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SubjectRe: [PATCH 10/15] cxl/acpi: Extract the RCH's RCRB base address from CEDT
On Wed, 31 Aug 2022 10:15:58 +0200
Robert Richter <rrichter@amd.com> wrote:

> The downstream and upstream port Root Complex Register Blocks (RCRBs)
> are needed to control the ports and CXL devices connected to it. It
> also includes the location of the RCH/RCD downstream and upstream port
> component registers in MEMBAR0. Extract the RCRB from the host's CEDT
> entry.
>
> Signed-off-by: Robert Richter <rrichter@amd.com>
Hi Robert,

One trivial comment inline.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
> drivers/cxl/acpi.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index b3146b7ae922..439df9df2741 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -365,11 +365,48 @@ struct pci_host_bridge *cxl_find_next_rch(struct pci_host_bridge *host)
> return NULL;
> }
>
> +static int __cxl_get_rcrb(union acpi_subtable_headers *header, void *arg,
> + const unsigned long end)
> +{
> + struct cxl_chbs_context *ctx = arg;
> + struct acpi_cedt_chbs *chbs;
> +
> + if (ctx->chbcr)
> + return 0;
> +
> + chbs = (struct acpi_cedt_chbs *)header;
> +
> + if (ctx->uid != chbs->uid)
> + return 0;
> +
> + if (chbs->cxl_version != ACPI_CEDT_CHBS_VERSION_CXL11)
> + return 0;
> +
> + if (chbs->length != SZ_8K)
> + return 0;
> +
> + ctx->chbcr = chbs->base;
> +
> + return 0;
> +}
> +
> +static resource_size_t cxl_get_rcrb(u32 uid)
> +{
> + struct cxl_chbs_context ctx = {
> + .uid = uid,
> + };
> +
> + acpi_table_parse_cedt(ACPI_CEDT_TYPE_CHBS, __cxl_get_rcrb, &ctx);
> +
> + return ctx.chbcr;
> +}
> +
> static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> {
> struct pci_host_bridge *host = NULL;
> struct acpi_device *adev;
> unsigned long long uid = ~0;
> + resource_size_t rcrb;

Some of these could be made local to the while loop to reduce their scope.
>
> while ((host = cxl_find_next_rch(host)) != NULL) {
> adev = ACPI_COMPANION(&host->dev);
> @@ -382,6 +419,12 @@ static int __init cxl_restricted_host_probe(struct platform_device *pdev)
> if (uid > U32_MAX)
> continue;
>
> + rcrb = cxl_get_rcrb(uid);
> + if (!rcrb)
> + continue;
> +
> + dev_dbg(&host->dev, "RCRB found: 0x%08llx\n", (u64)rcrb);
> +
> dev_info(&host->dev, "host supports CXL\n");
> }
>

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