From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590120; b=PPyDPRSbBic3kdIBFi75nOlv6i0itqAx9iXg8ppRUvCoFM7KO07m2wagBXBeCm9AD1cb 1ynrflcC4vM6U77RJc9k+/bgmzL3yf0feei1Bdgvv06FdU/dZ+5yPS8dfcBzG8n0JQy5/ bli/4pC74h+fmNekjZiEGuPd1PhhoV+uuO7lLuNuNh2Hs+90Pto00RJxeYawjyKesxTmY Vq8bzeqjiEPu+comvJwbiVvrKWMyC4Djty5U2Ka9UaTYsqRYP3Ypggjgo0NBg5SUvwdCx ikjbfnv9kkvDLTS2AUiAT8oL04ShoMYItqy+Y6P1ExU/OOSSmcLSsbcyWIJZZAfPMtg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590120; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=tDocmy1IeVSFKxeoKKCbdgyST5OHq5grxFPE4/CF9fs=; b=RKoO2S0LlcmlYaeI8cfeoPaU4XBNeFKNPIiZM/SIjlqTehhPRcL3Qv/Vnd6oMhX1kAzy p58deIJqiMs8Q051a95VrwIFpOsB743ZocL20a3HbGfbylZiqw7XCel8/rwb9/MwIKyZo cJPTUZLFLQf1A0T9gCcPr7sTxTg49zTmPQXP8nLi8PrC34IcRQO4sYZCGHcinAGk53PQG fdR2unPXnZrpcJNbbX1eFphmpZY2KFgiaAinnzyonTwBqwUwGsBmrjKie/Fq/dKea7L7L qvRKIoNOO9HN8W962SGoqruu1dQ4oSwCGNONGXjtigg/iIfWRbBUwZgwaKQUCD33CiQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=eGGN15UD; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90C9C606B22C; Fri, 13 Nov 2026 17:15:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=eGGN15UD Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D58B1F000C6; Fri, 13 Nov 2026 17:15:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590120; bh=tDocmy1IeVSFKxeoKKCbdgyST5OHq5grxFPE4/CF9fs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=eGGN15UDWa9IOmZ5DFxEPi8XdSd/FgmFj6IeWvD4OvImq37PqBMikPKFo1g/AxTVv cM1omAOhpF2CWPQSNHlTed2T2qHDA8NMtfqICBVoPIMWPSGVzP2cBJ0p7vWS08DKXd z/Fy90pG+mwjfd2kWAsdZqYhyVSvEViPKxIKi6Wc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Marek Vasut , Manivannan Sadhasivam , Bjorn Helgaas , Sasha Levin Subject: [PATCH 6.18 097/686] PCI: rcar-gen4: Limit Max_Read_Request_Size to 256 Bytes Date: Fri, 13 Nov 2026 10:43:50 -0500 Message-ID: <20261113153824.152061826@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Marek Vasut [ Upstream commit f0a5c6bd797c2b9900034983a1118d27eb2f2f16 ] R-Car Gen4 PCIe controller has a hardware limitation of 256 Bytes Max_Payload_Size (MPS). PCIe specification indicates that the MPS must not exceed minimum MPS of any element along the packet path. The PCI core already enforces this, but add a check to warn if MPS is ever set larger than 256. R-Car Gen4 Reference Manual, chapter 104.4.8 Usage notes for MRRS (Max Read Request Size) states: Please set "Max Read Request Size" to 128 bytes or 256 bytes. If "Max Read Request Size" is set to anything other than the above, the transferred data will not match the expected value. This limitation also seems to apply to devices doing DMA reads, i.e., issuing MRd TLPs. This limitation can be triggered by using non-HMB NVMe SSD with Max_Read_Request_Size 512 Bytes, for example Crucial P5 Plus. Any write to the SSD (MRd TLP issued by the SSD controller) longer than 256 Bytes wraps around at the 256 Byte boundary, and the same data are written to the SSD starting at offset 0 and at 256 Bytes. Limit Max_Read_Request_Size to at most 256 Bytes for each device connected to this PCIe controller to avoid this behavior. A non-HMB (Host Memory Buffer) NVMe SSD can be identified using the following command. Affected SSD reports 'hmpre' field as 0: $ nvme id-ctrl /dev/nvme0 | grep hmpre hmpre : 0 The symptom is a read from