Re: [RFC PATCH 2/9] cxl/acpi: add OSC support

Jonathan Cameron
2020-11-16T17:59:43Z

On Tue, 10 Nov 2020 21:43:49 -0800
Ben Widawsky <ben.widawsky@intel.com> wrote:

> From: Vishal Verma <vishal.l.verma@intel.com>
>
> Add support to advertise OS capabilities, and request OS control for CXL
> features using the ACPI _OSC mechanism. Advertise support for all
> possible CXL features, and attempt to request control too for all
> possible features.
>
> Based on a patch by Sean Kelley.
>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>

I guess unsurprisingly a lot of this is cut and paste from PCIe
so can we share some of the code?

Thanks,

Jonathan

>
> ---
>
> This uses a non-standard UUID for CXL and is meant as a change proposal
> to the CXL specification. The definition for _OSC intermixes PCIe and
> CXL Dwords, which makes a clean separation of CXL capabilities
> difficult, if not impossible. This is therefore subject to change.
>
> ---
> drivers/cxl/acpi.c | 210 ++++++++++++++++++++++++++++++++++++++++++++-
> drivers/cxl/acpi.h | 18 ++++
> 2 files changed, 226 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 26e4f73838a7..c3e2f7f6ea02 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -12,6 +12,16 @@
> #include <linux/pci.h>
> #include "acpi.h"
>
> +/*
> + * TODO: These are global for now to save the OSC state.
> + * This works if OSC can be expected to be uniform for every ACPI0016 object.
> + * If that is not the case, revisit this. These need to be saved because
> + * relinquishing control of a previously granted capability is disallowed.
> + */
> +static u32 cxl_osc_support_set;
> +static u32 cxl_osc_control_set;
> +static DEFINE_MUTEX(acpi_desc_lock);
> +
> static void acpi_cxl_desc_init(struct acpi_cxl_desc *acpi_desc, struct device *dev)
> {
> dev_set_drvdata(dev, acpi_desc);
> @@ -74,6 +84,199 @@ static struct acpi_driver acpi_cxl_driver = {
> },
> };
>
> +struct pci_osc_bit_struct {
> + u32 bit;
> + char *desc;
> +};
> +
> +static struct pci_osc_bit_struct cxl_osc_support_bit[] = {
> + { CXL_OSC_PORT_REG_ACCESS_SUPPORT, "CXLPortRegAccess" },
> + { CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT, "CXLPortDevRegAccess" },
> + { CXL_OSC_PER_SUPPORT, "CXLProtocolErrorReporting" },
> + { CXL_OSC_NATIVE_HP_SUPPORT, "CXLNativeHotPlug" },
> +};
> +
> +static struct pci_osc_bit_struct cxl_osc_control_bit[] = {
> + { CXL_OSC_MEM_ERROR_CONTROL, "CXLMemErrorReporting" },
> +};
> +
> +/*
> + * CXL 2.0 spec UUID - unusable as it PCI and CXL OSC are mixed
> + * static u8 cxl_osc_uuid_str[] = "68F2D50B-C469-4d8A-BD3D-941A103FD3FC";
> + */
> +/* New, proposed UUID for CXL-only OSC */
> +static u8 cxl_osc_uuid_str[] = "A4D1629D-FF52-4888-BE96-E5CADE548DB1";
> +
> +static void decode_osc_bits(struct device *dev, char *msg, u32 word,
> + struct pci_osc_bit_struct *table, int size)
> +{
> + char buf[80];
> + int i, len = 0;
> + struct pci_osc_bit_struct *entry;
> +
> + buf[0] = '\0';
> + for (i = 0, entry = table; i < size; i++, entry++)
> + if (word & entry->bit)
> + len += scnprintf(buf + len, sizeof(buf) - len, "%s%s",
> + len ? " " : "", entry->desc);
> +
> + dev_info(dev, "_OSC: %s [%s]\n", msg, buf);

Can we look at sharing code with PCI?

