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Date: Mon, 1 Nov 2021 18:28:18 +0100
From: Borislav Petkov <bp@...en8.de>
To: Naveen Krishna Chatradhi <nchatrad@....com>
Cc: linux-edac@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org, mingo@...hat.com, mchehab@...nel.org,
yazen.ghannam@....com, Muralidhara M K <muralimk@....com>
Subject: Re: [PATCH v6 1/5] x86/amd_nb: Add support for northbridges on
Aldebaran
On Thu, Oct 28, 2021 at 06:31:02PM +0530, Naveen Krishna Chatradhi wrote:
> +/* GPU Data Fabric ID Device 24 Function 1 */
> +#define PCI_DEVICE_ID_AMD_ALDEBARAN_DF_F1 0x14d1
> +
> +/* DF18xF1 registers on Aldebaran GPU */
> +#define REG_LOCAL_NODE_TYPE_MAP 0x144
> +#define REG_RMT_NODE_TYPE_MAP 0x148
Move those defines up, along with the rest of them. While at it, you can
align them all vertically.
> +
> +/*
> + * Newer AMD CPUs and GPUs whose data fabrics can be connected via custom xGMI
"Newer" is a commit message type of adjective and doesn't belong in
permanent comments because when years pass, they won't be "newer"
anymore. IOW, you can simply drop it here.
> + * links, comes with registers to gather local and remote node type map info.
"come"
> + *
> + * "Local Node Type" refers to nodes with the same type as that from which the
> + * register is read, and "Remote Node Type" refers to nodes with a different type.
This sure sounds weird.
With my simplistic thinking I'd assume "local" is the CPU and "remote"
is the GPU...
> + * This function, reads the registers from GPU DF function 1.
> + * Hence, local nodes are GPU and remote nodes are CPUs.
> + */
> +static int amd_get_node_map(void)
> +{
> + struct amd_node_map *nodemap;
> + struct pci_dev *pdev;
> + u32 tmp;
> +
> + pdev = pci_get_device(PCI_VENDOR_ID_AMD,
> + PCI_DEVICE_ID_AMD_ALDEBARAN_DF_F1, NULL);
> + if (!pdev) {
> + pr_debug("DF Func1 PCI device not found on this node.\n");
> + return -ENODEV;
> + }
> +
> + nodemap = kmalloc(sizeof(*nodemap), GFP_KERNEL);
You allocate a whopping 4 bytes? Just do
struct amd_node_map nodemap;
in the nb info descriptor.
I still need to see whether those node maps and functions you're adding
and exporting even make sense but that will happen later.
> + if (!nodemap)
> + return -ENOMEM;
> +
> + pci_read_config_dword(pdev, REG_LOCAL_NODE_TYPE_MAP, &tmp);
Check retval.
> + nodemap->gpu_node_start_id = tmp & 0xFFF;
> +
> + pci_read_config_dword(pdev, REG_RMT_NODE_TYPE_MAP, &tmp);
Ditto.
> + nodemap->cpu_node_count = tmp >> 16 & 0xFFF;
> +
> + amd_northbridges.nodemap = nodemap;
> + return 0;
> +}
> +
> static struct pci_dev *next_northbridge(struct pci_dev *dev,
> const struct pci_device_id *ids)
> {
> @@ -230,6 +297,27 @@ int amd_df_indirect_read(u16 node, u8 func, u16 reg, u8 instance_id, u32 *lo)
> }
> EXPORT_SYMBOL_GPL(amd_df_indirect_read);
>
> +struct pci_dev *get_root_devs(struct pci_dev *root,
static
> + const struct pci_device_id *root_ids,
> + u16 roots_per_misc)
> +{
> + u16 j;
> +
> + /*
> + * If there are more PCI root devices than data fabric/
> + * system management network interfaces, then the (N)
> + * PCI roots per DF/SMN interface are functionally the
> + * same (for DF/SMN access) and N-1 are redundant. N-1
> + * PCI roots should be skipped per DF/SMN interface so
> + * the following DF/SMN interfaces get mapped to
> + * correct PCI roots.
> + */
> + for (j = 0; j < roots_per_misc; j++)
> + root = next_northbridge(root, root_ids);
> +
> + return root;
> +}
> +
> int amd_cache_northbridges(void)
> {
> const struct pci_device_id *misc_ids = amd_nb_misc_ids;
> @@ -237,10 +325,10 @@ int amd_cache_northbridges(void)
> const struct pci_device_id *root_ids = amd_root_ids;
> struct pci_dev *root, *misc, *link;
> struct amd_northbridge *nb;
> - u16 roots_per_misc = 0;
> - u16 misc_count = 0;
> - u16 root_count = 0;
> - u16 i, j;
> + u16 roots_per_misc = 0, gpu_roots_per_misc = 0;
> + u16 misc_count = 0, gpu_misc_count = 0;
> + u16 root_count = 0, gpu_root_count = 0;
> + u16 i;
>
> if (amd_northbridges.num)
> return 0;
> @@ -252,15 +340,23 @@ int amd_cache_northbridges(void)
> }
>
> misc = NULL;
> - while ((misc = next_northbridge(misc, misc_ids)) != NULL)
> - misc_count++;
> + while ((misc = next_northbridge(misc, misc_ids)) != NULL) {
Just remove that redundant "!= NULL" at the end, while at it.
> + if (misc->device == PCI_DEVICE_ID_AMD_ALDEBARAN_DF_F3)
> + gpu_misc_count++;
> + else
> + misc_count++;
> + }
>
> if (!misc_count)
> return -ENODEV;
>
> root = NULL;
> - while ((root = next_northbridge(root, root_ids)) != NULL)
> - root_count++;
> + while ((root = next_northbridge(root, root_ids)) != NULL) {
> + if (root->device == PCI_DEVICE_ID_AMD_ALDEBARAN_ROOT)
> + gpu_root_count++;
> + else
> + root_count++;
> + }
>
> if (root_count) {
> roots_per_misc = root_count / misc_count;
> @@ -275,33 +371,37 @@ int amd_cache_northbridges(void)
> }
> }
>
> - nb = kcalloc(misc_count, sizeof(struct amd_northbridge), GFP_KERNEL);
> + /*
> + * The number of miscs, roots and roots_per_misc might vary on different
> + * nodes of a heterogeneous system.
> + * Calculate roots_per_misc accordingly in order to skip the redundant
> + * roots and map the DF/SMN interfaces to correct PCI roots.
> + */
Reflow that comment so that it is a block.
> + if (gpu_root_count && gpu_misc_count) {
> + int ret = amd_get_node_map();
> +
^ Superfluous newline.
> + if (ret)
> + return ret;
> +
> + gpu_roots_per_misc = gpu_root_count / gpu_misc_count;
> + }
> +
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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