Re: [PATCH v3 18/26] PCI: endpoint: Add support to allocate aligned buffers to be mapped in BARs

Lorenzo Pieralisi
2019-04-11T15:32:47Z

On Mon, Mar 25, 2019 at 03:09:39PM +0530, Kishon Vijay Abraham I wrote:
> Modify pci_epf_alloc_space API to take alignment size as argument in
> order to argument in order to allocate aligned buffers to be mapped to
> BARs.
>
> Add 'align' parameter to epc_features which can be used by platform
> drivers to specifiy the BAR allocation alignment requirements and use
> this while invoking pci_epf_alloc_space.
>
> This is mainly required for Synopsys Designware PCIe core which masks
> the lower bits based on the BAR size (See "I/O and MEM Match Modes"
> section in DesignWare Cores PCI Express Controller Databook version
> 4.90a).

Hi Kishon,

isn't this a generic PCI BAR requirement rather than a Designware
specific one ?

The patch is fine I just would like to understand the statement above.

Thanks,
Lorenzo

> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
> drivers/pci/endpoint/functions/pci-epf-test.c | 5 +++--
> drivers/pci/endpoint/pci-epf-core.c | 10 ++++++++--
> include/linux/pci-epc.h | 2 ++
> include/linux/pci-epf.h | 3 ++-
> 4 files changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index d0b91da49bf4..c0786ca74312 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -438,7 +438,7 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
> epc_features = epf_test->epc_features;
>
> base = pci_epf_alloc_space(epf, sizeof(struct pci_epf_test_reg),
> - test_reg_bar);
> + test_reg_bar, epc_features->align);
> if (!base) {
> dev_err(dev, "Failed to allocated register space\n");
> return -ENOMEM;
> @@ -453,7 +453,8 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
> if (!!(epc_features->reserved_bar & (1 << bar)))
> continue;
>
> - base = pci_epf_alloc_space(epf, bar_size[bar], bar);
> + base = pci_epf_alloc_space(epf, bar_size[bar], bar,
> + epc_features->align);
> if (!base)
> dev_err(dev, "Failed to allocate space for BAR%d\n",
> bar);
> diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> index 8bfdcd291196..fb1306de8f40 100644
> --- a/drivers/pci/endpoint/pci-epf-core.c
> +++ b/drivers/pci/endpoint/pci-epf-core.c
> @@ -109,10 +109,12 @@ EXPORT_SYMBOL_GPL(pci_epf_free_space);
> * pci_epf_alloc_space() - allocate memory for the PCI EPF register space
> * @size: the size of the memory that has to be allocated
> * @bar: the BAR number corresponding to the allocated register space
> + * @align: alignment size for the allocation region
> *
> * Invoke to allocate memory for the PCI EPF register space.
> */
> -void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar)
> +void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> + size_t align)
> {
> void *space;
> struct device *dev = epf->epc->dev.parent;
> @@ -120,7 +122,11 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar)
>
> if (size < 128)
> size = 128;
> - size = roundup_pow_of_two(size);
> +
> + if (align)
> + size = ALIGN(size, align);
> + else
> + size = roundup_pow_of_two(size);
>
> space = dma_alloc_coherent(dev, size, &phys_addr, GFP_KERNEL);
> if (!space) {
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index c3ffa3917f88..f641badc2c61 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -109,6 +109,7 @@ struct pci_epc {
> * @reserved_bar: bitmap to indicate reserved BAR unavailable to function driver
> * @bar_fixed_64bit: bitmap to indicate fixed 64bit BARs
> * @bar_fixed_size: Array specifying the size supported by each BAR
> + * @align: alignment size required for BAR buffer allocation
> */
> struct pci_epc_features {
> unsigned int linkup_notifier : 1;
> @@ -117,6 +118,7 @@ struct pci_epc_features {
> u8 reserved_bar;
> u8 bar_fixed_64bit;
> u64 bar_fixed_size[BAR_5 + 1];
> + size_t align;
> };
>
> #define to_pci_epc(device) container_of((device), struct pci_epc, dev)
> diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> index ec02f58758c8..2d6f07556682 100644
> --- a/include/linux/pci-epf.h
> +++ b/include/linux/pci-epf.h
> @@ -149,7 +149,8 @@ void pci_epf_destroy(struct pci_epf *epf);
> int __pci_epf_register_driver(struct pci_epf_driver *driver,
> struct module *owner);
> void pci_epf_unregister_driver(struct pci_epf_driver *driver);
> -void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar);
> +void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
> + size_t align);
> void pci_epf_free_space(struct pci_epf *epf, void *addr, enum pci_barno bar);
> int pci_epf_bind(struct pci_epf *epf);
> void pci_epf_unbind(struct pci_epf *epf);
> --
> 2.17.1
>