Re: [PATCH 1/4] PCI: add resizeable BAR infrastructure v4

From: Alex Deucher
Date: Tue Apr 25 2017 - 11:01:16 EST

On Tue, Apr 25, 2017 at 9:19 AM, Christian KÃnig
<deathsimple@xxxxxxxxxxx> wrote:
> From: Christian KÃnig <christian.koenig@xxxxxxx>
>
> Just the defines and helper functions to read the possible sizes of a BAR and
> update it's size.
>
> See https://pcisig.com/sites/default/files/specification_documents/ECN_Resizable-BAR_24Apr2008.pdf
> and PCIe r3.1, sec 7.22.
>
> This is useful for hardware with large local storage (mostly GFX) which only
> expose 256MB BARs initially to be compatible with 32bit systems.
>
> v2: provide read helper as well
> v3: improve function names, use unsigned values, add better comments.
> v4: move definition, improve commit message, s/bar/BAR/
>
> Signed-off-by: Christian KÃnig <christian.koenig@xxxxxxx>


Patches 1, 2:
Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx>

> ---
> drivers/pci/pci.c | 115 ++++++++++++++++++++++++++++++++++++++++++
> drivers/pci/pci.h | 4 ++
> include/uapi/linux/pci_regs.h | 11 +++-
> 3 files changed, 128 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index ba34907..c2d9f78 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2944,6 +2944,121 @@ bool pci_acs_path_enabled(struct pci_dev *start,
> }
>
> /**
> + * pci_rbar_get_possible_sizes - get possible sizes for BAR
> + * @dev: PCI device
> + * @bar: BAR to query
> + *
> + * Get the possible sizes of a resizeable BAR as bitmask defined in the spec
> + * (bit 0=1MB, bit 19=512GB). Returns 0 if BAR isn't resizeable.
> + */
> +u32 pci_rbar_get_possible_sizes(struct pci_dev *pdev, int bar)
> +{
> + unsigned pos, nbars;
> + u32 ctrl, cap;
> + unsigned i;
> +
> + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
> + if (!pos)
> + return 0;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> + nbars = (ctrl & PCI_REBAR_CTRL_NBAR_MASK) >> PCI_REBAR_CTRL_NBAR_SHIFT;
> +
> + for (i = 0; i < nbars; ++i, pos += 8) {
> + int bar_idx;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> + bar_idx = (ctrl & PCI_REBAR_CTRL_BAR_IDX_MASK) >>
> + PCI_REBAR_CTRL_BAR_IDX_SHIFT;
> + if (bar_idx != bar)
> + continue;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CAP, &cap);
> + return (cap & PCI_REBAR_CTRL_SIZES_MASK) >>
> + PCI_REBAR_CTRL_SIZES_SHIFT;
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * pci_rbar_get_current_size - get the current size of a BAR
> + * @dev: PCI device
> + * @bar: BAR to set size to
> + *
> + * Read the size of a BAR from the resizeable BAR config.
> + * Returns size if found or negativ error code.
> + */
> +int pci_rbar_get_current_size(struct pci_dev *pdev, int bar)
> +{
> + unsigned pos, nbars;
> + u32 ctrl;
> + unsigned i;
> +
> + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
> + if (!pos)
> + return -ENOTSUPP;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> + nbars = (ctrl & PCI_REBAR_CTRL_NBAR_MASK) >> PCI_REBAR_CTRL_NBAR_SHIFT;
> +
> + for (i = 0; i < nbars; ++i, pos += 8) {
> + int bar_idx;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> + bar_idx = (ctrl & PCI_REBAR_CTRL_BAR_IDX_MASK) >>
> + PCI_REBAR_CTRL_BAR_IDX_SHIFT;
> + if (bar_idx != bar)
> + continue;
> +
> + return (ctrl & PCI_REBAR_CTRL_BAR_SIZE_MASK) >>
> + PCI_REBAR_CTRL_BAR_SIZE_SHIFT;
> + }
> +
> + return -ENOENT;
> +}
> +
> +/**
> + * pci_rbar_set_size - set a new size for a BAR
> + * @dev: PCI device
> + * @bar: BAR to set size to
> + * @size: new size as defined in the spec (log2(size in bytes) - 20)
> + *
> + * Set the new size of a BAR as defined in the spec (0=1MB, 19=512GB).
> + * Returns true if resizing was successful, false otherwise.
> + */
> +int pci_rbar_set_size(struct pci_dev *pdev, int bar, int size)
> +{
> + unsigned pos, nbars;
> + u32 ctrl;
> + unsigned i;
> +
> + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
> + if (!pos)
> + return -ENOTSUPP;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> + nbars = (ctrl & PCI_REBAR_CTRL_NBAR_MASK) >> PCI_REBAR_CTRL_NBAR_SHIFT;
> +
> + for (i = 0; i < nbars; ++i, pos += 8) {
> + int bar_idx;
> +
> + pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
> + bar_idx = (ctrl & PCI_REBAR_CTRL_BAR_IDX_MASK) >>
> + PCI_REBAR_CTRL_BAR_IDX_SHIFT;
> + if (bar_idx != bar)
> + continue;
> +
> + ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE_MASK;
> + ctrl |= size << PCI_REBAR_CTRL_BAR_SIZE_SHIFT;
> + pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
> + return 0;
> + }
> +
> + return -ENOENT;
> +}
> +
> +/**
> * pci_swizzle_interrupt_pin - swizzle INTx for device behind bridge
> * @dev: the PCI device
> * @pin: the INTx pin (1=INTA, 2=INTB, 3=INTC, 4=INTD)
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 4518562..1d27c22 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -356,4 +356,8 @@ static inline int pci_dev_specific_reset(struct pci_dev *dev, int probe)
> }
> #endif
>
> +u32 pci_rbar_get_possible_sizes(struct pci_dev *pdev, int bar);
> +int pci_rbar_get_current_size(struct pci_dev *pdev, int bar);
> +int pci_rbar_set_size(struct pci_dev *pdev, int bar, int size);
> +
> #endif /* DRIVERS_PCI_H */
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index e5a2e68..a75429e 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -932,9 +932,16 @@
> #define PCI_SATA_SIZEOF_LONG 16
>
> /* Resizable BARs */
> +#define PCI_REBAR_CAP 4 /* capability register */
> +#define PCI_REBAR_CTRL_SIZES_MASK (0xFFFFF << 4) /* mask for sizes */
> +#define PCI_REBAR_CTRL_SIZES_SHIFT 4 /* shift for sizes */
> #define PCI_REBAR_CTRL 8 /* control register */
> -#define PCI_REBAR_CTRL_NBAR_MASK (7 << 5) /* mask for # bars */
> -#define PCI_REBAR_CTRL_NBAR_SHIFT 5 /* shift for # bars */
> +#define PCI_REBAR_CTRL_BAR_IDX_MASK (7 << 0) /* mask for BAR index */
> +#define PCI_REBAR_CTRL_BAR_IDX_SHIFT 0 /* shift for BAR index */
> +#define PCI_REBAR_CTRL_NBAR_MASK (7 << 5) /* mask for # BARs */
> +#define PCI_REBAR_CTRL_NBAR_SHIFT 5 /* shift for # BARs */
> +#define PCI_REBAR_CTRL_BAR_SIZE_MASK (0x1F << 8) /* mask for BAR size */
> +#define PCI_REBAR_CTRL_BAR_SIZE_SHIFT 8 /* shift for BAR size */
>
> /* Dynamic Power Allocation */
> #define PCI_DPA_CAP 4 /* capability register */
> --
> 2.7.4
>
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