Re: [PATCH v2 1/2] PCI: endpoint: pci-epf-test: Add support for capabilities

Frank Li
2024-11-21T19:39:09Z

On Thu, Nov 21, 2024 at 04:23:20PM +0100, Niklas Cassel wrote:
> The test BAR is on the EP side is allocated using pci_epf_alloc_space(),
> which allocates the backing memory using dma_alloc_coherent(), which will
> return zeroed memory regardless of __GFP_ZERO was set or not.
>
> This means that running a new version of pci-endpoint-test.c (host side)
> with an old version of pci-epf-test.c (EP side) will not see any
> capabilities being set (as intended), so this is backwards compatible.
>
> Additionally, the EP side always allocates at least 128 bytes for the test
> BAR (excluding the MSI-X table), this means that adding another register at
> offset 0x30 is still within the 128 available bytes.
>
> For now, we only add the CAP_UNALIGNED_ACCESS capability.
>
> Set CAP_UNALIGNED_ACCESS if the EPC driver can handle any address (because
> it implements the .align_addr callback).
>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

Reviewed-by: Frank Li <Frank.Li@nxp.com>
> ---
> drivers/pci/endpoint/functions/pci-epf-test.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index ef6677f34116..7351289ecddd 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -44,6 +44,8 @@
>
> #define TIMER_RESOLUTION 1
>
> +#define CAP_UNALIGNED_ACCESS BIT(0)
> +
> static struct workqueue_struct *kpcitest_workqueue;
>
> struct pci_epf_test {
> @@ -74,6 +76,7 @@ struct pci_epf_test_reg {
> u32 irq_type;
> u32 irq_number;
> u32 flags;
> + u32 caps;
> } __packed;
>
> static struct pci_epf_header test_header = {
> @@ -739,6 +742,20 @@ static void pci_epf_test_clear_bar(struct pci_epf *epf)
> }
> }
>
> +static void pci_epf_test_set_capabilities(struct pci_epf *epf)
> +{
> + struct pci_epf_test *epf_test = epf_get_drvdata(epf);
> + enum pci_barno test_reg_bar = epf_test->test_reg_bar;
> + struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
> + struct pci_epc *epc = epf->epc;
> + u32 caps = 0;
> +
> + if (epc->ops->align_addr)
> + caps |= CAP_UNALIGNED_ACCESS;
> +
> + reg->caps = cpu_to_le32(caps);
> +}
> +
> static int pci_epf_test_epc_init(struct pci_epf *epf)
> {
> struct pci_epf_test *epf_test = epf_get_drvdata(epf);
> @@ -763,6 +780,8 @@ static int pci_epf_test_epc_init(struct pci_epf *epf)
> }
> }
>
> + pci_epf_test_set_capabilities(epf);
> +
> ret = pci_epf_test_set_bar(epf);
> if (ret)
> return ret;
> --
> 2.47.0
>