Re: [PATCH v5 02/27] sfc: add cxl support using new CXL API

[Ben Cheatham <benjamin.cheatham@amd.com>]

On 11/18/24 10:44 AM, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 
> Add CXL initialization based on new CXL API for accel drivers and make
> it dependable on kernel CXL configuration.
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> ---
>  drivers/net/ethernet/sfc/Kconfig      |  7 +++
>  drivers/net/ethernet/sfc/Makefile     |  1 +
>  drivers/net/ethernet/sfc/efx.c        | 24 +++++++-
>  drivers/net/ethernet/sfc/efx_cxl.c    | 88 +++++++++++++++++++++++++++
>  drivers/net/ethernet/sfc/efx_cxl.h    | 28 +++++++++
>  drivers/net/ethernet/sfc/net_driver.h | 10 +++
>  6 files changed, 157 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 3eb55dcfa8a6..a8bc777baa95 100644
> --- a/drivers/net/ethernet/sfc/Kconfig
> +++ b/drivers/net/ethernet/sfc/Kconfig
> @@ -65,6 +65,13 @@ 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=y && CXL_BUS=m)

If I'm reading this right, you want to make sure that CXL_BUS is not set to 'm' when SFC is built-in. If that's
the case, you can simplify this to "depends on SFC && CXL_BUS && CXL_BUS >= SFC" (or SFC <= CXL_BUS).
I'm pretty sure you could also drop the middle part as well, so it would become "depends on SFC && CXL_BUS >= SFC".
Also, this patch relies on the cxl_mem/cxl_acpi modules, right? If so, I would change the CXL_BUS above to one of
those since they already depend on CXL_BUS IIRC.

> +	default y
> +	help
> +	  This enables CXL support by the driver relying on kernel support
> +	  and hardware support.

I think it would be good here to say what kernel support is being relied on. I'm 99% sure
it's just the CXL driver, so saying it relies on the CXL driver/module(s) would be fine. I
have no clue what hardware is needed for this support, so I can't make a recommendation
there.

