Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu to PCIe path

[Bjorn Helgaas]

Capitalize "ICC" and "CPU" to make the subject easier to read.
"Missing" might be superfluous in the subject?  It would be nice to
have the ICC expansion once in the commit log as a hook for newbies
like me :)

On Fri, Jan 12, 2024 at 07:52:02PM +0530, Krishna chaitanya chundru wrote:
> CPU-PCIe path consits for registers PCIe BAR space, config space.
> As there is less access on this path compared to pcie to mem path
> add minimum vote i.e GEN1x1 bandwidth always.

"GEN1x1" is unnecessarily ambiguous, and the spec recommends avoiding
it (PCIe r6.0, sec 1.2).  Use the actual bandwidth numbers instead.

"PCIe" to match above.  Also below in comments and messages.

> In suspend remove the cpu vote after register space access is done.

"CPU" to match above.

> Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support")
> cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 31 +++++++++++++++++++++++++++++--
>  1 file changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 11c80555d975..035953f0b6d8 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -240,6 +240,7 @@ struct qcom_pcie {
>  	struct phy *phy;
>  	struct gpio_desc *reset;
>  	struct icc_path *icc_mem;
> +	struct icc_path *icc_cpu;
>  	const struct qcom_pcie_cfg *cfg;
>  	struct dentry *debugfs;
>  	bool suspended;
> @@ -1372,6 +1373,9 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>  	if (IS_ERR(pcie->icc_mem))
>  		return PTR_ERR(pcie->icc_mem);
>  
> +	pcie->icc_cpu = devm_of_icc_get(pci->dev, "cpu-pcie");
> +	if (IS_ERR(pcie->icc_cpu))
> +		return PTR_ERR(pcie->icc_cpu);
>  	/*
>  	 * Some Qualcomm platforms require interconnect bandwidth constraints
>  	 * to be set before enabling interconnect clocks.
> @@ -1381,7 +1385,18 @@ static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>  	 */
>  	ret = icc_set_bw(pcie->icc_mem, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
>  	if (ret) {
> -		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> +		dev_err(pci->dev, "failed to set interconnect bandwidth for pcie-mem: %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * The config space, BAR space and registers goes through cpu-pcie path.
> +	 * Set peak bandwidth to single-lane Gen1 for this path all the time.

Numbers instead of "Gen1".

> +	 */
> +	ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
> +	if (ret) {
> +		dev_err(pci->dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n",
>  			ret);
>  		return ret;
>  	}
> @@ -1573,7 +1588,7 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  	 */
>  	ret = icc_set_bw(pcie->icc_mem, 0, kBps_to_icc(1));
>  	if (ret) {
> -		dev_err(dev, "Failed to set interconnect bandwidth: %d\n", ret);
> +		dev_err(dev, "Failed to set interconnect bandwidth for pcie-mem: %d\n", ret);
>  		return ret;
>  	}
>  
> @@ -1597,6 +1612,12 @@ static int qcom_pcie_suspend_noirq(struct device *dev)
>  		pcie->suspended = true;
>  	}
>  
> +	/* Remove cpu path vote after all the register access is done */
> +	ret = icc_set_bw(pcie->icc_cpu, 0, 0);
> +	if (ret) {
> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
> +		return ret;
> +	}
>  	return 0;
>  }
>  
> @@ -1605,6 +1626,12 @@ static int qcom_pcie_resume_noirq(struct device *dev)
>  	struct qcom_pcie *pcie = dev_get_drvdata(dev);
>  	int ret;
>  
> +	ret = icc_set_bw(pcie->icc_cpu, 0, QCOM_PCIE_LINK_SPEED_TO_BW(1));
> +	if (ret) {
> +		dev_err(dev, "failed to set interconnect bandwidth for cpu-pcie: %d\n", ret);
> +		return ret;
> +	}
> +
>  	if (pcie->suspended) {
>  		ret = qcom_pcie_host_init(&pcie->pci->pp);
>  		if (ret)
> 
> -- 
> 2.42.0
>