On Tue, Apr 16, 2019 at 04:21:44PM +0530, Vidya Sagar wrote:
> Since the upstream MSI memory writes are generated by downstream devices,
> it is logically correct to have MSI target memory coming from the DMA pool
> reserved for PCIe than from the general memory pool reserved for CPU
> access. This avoids PCIe DMA addresses coinciding with MSI target address
> thereby raising unwanted MSI interrupts. This patch also enforces to limit
> the MSI target address to 32-bits to make it work for PCIe endponits that
> support only 32-bit MSI target address and those endpoints that support
> 64-bit MSI target address anyway work with 32-bit MSI target address.
>
> Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> Reviewed-by: Thierry Reding <treding@xxxxxxxxxx>
> Acked-by: Thierry Reding <treding@xxxxxxxxxx>
> ---
> v3:
> * replaced dma_alloc_coherent(), dma_free_coherent() APIs with
> dma_alloc_attrs(), dma_free_attrs() APIs along with
> DMA_ATTR_NO_KERNEL_MAPPING flag to indicate that there is no
> need to create kernel mapping for it.
>
> v2:
> * changed 'phys' type to 'dma_addr_t' from 'u64'
> * added a comment on why DMA mask is set to 32-bit
> * replaced 'dma' with 'DMA'
>
> drivers/pci/controller/pci-tegra.c | 37 ++++++++++++++++++++++--------
> 1 file changed, 28 insertions(+), 9 deletions(-)
Applied to pci/tegra for v5.2.
Thanks,
Lorenzo
> diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
> index f4f53d092e00..464ba2538d52 100644
> --- a/drivers/pci/controller/pci-tegra.c
> +++ b/drivers/pci/controller/pci-tegra.c
> @@ -231,9 +231,9 @@ struct tegra_msi {
> struct msi_controller chip;
> DECLARE_BITMAP(used, INT_PCI_MSI_NR);
> struct irq_domain *domain;
> - unsigned long pages;
> struct mutex lock;
> - u64 phys;
> + void *virt;
> + dma_addr_t phys;
> int irq;
> };
>
> @@ -1536,7 +1536,7 @@ static int tegra_pcie_msi_setup(struct tegra_pcie *pcie)
> err = platform_get_irq_byname(pdev, "msi");
> if (err < 0) {
> dev_err(dev, "failed to get IRQ: %d\n", err);
> - goto err;
> + goto free_irq_domain;
> }
>
> msi->irq = err;
> @@ -1545,17 +1545,35 @@ static int tegra_pcie_msi_setup(struct tegra_pcie *pcie)
> tegra_msi_irq_chip.name, pcie);
> if (err < 0) {
> dev_err(dev, "failed to request IRQ: %d\n", err);
> - goto err;
> + goto free_irq_domain;
> + }
> +
> + /* Though the PCIe controller can address >32-bit address space, to
> + * facilitate endpoints that support only 32-bit MSI target address,
> + * the mask is set to 32-bit to make sure that MSI target address is
> + * always a 32-bit address
> + */
> + err = dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
> + if (err < 0) {
> + dev_err(dev, "failed to set DMA coherent mask: %d\n", err);
> + goto free_irq;
> + }
> +
> + msi->virt = dma_alloc_attrs(dev, PAGE_SIZE, &msi->phys, GFP_KERNEL,
> + DMA_ATTR_NO_KERNEL_MAPPING);
> + if (!msi->virt) {
> + dev_err(dev, "failed to allocate DMA memory for MSI\n");
> + err = -ENOMEM;
> + goto free_irq;
> }
>
> - /* setup AFI/FPCI range */
> - msi->pages = __get_free_pages(GFP_KERNEL, 0);
> - msi->phys = virt_to_phys((void *)msi->pages);
> host->msi = &msi->chip;
>
> return 0;
>
> -err:
> +free_irq:
> + free_irq(msi->irq, pcie);
> +free_irq_domain:
> irq_domain_remove(msi->domain);
> return err;
> }
> @@ -1592,7 +1610,8 @@ static void tegra_pcie_msi_teardown(struct tegra_pcie *pcie)
> struct tegra_msi *msi = &pcie->msi;
> unsigned int i, irq;
>
> - free_pages(msi->pages, 0);
> + dma_free_attrs(pcie->dev, PAGE_SIZE, msi->virt, msi->phys,
> + DMA_ATTR_NO_KERNEL_MAPPING);
>
> if (msi->irq > 0)
> free_irq(msi->irq, pcie);
> --
> 2.17.1
>