>  
>  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 8f446b9bd5ee..e909cafd5908 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 36b3b57e2055..5f7c910a14a5 100644
> --- a/drivers/net/ethernet/sfc/efx.c
> +++ b/drivers/net/ethernet/sfc/efx.c
> @@ -33,6 +33,9 @@
>  #include "selftest.h"
>  #include "sriov.h"
>  #include "efx_devlink.h"
> +#ifdef CONFIG_SFC_CXL
> +#include "efx_cxl.h"
> +#endif
>  
>  #include "mcdi_port_common.h"
>  #include "mcdi_pcol.h"
> @@ -903,12 +906,17 @@ 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);
> +#ifdef CONFIG_SFC_CXL
> +	efx_cxl_exit(probe_data);
> +#endif
> +
>  	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);
>  };
>  
> @@ -1113,6 +1121,17 @@ static int efx_pci_probe(struct pci_dev *pci_dev,
>  	if (rc)
>  		goto fail2;
>  
> +#ifdef CONFIG_SFC_CXL
> +	/* A successful cxl initialization implies a CXL region created to be
> +	 * used for PIO buffers. If there is no CXL support, or initialization
> +	 * fails, efx_cxl_pio_initialised wll 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);
> +
> +#endif
>  	rc = efx_pci_probe_post_io(efx);
>  	if (rc) {
>  		/* On failure, retry once immediately.
> @@ -1384,3 +1403,6 @@ MODULE_AUTHOR("Solarflare Communications and "
>  MODULE_DESCRIPTION("Solarflare network driver");
>  MODULE_LICENSE("GPL");
>  MODULE_DEVICE_TABLE(pci, efx_pci_table);
> +#ifdef CONFIG_SFC_CXL
> +MODULE_SOFTDEP("pre: cxl_core cxl_port cxl_acpi cxl-mem");
> +#endif
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> new file mode 100644
> index 000000000000..99f396028639
> --- /dev/null
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/****************************************************************************
> + *
> + * Driver for AMD network controllers and boards
> + * Copyright (C) 2024, 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.
> + */
> +
> +#include <cxl/cxl.h>
> +#include <cxl/pci.h>
> +#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;
> +	struct efx_cxl *cxl;
> +	struct resource res;
> +	u16 dvsec;
> +	int rc;
> +
> +	pci_dev = efx->pci_dev;
> +	probe_data->cxl_pio_initialised = false;
> +
> +	dvsec = pci_find_dvsec_capability(pci_dev, PCI_VENDOR_ID_CXL,
> +					  CXL_DVSEC_PCIE_DEVICE);
> +	if (!dvsec)
> +		return 0;
> +
> +	pci_dbg(pci_dev, "CXL_DVSEC_PCIE_DEVICE capability found\n");
> +
> +	cxl = kzalloc(sizeof(*cxl), GFP_KERNEL);
> +	if (!cxl)
> +		return -ENOMEM;
> +
> +	cxl->cxlds = cxl_accel_state_create(&pci_dev->dev);
> +	if (IS_ERR(cxl->cxlds)) {
> +		pci_err(pci_dev, "CXL accel device state failed");
> +		rc = -ENOMEM;
> +		goto err1;
> +	}
> +
> +	cxl_set_dvsec(cxl->cxlds, dvsec);
> +	cxl_set_serial(cxl->cxlds, pci_dev->dev.id);
> +
> +	res = DEFINE_RES_MEM(0, EFX_CTPIO_BUFFER_SIZE);
> +	if (cxl_set_resource(cxl->cxlds, res, CXL_RES_DPA)) {
> +		pci_err(pci_dev, "cxl_set_resource DPA failed\n");
> +		rc = -EINVAL;
> +		goto err2;
> +	}
> +
> +	res = DEFINE_RES_MEM_NAMED(0, EFX_CTPIO_BUFFER_SIZE, "ram");
> +	if (cxl_set_resource(cxl->cxlds, res, CXL_RES_RAM)) {
> +		pci_err(pci_dev, "cxl_set_resource RAM failed\n");
> +		rc = -EINVAL;
> +		goto err2;
> +	}
> +
> +	probe_data->cxl = cxl;
> +
> +	return 0;
> +
> +err2:
> +	kfree(cxl->cxlds);
> +err1:
> +	kfree(cxl);
> +	return rc;
> +
> +}
> +
> +void efx_cxl_exit(struct efx_probe_data *probe_data)
> +{
> +	if (probe_data->cxl) {
> +		kfree(probe_data->cxl->cxlds);
> +		kfree(probe_data->cxl);
> +	}
> +}
> +
> +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..90fa46bc94db
> --- /dev/null
> +++ b/drivers/net/ethernet/sfc/efx_cxl.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/****************************************************************************
> + * Driver for AMD network controllers and boards
> + * Copyright (C) 2024, 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
> +
> +struct efx_nic;
> +
> +struct efx_cxl {
> +	struct cxl_dev_state *cxlds;
> +	struct cxl_memdev *cxlmd;
> +	struct cxl_root_decoder *cxlrd;
> +	struct cxl_port *endpoint;
> +	struct cxl_endpoint_decoder *cxled;
> +	struct cxl_region *efx_region;
> +	void __iomem *ctpio_cxl;
> +};
> +
> +int efx_cxl_init(struct efx_probe_data *probe_data);
> +void efx_cxl_exit(struct efx_probe_data *probe_data);
> +#endif

I know nothing about the /net code so sorry if this is just a style thing, but
you can delete the #ifdef CONFIG_SFC_CXL in efx.c (and elsewhere) if you add stubs
for when CONFIG_SFC_CXL=n. So the above would look like:

#if IS_ENABLED(CONFIG_SFC_CXL) // or #ifdef CONFIG_SFC_CXL
int efx_cxl_init(struct efx_probe_data *probe_data);
void efx_cxl_exit(struct efx_probe_data *probe_data);
#else
static inline int efx_cxl_init(struct efx_probe_data *probe_data) { return 0; }
static inline void efx_cxl_exit(struct efx_probe_data *probe_data) {}
#endif

and then you can just #include efx_cxl.h unconditionally.

> diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
> index b85c51cbe7f9..efc6d90380b9 100644
> --- a/drivers/net/ethernet/sfc/net_driver.h
> +++ b/drivers/net/ethernet/sfc/net_driver.h
> @@ -1160,14 +1160,24 @@ 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)