci/20240120143434.GA5405@thinkpad/

> [1] https://lore.kernel.org/all/20240112093006.2832105-1-ajayagarwal@google.com/
> [2] https://lore.kernel.org/all/20230412093425.3659088-1-ajayagarwal@google.com/
> [3] https://lore.kernel.org/all/20230706082610.26584-1-johan+linaro@kernel.org/
> 
>  drivers/pci/controller/dwc/pcie-designware-host.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 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;
>  
> -- 
> 2.43.0.429.g432eaa2c6b-goog
> 

-- 
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