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b=TPpBNrq33nZD2w6VH6KdW1t5xl2b3XOS88g2QrbkIjafnzRii9roIh0V6okNVhYMmayKs32GVE7TELF9DsHOpiYa2HS8Ab4tXKSkwHrsKd2kTy1JsYcqGEWbsalJHhAZ+Wddep2X0uajCWh6MI8OhshhHPmzGH2ohKl7Jk5IFbo= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DM6PR12MB4202.namprd12.prod.outlook.com (2603:10b6:5:219::22) by BL3PR12MB6594.namprd12.prod.outlook.com (2603:10b6:208:38d::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7897.27; Wed, 28 Aug 2024 13:43:53 +0000 Received: from DM6PR12MB4202.namprd12.prod.outlook.com ([fe80::f943:600c:2558:af79]) by DM6PR12MB4202.namprd12.prod.outlook.com ([fe80::f943:600c:2558:af79%4]) with mapi id 15.20.7897.027; Wed, 28 Aug 2024 13:43:52 +0000 Message-ID: <301642a1-ae97-7140-3b52-da0e6e69e7c7@amd.com> Date: Wed, 28 Aug 2024 14:43:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v2 08/15] cxl: indicate probe deferral Content-Language: en-US To: Zhi Wang , alejandro.lucero-palau@amd.com Cc: linux-cxl@vger.kernel.org, netdev@vger.kernel.org, dan.j.williams@intel.com, martin.habets@xilinx.com, edward.cree@amd.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, richard.hughes@amd.com, targupta@nvidia.com, vsethi@nvidia.com References: <20240715172835.24757-1-alejandro.lucero-palau@amd.com> <20240715172835.24757-9-alejandro.lucero-palau@amd.com> <20240826204232.000009ce.zhiw@nvidia.com> From: Alejandro Lucero Palau In-Reply-To: <20240826204232.000009ce.zhiw@nvidia.com> Content-Type: text/plain; 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That kicks >> off cxl_mem_probe() to enumerate all 'struct cxl_port' instances in >> the topology up to the root. >> >> If the root driver has not attached yet the expectation is that the >> driver waits until that link is established. The common cxl_pci_driver >> has reason to keep the 'struct cxl_memdev' device attached to the bus >> until the root driver attaches. An accelerator may want to instead >> defer probing until CXL resources can be acquired. >> >> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when >> accelerator driver probing should be defferred vs failed. Provide that >> indication via a new cxl_acquire_endpoint() API that can retrieve the >> probe status of the memdev. >> >> The first consumer of this API is a test driver that excercises the >> CXL Type-2 flow. >> > Out of curiosity, when and where do we probe CXL_DVSEC_CACHE_CAPABLE and > enable the CXL_DVSEC_CACHE_ENABLE bit for a type-2 device? > > Thanks, > Zhi. As It is mentioned in the cover letter, this is a Type2 device but not working on CXL.cache yet. I hope we can discuss how to deal with CXL.cache in the LPC next month. I'll be talking about it and current state of this patchset. Thank you >> Based on >> https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2 >> >> Signed-off-by: Alejandro Lucero >> Co-developed-by: Dan Williams >> --- >> drivers/cxl/core/memdev.c | 41 >> ++++++++++++++++++++++++++++++ drivers/cxl/core/port.c | >> 2 +- drivers/cxl/mem.c | 7 +++-- >> drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++- >> include/linux/cxl_accel_mem.h | 3 +++ >> 5 files changed, 59 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c >> index b902948b121f..d51c8bfb32e3 100644 >> --- a/drivers/cxl/core/memdev.c >> +++ b/drivers/cxl/core/memdev.c >> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct >> device *host, } >> EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL); >> >> +/* >> + * Try to get a locked reference on a memdev's CXL port topology >> + * connection. Be careful to observe when cxl_mem_probe() has >> deposited >> + * a probe deferral awaiting the arrival of the CXL root driver >> +*/ >> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd) >> +{ >> + struct cxl_port *endpoint; >> + int rc = -ENXIO; >> + >> + device_lock(&cxlmd->dev); >> + endpoint = cxlmd->endpoint; >> + if (!endpoint) >> + goto err; >> + >> + if (IS_ERR(endpoint)) { >> + rc = PTR_ERR(endpoint); >> + goto err; >> + } >> + >> + device_lock(&endpoint->dev); >> + if (!endpoint->dev.driver) >> + goto err_endpoint; >> + >> + return endpoint; >> + >> +err_endpoint: >> + device_unlock(&endpoint->dev); >> +err: >> + device_unlock(&cxlmd->dev); >> + return ERR_PTR(rc); >> +} >> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL); >> + >> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port >> *endpoint) +{ >> + device_unlock(&endpoint->dev); >> + device_unlock(&cxlmd->dev); >> +} >> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL); >> + >> static void sanitize_teardown_notifier(void *data) >> { >> struct cxl_memdev_state *mds = data; >> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c >> index d66c6349ed2d..3c6b896c5f65 100644 >> --- a/drivers/cxl/core/port.c >> +++ b/drivers/cxl/core/port.c >> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev >> *cxlmd, */ >> dev_dbg(&cxlmd->dev, "%s is a root dport\n", >> dev_name(dport_dev)); >> - return -ENXIO; >> + return -EPROBE_DEFER; >> } >> >> parent_port = find_cxl_port(dparent, &parent_dport); >> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c >> index f76af75a87b7..383a6f4829d3 100644 >> --- a/drivers/cxl/mem.c >> +++ b/drivers/cxl/mem.c >> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev) >> return rc; >> >> rc = devm_cxl_enumerate_ports(cxlmd); >> - if (rc) >> + if (rc) { >> + cxlmd->endpoint = ERR_PTR(rc); >> return rc; >> + } >> >> parent_port = cxl_mem_find_port(cxlmd, &dport); >> if (!parent_port) { >> dev_err(dev, "CXL port topology not found\n"); >> - return -ENXIO; >> + cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER); >> + return -EPROBE_DEFER; >> } >> >> if (resource_size(&cxlds->pmem_res) && >> IS_ENABLED(CONFIG_CXL_PMEM)) { diff --git >> a/drivers/net/ethernet/sfc/efx_cxl.c >> b/drivers/net/ethernet/sfc/efx_cxl.c index 0abe66490ef5..2cf4837ddfc1 >> 100644 --- a/drivers/net/ethernet/sfc/efx_cxl.c +++ >> b/drivers/net/ethernet/sfc/efx_cxl.c @@ -65,8 +65,16 @@ void >> efx_cxl_init(struct efx_nic *efx) } >> >> cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds); >> - if (IS_ERR(cxl->cxlmd)) >> + if (IS_ERR(cxl->cxlmd)) { >> pci_info(pci_dev, "CXL accel memdev creation >> failed"); >> + return; >> + } >> + >> + cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd); >> + if (IS_ERR(cxl->endpoint)) >> + pci_info(pci_dev, "CXL accel acquire endpoint >> failed"); + >> + cxl_release_endpoint(cxl->cxlmd, cxl->endpoint); >> } >> >> >> diff --git a/include/linux/cxl_accel_mem.h >> b/include/linux/cxl_accel_mem.h index 442ed9862292..701910021df8 >> 100644 --- a/include/linux/cxl_accel_mem.h >> +++ b/include/linux/cxl_accel_mem.h >> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state >> *cxlds); >> struct cxl_memdev *devm_cxl_add_memdev(struct device *host, >> struct cxl_dev_state *cxlds); >> + >> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd); >> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port >> *endpoint); #endif