Re: [PATCH 3/5] PCI: sg2042: Add Sophgo SG2042 PCIe driver

[ALOK TIWARI <alok.a.tiwari@oracle.com>]

On 8/28/2025 7:47 AM, Chen Wang wrote:
> From: Chen Wang <unicorn_wang@outlook.com>
> 
> Add support for PCIe controller in SG2042 SoC. The controller
> uses the Cadence PCIe core programmed by pcie-cadence*.c. The
> PCIe controller will work in host mode only.
> 
> Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
> ---
>   drivers/pci/controller/cadence/Kconfig       |  12 ++
>   drivers/pci/controller/cadence/Makefile      |   1 +
>   drivers/pci/controller/cadence/pcie-sg2042.c | 134 +++++++++++++++++++
>   3 files changed, 147 insertions(+)
>   create mode 100644 drivers/pci/controller/cadence/pcie-sg2042.c
> 
> diff --git a/drivers/pci/controller/cadence/Kconfig b/drivers/pci/controller/cadence/Kconfig
> index 666e16b6367f..b1f1941d5208 100644
> --- a/drivers/pci/controller/cadence/Kconfig
> +++ b/drivers/pci/controller/cadence/Kconfig
> @@ -42,6 +42,17 @@ config PCIE_CADENCE_PLAT_EP
>   	  endpoint mode. This PCIe controller may be embedded into many
>   	  different vendors SoCs.
>   
> +config PCIE_SG2042
> +	bool "Sophgo SG2042 PCIe controller (host mode)"
> +	depends on ARCH_SOPHGO || COMPILE_TEST
> +	depends on OF
> +	depends on PCI_MSI
> +	select PCIE_CADENCE_HOST
> +	help
> +	  Say Y here if you want to support the Sophgo SG2042 PCIe platform
> +	  controller in host mode. Sophgo SG2042 PCIe controller uses Cadence
> +	  PCIe core.
> +
>   config PCI_J721E
>   	tristate
>   	select PCIE_CADENCE_HOST if PCI_J721E_HOST != n
> @@ -67,4 +78,5 @@ config PCI_J721E_EP
>   	  Say Y here if you want to support the TI J721E PCIe platform
>   	  controller in endpoint mode. TI J721E PCIe controller uses Cadence PCIe
>   	  core.
> +
>   endmenu
> diff --git a/drivers/pci/controller/cadence/Makefile b/drivers/pci/controller/cadence/Makefile
> index 9bac5fb2f13d..4df4456d9539 100644
> --- a/drivers/pci/controller/cadence/Makefile
> +++ b/drivers/pci/controller/cadence/Makefile
> @@ -4,3 +4,4 @@ obj-$(CONFIG_PCIE_CADENCE_HOST) += pcie-cadence-host.o
>   obj-$(CONFIG_PCIE_CADENCE_EP) += pcie-cadence-ep.o
>   obj-$(CONFIG_PCIE_CADENCE_PLAT) += pcie-cadence-plat.o
>   obj-$(CONFIG_PCI_J721E) += pci-j721e.o
> +obj-$(CONFIG_PCIE_SG2042) += pcie-sg2042.o
> diff --git a/drivers/pci/controller/cadence/pcie-sg2042.c b/drivers/pci/controller/cadence/pcie-sg2042.c
> new file mode 100644
> index 000000000000..fe434dc2967e
> --- /dev/null
> +++ b/drivers/pci/controller/cadence/pcie-sg2042.c
> @@ -0,0 +1,134 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * pcie-sg2042 - PCIe controller driver for Sophgo SG2042 SoC
> + *
> + * Copyright (C) 2025 Sophgo Technology Inc.
> + * Copyright (C) 2025 Chen Wang <unicorn_wang@outlook.com>
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/of.h>
> +#include <linux/pci.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +
> +#include "pcie-cadence.h"
> +
> +/*
> + * SG2042 only support 4-byte aligned access, so for the rootbus (i.e. to read

support -> supports

> + * the Root Port itself, read32 is required. For non-rootbus (i.e. to read
> + * the PCIe peripheral registers, supports 1/2/4 byte aligned access, so
> + * directly using read should be fine.
> + *
> + * The same is true for write.
[clip]
> +static int sg2042_pcie_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct pci_host_bridge *bridge;
> +	struct cdns_pcie *pcie;
> +	struct cdns_pcie_rc *rc;
> +	int ret;
> +
> +	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
> +	if (!pcie)
> +		return -ENOMEM;
> +
> +	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
> +	if (!bridge) {
> +		dev_err(dev, "Failed to alloc host bridge!\n");
> +		return -ENOMEM;
> +	}
> +
> +	bridge->ops = &sg2042_pcie_host_ops;
> +
> +	rc = pci_host_bridge_priv(bridge);
> +	pcie = &rc->pcie;
First, pcie is allocated and then reassigned to &rc->pcie,
which makes the initial allocation effectively leaked and unnecessary.

> +	pcie->dev = dev;
> +
> +	platform_set_drvdata(pdev, pcie);
> +
> +	pm_runtime_enable(dev);
> +
> +	ret = pm_runtime_get_sync(dev);
> +	if (ret < 0) {
> +		dev_err(dev, "pm_runtime_get_sync failed\n");
> +		goto err_get_sync;
> +	}
> +
> +	ret = cdns_pcie_init_phy(dev, pcie);
> +	if (ret) {
> +		dev_err(dev, "Failed to init phy!\n");
> +		goto err_get_sync;
> +	}
> +
> +	ret = cdns_pcie_host_setup(rc);
> +	if (ret < 0) {
> +		dev_err(dev, "Failed to setup host!\n");
> +		goto err_host_setup;
> +	}
> +
> +	return 0;
> +
> +err_host_setup:
> +	cdns_pcie_disable_phy(pcie);
> +
> +err_get_sync:
> +	pm_runtime_put(dev);
> +	pm_runtime_disable(dev);
> +
> +	return ret;
> +}


Thanks,
Alok