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SubjectRe: [PATCH v6 03/10] PCI/RCEC: Cache RCEC capabilities in pci_init_capabilities()
On Tue, Sep 22, 2020 at 02:38:52PM -0700, Sean V Kelley wrote:
> From: Sean V Kelley <sean.v.kelley@intel.com>
>
> Extend support for Root Complex Event Collectors by decoding and
> caching the RCEC Endpoint Association Extended Capabilities when
> enumerating. Use that cached information for later error source
> reporting. See PCI Express Base Specification, version 5.0-1,
> section 7.9.10.
>
> Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> Co-developed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
> Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
> ---
> drivers/pci/pci.h | 18 ++++++++++++++
> drivers/pci/pcie/Makefile | 2 +-
> drivers/pci/pcie/rcec.c | 52 +++++++++++++++++++++++++++++++++++++++
> drivers/pci/probe.c | 3 ++-
> include/linux/pci.h | 4 +++
> 5 files changed, 77 insertions(+), 2 deletions(-)
> create mode 100644 drivers/pci/pcie/rcec.c
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index fa12f7cbc1a0..83670a6425d8 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -449,6 +449,16 @@ int aer_get_device_error_info(struct pci_dev *dev, struct aer_err_info *info);
> void aer_print_error(struct pci_dev *dev, struct aer_err_info *info);
> #endif /* CONFIG_PCIEAER */
>
> +#ifdef CONFIG_PCIEPORTBUS
> +/* Cached RCEC Associated Endpoint Extended Capabilities */
> +struct rcec_ext {
> + u8 ver;
> + u8 nextbusn;
> + u8 lastbusn;
> + u32 bitmap;
> +};
> +#endif
> +
> #ifdef CONFIG_PCIE_DPC
> void pci_save_dpc_state(struct pci_dev *dev);
> void pci_restore_dpc_state(struct pci_dev *dev);
> @@ -461,6 +471,14 @@ static inline void pci_restore_dpc_state(struct pci_dev *dev) {}
> static inline void pci_dpc_init(struct pci_dev *pdev) {}
> #endif
>
> +#ifdef CONFIG_PCIEPORTBUS
> +void pci_rcec_init(struct pci_dev *dev);
> +void pci_rcec_exit(struct pci_dev *dev);
> +#else
> +static inline void pci_rcec_init(struct pci_dev *dev) {}
> +static inline void pci_rcec_exit(struct pci_dev *dev) {}
> +#endif
> +
> #ifdef CONFIG_PCI_ATS
> /* Address Translation Service */
> void pci_ats_init(struct pci_dev *dev);
> diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
> index 68da9280ff11..d9697892fa3e 100644
> --- a/drivers/pci/pcie/Makefile
> +++ b/drivers/pci/pcie/Makefile
> @@ -2,7 +2,7 @@
> #
> # Makefile for PCI Express features and port driver
>
> -pcieportdrv-y := portdrv_core.o portdrv_pci.o err.o
> +pcieportdrv-y := portdrv_core.o portdrv_pci.o err.o rcec.o
>
> obj-$(CONFIG_PCIEPORTBUS) += pcieportdrv.o
>
> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c
> new file mode 100644
> index 000000000000..519ae086ff41
> --- /dev/null
> +++ b/drivers/pci/pcie/rcec.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Root Complex Event Collector Support
> + *
> + * Authors:
> + * Sean V Kelley <sean.v.kelley@intel.com>
> + * Qiuxu Zhuo <qiuxu.zhuo@intel.com>
> + *
> + * Copyright (C) 2020 Intel Corp.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/bitops.h>
> +#include <linux/pci.h>
> +#include <linux/pci_regs.h>

Do we really need all the above? I don't see any errno or bitops
here.

> +#include "../pci.h"
> +
> +void pci_rcec_init(struct pci_dev *dev)
> +{
> + u32 rcec, hdr, busn;
> +
> + /* Only for Root Complex Event Collectors */
> + if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC)
> + return;
> +
> + dev->rcec_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_RCEC);
> + if (!dev->rcec_cap)
> + return;
> +
> + dev->rcec_ext = kzalloc(sizeof(*dev->rcec_ext), GFP_KERNEL);
> +
> + rcec = dev->rcec_cap;
> + pci_read_config_dword(dev, rcec + PCI_RCEC_RCIEP_BITMAP, &dev->rcec_ext->bitmap);
> +
> + /* Check whether RCEC BUSN register is present */
> + pci_read_config_dword(dev, rcec, &hdr);
> + dev->rcec_ext->ver = PCI_EXT_CAP_VER(hdr);
> + if (dev->rcec_ext->ver < PCI_RCEC_BUSN_REG_VER)
> + return;
> +
> + pci_read_config_dword(dev, rcec + PCI_RCEC_BUSN, &busn);
> + dev->rcec_ext->nextbusn = PCI_RCEC_BUSN_NEXT(busn);
> + dev->rcec_ext->lastbusn = PCI_RCEC_BUSN_LAST(busn);
> +}
> +
> +void pci_rcec_exit(struct pci_dev *dev)
> +{
> + kfree(dev->rcec_ext);
> + dev->rcec_ext = NULL;
> +}
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 03d37128a24f..16bc651fecb7 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2201,6 +2201,7 @@ static void pci_configure_device(struct pci_dev *dev)
> static void pci_release_capabilities(struct pci_dev *dev)
> {
> pci_aer_exit(dev);
> + pci_rcec_exit(dev);
> pci_vpd_release(dev);
> pci_iov_release(dev);
> pci_free_cap_save_buffers(dev);
> @@ -2400,7 +2401,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
> pci_ptm_init(dev); /* Precision Time Measurement */
> pci_aer_init(dev); /* Advanced Error Reporting */
> pci_dpc_init(dev); /* Downstream Port Containment */
> -
> + pci_rcec_init(dev); /* Root Complex Event Collector */
> pcie_report_downtraining(dev);
>
> if (pci_probe_reset_function(dev) == 0)
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 835530605c0d..5c5c4eb642b6 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -326,6 +326,10 @@ struct pci_dev {
> #ifdef CONFIG_PCIEAER
> u16 aer_cap; /* AER capability offset */
> struct aer_stats *aer_stats; /* AER stats for this device */
> +#endif
> +#ifdef CONFIG_PCIEPORTBUS
> + u16 rcec_cap; /* RCEC capability offset */

Looking through the whole series, I think rcec_cap is used (a) in
pci_rcec_init(), where we actually read the RCEC EA capability, and
(b) in walk_rcec() and pcie_link_rcec(), where we only use it to test
whether the device has an RCEC EA capability.

Couldn't we accomplish (b) just by testing "dev->rcec_ext"? Then we
wouldn't need to save rcec_cap at all.

> + struct rcec_ext *rcec_ext; /* RCEC cached assoc. endpoint extended capabilities */

Maybe "rcec_ea"? The important part is that this is the Endpoint
Association information. The fact that it happens to be an "extended"
capability isn't very interesting.

> #endif
> u8 pcie_cap; /* PCIe capability offset */
> u8 msi_cap; /* MSI capability offset */
> --
> 2.28.0
>

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