[PATCH v26 1/8] sfc: add cxl support

[<alejandro.lucero-palau@amd.com>]

From: Alejandro Lucero <alucerop@amd.com>

Add CXL initialization based on new CXL API for accel drivers and make
it dependent on kernel CXL configuration.

Signed-off-by: Alejandro Lucero <alucerop@amd.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/net/ethernet/sfc/Kconfig      |  9 +++++
 drivers/net/ethernet/sfc/Makefile     |  1 +
 drivers/net/ethernet/sfc/efx.c        | 14 +++++++-
 drivers/net/ethernet/sfc/efx_cxl.c    | 52 +++++++++++++++++++++++++++
 drivers/net/ethernet/sfc/efx_cxl.h    | 29 +++++++++++++++
 drivers/net/ethernet/sfc/net_driver.h | 10 ++++++
 6 files changed, 114 insertions(+), 1 deletion(-)
 create mode 100644 drivers/net/ethernet/sfc/efx_cxl.c
 create mode 100644 drivers/net/ethernet/sfc/efx_cxl.h

diff --git a/drivers/net/ethernet/sfc/Kconfig b/drivers/net/ethernet/sfc/Kconfig
index c4c43434f314..979f2801e2a8 100644
--- a/drivers/net/ethernet/sfc/Kconfig
+++ b/drivers/net/ethernet/sfc/Kconfig
@@ -66,6 +66,15 @@ config SFC_MCDI_LOGGING
 	  Driver-Interface) commands and responses, allowing debugging of
 	  driver/firmware interaction.  The tracing is actually enabled by
 	  a sysfs file 'mcdi_logging' under the PCI device.
+config SFC_CXL
+	bool "Solarflare SFC9100-family CXL support"
+	depends on SFC && CXL_BUS >= SFC
+	default SFC
+	help
+	  This enables SFC CXL support if the kernel is configuring CXL for
+	  using CTPIO with CXL.mem. The SFC device with CXL support and
+	  with a CXL-aware firmware can be used for minimizing latencies
+	  when sending through CTPIO.
 
 source "drivers/net/ethernet/sfc/falcon/Kconfig"
 source "drivers/net/ethernet/sfc/siena/Kconfig"
diff --git a/drivers/net/ethernet/sfc/Makefile b/drivers/net/ethernet/sfc/Makefile
index d99039ec468d..bb0f1891cde6 100644
--- a/drivers/net/ethernet/sfc/Makefile
+++ b/drivers/net/ethernet/sfc/Makefile
@@ -13,6 +13,7 @@ sfc-$(CONFIG_SFC_SRIOV)	+= sriov.o ef10_sriov.o ef100_sriov.o ef100_rep.o \
                            mae.o tc.o tc_bindings.o tc_counters.o \
                            tc_encap_actions.o tc_conntrack.o
 
+sfc-$(CONFIG_SFC_CXL)	+= efx_cxl.o
 obj-$(CONFIG_SFC)	+= sfc.o
 
 obj-$(CONFIG_SFC_FALCON) += falcon/
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 8f136a11d396..90ccbe310386 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -34,6 +34,7 @@
 #include "selftest.h"
 #include "sriov.h"
 #include "efx_devlink.h"
+#include "efx_cxl.h"
 
 #include "mcdi_port_common.h"
 #include "mcdi_pcol.h"
@@ -981,12 +982,14 @@ static void efx_pci_remove(struct pci_dev *pci_dev)
 	efx_pci_remove_main(efx);
 
 	efx_fini_io(efx);
+
+	probe_data = container_of(efx, struct efx_probe_data, efx);
+
 	pci_dbg(efx->pci_dev, "shutdown successful\n");
 
 	efx_fini_devlink_and_unlock(efx);
 	efx_fini_struct(efx);
 	free_netdev(efx->net_dev);
-	probe_data = container_of(efx, struct efx_probe_data, efx);
 	kfree(probe_data);
 };
 
@@ -1190,6 +1193,15 @@ static int efx_pci_probe(struct pci_dev *pci_dev,
 	if (rc)
 		goto fail2;
 