> +}
> +
> +static void decode_cxl_osc_support(struct device *dev, char *msg, u32 word)
> +{
> + decode_osc_bits(dev, msg, word, cxl_osc_support_bit,
> + ARRAY_SIZE(cxl_osc_support_bit));
> +}
> +
> +static void decode_cxl_osc_control(struct device *dev, char *msg, u32 word)
> +{
> + decode_osc_bits(dev, msg, word, cxl_osc_control_bit,
> + ARRAY_SIZE(cxl_osc_control_bit));
> +}
> +
> +static acpi_status acpi_cap_run_osc(acpi_handle handle,
> + const u32 *capbuf, u8 *uuid_str, u32 *retval)
> +{
> + struct acpi_osc_context context = {
> + .uuid_str = uuid_str,
> + .rev = 1,
> + .cap.length = 20,
> + .cap.pointer = (void *)capbuf,
> + };
> + acpi_status status;
> +
> + status = acpi_run_osc(handle, &context);
> + if (ACPI_SUCCESS(status)) {
> + *retval = *((u32 *)(context.ret.pointer + 8));
> + kfree(context.ret.pointer);
> + }
> + return status;
> +}
> +
> +static acpi_status cxl_query_osc(acpi_handle handle, u32 support, u32 *control)
> +{
> + acpi_status status;
> + u32 result, capbuf[5];
> +
> + support &= CXL_OSC_SUPPORT_VALID_MASK;
> + support |= cxl_osc_support_set;
> +
> + capbuf[OSC_QUERY_DWORD] = OSC_QUERY_ENABLE;
> + capbuf[CXL_OSC_SUPPORT_DWORD] = support;
> + if (control) {
> + *control &= CXL_OSC_CONTROL_VALID_MASK;
> + capbuf[CXL_OSC_CONTROL_DWORD] = *control | cxl_osc_control_set;
> + } else {
> + /* Run _OSC query only with existing controls. */
> + capbuf[CXL_OSC_CONTROL_DWORD] = cxl_osc_control_set;
> + }
> +
> + status = acpi_cap_run_osc(handle, capbuf, cxl_osc_uuid_str, &result);
> + if (ACPI_SUCCESS(status)) {
> + cxl_osc_support_set = support;
> + if (control)
> + *control = result;
> + }
> + return status;
> +}
> +
> +static acpi_status cxl_osc_advertise_support(acpi_handle handle, u32 flags)
> +{
> + acpi_status status;
> +
> + mutex_lock(&acpi_desc_lock);
> + status = cxl_query_osc(handle, flags, NULL);
> + mutex_unlock(&acpi_desc_lock);
> + return status;
> +}
> +
> +/**
> + * cxl_osc_request_control - Request control of CXL root _OSC features.
> + * @adev: ACPI device for the PCI root bridge (or PCIe Root Complex).
> + * @mask: Mask of _OSC bits to request control of, place to store control mask.
> + * @req: Mask of _OSC bits the control of is essential to the caller.
> + **/
> +static acpi_status cxl_osc_request_control(struct acpi_device *adev, u32 *mask, u32 req)
> +{
> + acpi_handle handle = adev->handle;
> + struct device *dev = &adev->dev;
> + acpi_status status = AE_OK;
> + u32 ctrl, capbuf[5];
> +
> + if (!mask)
> + return AE_BAD_PARAMETER;
> +
> + ctrl = *mask & CXL_OSC_MEM_ERROR_CONTROL;
> + if ((ctrl & req) != req)
> + return AE_TYPE;
> +
> + mutex_lock(&acpi_desc_lock);
> +
> + *mask = ctrl | cxl_osc_control_set;
> + /* No need to evaluate _OSC if the control was already granted. */
> + if ((cxl_osc_control_set & ctrl) == ctrl)
> + goto out;
> +
> + /* Need to check the available controls bits before requesting them. */
> + while (*mask) {
> + status = cxl_query_osc(handle, cxl_osc_support_set, mask);
> + if (ACPI_FAILURE(status))
> + goto out;
> + if (ctrl == *mask)
> + break;
> + decode_cxl_osc_control(dev, "platform does not support", ctrl & ~(*mask));
> + ctrl = *mask;
> + }
> +
> + if ((ctrl & req) != req) {
> + decode_cxl_osc_control(dev, "not requesting control; platform does not support",
