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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: o0gHrZQhwbl47cuTZl94vESHCk9PqBl7NTgatPI1Xyv7osOy219M6Nx/eMKPg6eQvQ460Phu2BLeBhvKWn1da1wQM5GZeZkIEIPtDjuZpUP7T/0baIq3VxkmaVGNiQotrskbf7N7iU7mZsT5U8x7jGHwIRT01qfgIjCEnjGYofsI/NR1EP6IR6VUGcyefvQXEcBjESIKDVH8tLKAIlw0oSxKGYbic8BNbtZ1GcN2QJpkKIfvf7Z3IwhPTzNJU7l02y1mgJBDrTeL0Yz3tOhioBkjyB/g2CK29dwGux7DsNZ3nbHnm5BkyoUIGAZu/eUfudxYigKC2Fb6lMrejn0ljG1pT6iw+zrfxU5RxfVc8nLCNmMAS/fwua2ctex1j7u+NnFV9p9jRwVy6G8kTV5o9Hn70DWBpX+LEaF6cJZKoxaDVeN0RbKCPFEYt0TB00gX X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jul 2026 13:21:07.9964 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 031e03fd-4998-4be5-2bcb-08deebe1eb4c X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AM4PEPF00027A64.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MRWPR08MB11708 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260727_062117_043483_D2408002 X-CRM114-Status: GOOD ( 33.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 27, 2026 at 02:48:47PM +0200, Lorenzo Pieralisi wrote: > On Fri, Jul 24, 2026 at 11:18:32AM +0100, Sudeep Holla wrote: > > On Thu, Jul 23, 2026 at 05:54:54PM +0200, Andre Przywara wrote: > > > The Arm MPAM-Fb specification [1] describes a protocol to access MSC > > > registers through a firmware interface. This requires a shared memory > > > region to hold the message, and a mailbox to trigger the access. > > > For ACPI this is wrapped as a PCC channel, described using existing > > > ACPI abstractions. > > > > > > Add code to parse those PCC table descriptions associated with an MSC, > > > and store the parsed information in the MSC struct. > > > There can be multiple PCC channels, and each channel can serve multiple > > > MSCs, so we need to keep track of the channel usage, using a list and > > > a refcount. > > > This will be used by the MPAM-Fb access wrapper code. > > > > > > [1] https://developer.arm.com/documentation/den0144/latest > > > > > > Signed-off-by: Andre Przywara > > > --- > > > drivers/acpi/arm64/mpam.c | 6 +- > > > drivers/resctrl/mpam_devices.c | 127 ++++++++++++++++++++++++++++++++- > > > 2 files changed, 129 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/acpi/arm64/mpam.c b/drivers/acpi/arm64/mpam.c > > > index 84963a20c3e7..ca9b8754ae5f 100644 > > > --- a/drivers/acpi/arm64/mpam.c > > > +++ b/drivers/acpi/arm64/mpam.c > > > @@ -220,8 +220,8 @@ static struct platform_device * __init acpi_mpam_parse_msc(struct acpi_mpam_msc_ > > > struct platform_device *pdev __free(platform_device_put) = > > > platform_device_alloc("mpam_msc", tbl_msc->identifier); > > > > Looks like tbl_msc->identifier is getting stashed as pdev->id... > > > > > > > int next_res = 0, next_prop = 0, err; > > > - /* pcc, nrdy, affinity and a sentinel */ > > > - struct property_entry props[4] = { 0 }; > > > + /* pcc, msc-id, nrdy, affinity and a sentinel */ > > > + struct property_entry props[5] = { 0 }; > > > /* mmio, 2xirq, no sentinel. */ > > > struct resource res[3] = { 0 }; > > > struct acpi_device *companion; > > > @@ -256,6 +256,8 @@ static struct platform_device * __init acpi_mpam_parse_msc(struct acpi_mpam_msc_ > > > } else if (iface == MPAM_IFACE_PCC) { > > > props[next_prop++] = PROPERTY_ENTRY_U32("pcc-channel", > > > tbl_msc->base_address); > > > + props[next_prop++] = PROPERTY_ENTRY_U32("msc-id", > > > + tbl_msc->identifier); > > > > Why is this needed then as you can fetch it as pdev->id ? > > I suppose it is to have properties parity between OF and ACPI without > having to change the driver property parsing path. > Yes, that was my initial thought as well. However, after looking into it further, I could not find any device tree bindings in the upstream tree. I am therefore unsure whether MPAM is supported on DT platforms. The use of these device properties appears to have been based on DT bindings that may never have been upstreamed. As [1] suggests, the bindings were dropped before the initial merge. Although we could rename these properties later to align with any DT bindings that are introduced, I think it would be preferable to avoid adding new properties unless they are strictly necessary. -- Regards, Sudeep [1] https://lore.kernel.org/all/20251107123450.664001-1-ben.horgan@arm.com/