+	/* A successful cxl initialization implies a CXL region created to be
+	 * used for PIO buffers. If there is no CXL support, or initialization
+	 * fails, cxl_pio_initialised will be false and legacy PIO buffers
+	 * defined at specific PCI BAR regions will be used.
+	 */
+	rc = efx_cxl_init(probe_data);
+	if (rc)
+		pci_err(pci_dev, "CXL initialization failed with error %d\n", rc);
+
 	rc = efx_pci_probe_post_io(efx);
 	if (rc) {
 		/* On failure, retry once immediately.
diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
new file mode 100644
index 000000000000..b7e8d85a43d3
--- /dev/null
+++ b/drivers/net/ethernet/sfc/efx_cxl.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/****************************************************************************
+ *
+ * Driver for AMD network controllers and boards
+ * Copyright (C) 2025, Advanced Micro Devices, Inc.
+ */
+
+#include <linux/pci.h>
+
+#include "net_driver.h"
+#include "efx_cxl.h"
+
+#define EFX_CTPIO_BUFFER_SIZE	SZ_256M
+
+int efx_cxl_init(struct efx_probe_data *probe_data)
+{
+	struct efx_nic *efx = &probe_data->efx;
+	struct pci_dev *pci_dev = efx->pci_dev;
+	struct efx_cxl *cxl;
+	u16 dvsec;
+
+	probe_data->cxl_pio_initialised = false;
+
+	/* Is the device configured with and using CXL? */
+	if (!pcie_is_cxl(pci_dev))
+		return 0;
+
+	dvsec = pci_find_dvsec_capability(pci_dev, PCI_VENDOR_ID_CXL,
+					  PCI_DVSEC_CXL_DEVICE);
+	if (!dvsec) {
+		pci_info(pci_dev, "CXL_DVSEC_PCIE_DEVICE capability not found\n");
+		return 0;
+	}
+
+	pci_dbg(pci_dev, "CXL_DVSEC_PCIE_DEVICE capability found\n");
+
+	/* Create a cxl_dev_state embedded in the cxl struct using cxl core api
+	 * specifying no mbox available.
+	 */
+	cxl = devm_cxl_dev_state_create(&pci_dev->dev, CXL_DEVTYPE_DEVMEM,
+					pci_get_dsn(pci_dev), dvsec,
+					struct efx_cxl, cxlds, false);
+
+	if (!cxl)
+		return -ENOMEM;
+
+	probe_data->cxl = cxl;
+
+	return 0;
+}
+
+MODULE_IMPORT_NS("CXL");
diff --git a/drivers/net/ethernet/sfc/efx_cxl.h b/drivers/net/ethernet/sfc/efx_cxl.h
new file mode 100644
index 000000000000..04e46278464d
--- /dev/null
+++ b/drivers/net/ethernet/sfc/efx_cxl.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/****************************************************************************
+ * Driver for AMD network controllers and boards
+ * Copyright (C) 2025, Advanced Micro Devices, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation, incorporated herein by reference.
+ */
+
+#ifndef EFX_CXL_H
+#define EFX_CXL_H
+
+#ifdef CONFIG_SFC_CXL
+
+#include <cxl/cxl.h>
+
+struct efx_probe_data;
+
+struct efx_cxl {
+	struct cxl_dev_state cxlds;
+	struct cxl_memdev *cxlmd;
+};
+
+int efx_cxl_init(struct efx_probe_data *probe_data);
+#else
+static inline int efx_cxl_init(struct efx_probe_data *probe_data) { return 0; }
+#endif
+#endif
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index b98c259f672d..3964b2c56609 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -1197,14 +1197,24 @@ struct efx_nic {
 	atomic_t n_rx_noskb_drops;
 };
 
+#ifdef CONFIG_SFC_CXL
+struct efx_cxl;
+#endif
+
 /**
  * struct efx_probe_data - State after hardware probe
  * @pci_dev: The PCI device
  * @efx: Efx NIC details
+ * @cxl: details of related cxl objects
+ * @cxl_pio_initialised: cxl initialization outcome.
  */
 struct efx_probe_data {
 	struct pci_dev *pci_dev;
 	struct efx_nic efx;
+#ifdef CONFIG_SFC_CXL
+	struct efx_cxl *cxl;
+	bool cxl_pio_initialised;
+#endif
 };
 
 static inline struct efx_nic *efx_netdev_priv(struct net_device *dev)
-- 
2.34.1