> + req & ~(ctrl));
> + status = AE_SUPPORT;
> + goto out;
> + }
> +
> + capbuf[OSC_QUERY_DWORD] = 0;
> + capbuf[CXL_OSC_SUPPORT_DWORD] = cxl_osc_support_set;
> + capbuf[CXL_OSC_CONTROL_DWORD] = ctrl;
> + status = acpi_cap_run_osc(handle, capbuf, cxl_osc_uuid_str, mask);
> + if (ACPI_SUCCESS(status))
> + cxl_osc_control_set = *mask;
> +out:
> + mutex_unlock(&acpi_desc_lock);
> + return status;
> +}
> +
> +static int cxl_negotiate_osc(struct acpi_device *adev)
> +{
> + u32 cxl_support, cxl_control, requested;
> + acpi_handle handle = adev->handle;
> + struct device *dev = &adev->dev;
> + acpi_status status;
> +
> + /* Declare support for everything */
> + cxl_support = CXL_OSC_SUPPORT_VALID_MASK;
> + decode_cxl_osc_support(dev, "OS supports", cxl_support);
> + status = cxl_osc_advertise_support(handle, cxl_support);
> + if (ACPI_FAILURE(status)) {
> + dev_info(dev, "CXL_OSC failed (%s)\n", acpi_format_exception(status));
> + return -ENXIO;
> + }
> +
> + /* Request control for everything */
> + cxl_control = CXL_OSC_CONTROL_VALID_MASK;
> + requested = cxl_control;
> + status = cxl_osc_request_control(adev, &cxl_control, CXL_OSC_MEM_ERROR_CONTROL);
> + if (ACPI_SUCCESS(status)) {
> + decode_cxl_osc_control(dev, "OS now controls", cxl_control);
> + } else {
> + decode_cxl_osc_control(dev, "OS requested", requested);
> + decode_cxl_osc_control(dev, "platform willing to grant", cxl_control);
> + dev_info(dev, "_OSC failed (%s)\n", acpi_format_exception(status));
> + }
> + return 0;
> +}
> +
> /*
> * If/when CXL support is defined by other platform firmware the kernel
> * will need a mechanism to select between the platform specific version
> @@ -84,6 +287,7 @@ int cxl_bus_prepared(struct pci_dev *pdev)
> struct acpi_device *adev;
> struct pci_dev *root_port;
> struct device *root;
> + int rc;
>
> root_port = pcie_find_root_port(pdev);
> if (!root_port)
> @@ -97,9 +301,11 @@ int cxl_bus_prepared(struct pci_dev *pdev)
> if (!adev)
> return -ENXIO;
>
> - /* TODO: OSC enabling */
> + rc = cxl_negotiate_osc(adev);
> + if (rc)
> + dev_err(&pdev->dev, "Failed to negotiate OSC\n");
>
> - return 0;
> + return rc;
> }
> EXPORT_SYMBOL_GPL(cxl_bus_prepared);
>
> diff --git a/drivers/cxl/acpi.h b/drivers/cxl/acpi.h
> index 011505475cc6..bf8d078e1b2a 100644
> --- a/drivers/cxl/acpi.h
> +++ b/drivers/cxl/acpi.h
> @@ -10,6 +10,24 @@ struct acpi_cxl_desc {
> struct device *dev;
> };
>
> +/* Indexes into _OSC Capabilities Buffer */
> +#define CXL_OSC_SUPPORT_DWORD 1 /* DWORD 2 */
> +#define CXL_OSC_CONTROL_DWORD 2 /* DWORD 3 */
> +
> +/* CXL Host Bridge _OSC: Capabilities DWORD 2: Support Field */
> +#define CXL_OSC_PORT_REG_ACCESS_SUPPORT 0x00000001
> +#define CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT 0x00000002
> +#define CXL_OSC_PER_SUPPORT 0x00000004
> +#define CXL_OSC_NATIVE_HP_SUPPORT 0x00000008
> +#define CXL_OSC_SUPPORT_VALID_MASK (CXL_OSC_PORT_REG_ACCESS_SUPPORT | \
> + CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT | \
> + CXL_OSC_PER_SUPPORT | \
> + CXL_OSC_NATIVE_HP_SUPPORT)
> +
> +/* CXL Host Bridge _OSC: Capabilities DWORD 3: Control Field */
> +#define CXL_OSC_MEM_ERROR_CONTROL 0x00000001
> +#define CXL_OSC_CONTROL_VALID_MASK (CXL_OSC_MEM_ERROR_CONTROL)
> +
> int cxl_bus_prepared(struct pci_dev *pci_dev);
>
> #endif /* __CXL_ACPI_H__ */