the SSD which wraps around at 256 Byte boundary. The test for this symptom can be implemented by writing 512 Byte of random data into the SSD and reading the data back. If the read back data repeat after 256 Bytes, the device is affected. $ dd if=/dev/urandom of=/tmp/data.bin bs=256 count=2 ; \ dd if=/tmp/data.bin of=/dev/nvme0n1 bs=256 count=2 ; \ dd if=/dev/nvme0n1 bs=256 count=2 of=/tmp/readback.bin Expected data: $ hexdump -vC /tmp/data.bin 00000000 97 81 b7 3b 0e 38 2b 4d a7 d3 e0 47 ff c2 4b ca 00000010 c1 85 98 f0 4a ac 03 a0 3b ab f3 19 44 dd 06 8b ... 00000100 7a ce 3c b2 e1 d5 d9 11 88 63 10 59 76 3c dc 32 <-- random 00000110 72 32 2a 7d a3 e1 aa 13 7c da 58 a1 7b 21 11 50 <-- data Faulty readback, collected without this change in place: $ hexdump -vC /tmp/readback.bin 00000000 97 81 b7 3b 0e 38 2b 4d a7 d3 e0 47 ff c2 4b ca <---. 00000010 c1 85 98 f0 4a ac 03 a0 3b ab f3 19 44 dd 06 8b <-. | ... | | 00000100 97 81 b7 3b 0e 38 2b 4d a7 d3 e0 47 ff c2 4b ca <-:-+- repeated 00000110 c1 85 98 f0 4a ac 03 a0 3b ab f3 19 44 dd 06 8b <-+--- data ^^^ | '--- Repeat starts at offset 0x100 = 256 Bytes Fixes: 0d0c551011df ("PCI: rcar-gen4: Add R-Car Gen4 PCIe controller support for host mode") Signed-off-by: Marek Vasut Signed-off-by: Manivannan Sadhasivam Signed-off-by: Bjorn Helgaas Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260821020636.111719-1-marek.vasut+renesas@mailbox.org Signed-off-by: Sasha Levin --- drivers/pci/controller/dwc/pcie-rcar-gen4.c | 54 +++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c index 7e171526b1ded..9e5dc1009ed4e 100644 --- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c +++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c @@ -305,6 +305,57 @@ static struct rcar_gen4_pcie *rcar_gen4_pcie_alloc(struct platform_device *pdev) return rcar; } +static int rcar_gen4_pcie_enable_device(struct pci_host_bridge *bridge, + struct pci_dev *dev) +{ + /* + * R-Car Gen4 PCIe controller has a hardware limitation of 256 Bytes + * Max_Payload_Size (MPS). PCIe specification indicates that the MPS + * must not exceed minimum MPS of any element along the packet path. + * The controller reports Max_Payload_Size_Supported (MPSS) 256 Bytes + * for header type 0 and 128 Bytes for header type 1. The PCIe core + * will not allow MPS to be set higher than MPSS; warn here in case + * something went very wrong in the core. + * + * For details, refer to chapter "104.1.1 Features" in either of: + * R-Car S4 R19UH0161EJ0140 Rev.1.40 Jul. 31, 2026 or + * R-Car V4H R19UH0186EJ0140 Rev.1.40 Aug. 7, 2026 or + * R-Car V4M R19UH0217EJ0110 Rev.1.10 Jun. 30, 2026. + */ + WARN_ON(pcie_get_mps(dev) > 256); + + /* + * R-Car Gen4 Reference Manual, chapter 104.4.8 Usage notes for + * MRRS (Max Read Request Size) states: + * + * Please set "Max Read Request Size" to 128 bytes or 256 bytes. + * If "Max Read Request Size" is set to anything other than the + * above, the transferred data will not match the expected value. + * + * This limitation also seems to apply to devices issuing MRd TLPs. + * This limitation can be triggered by using non-HMB NVMe SSD with + * Max_Read_Request_Size 512 Bytes, for example Crucial P5 Plus. + * Any write into the SSD (MRd TLP issued by the SSD) longer than + * 256 Bytes wraps around at 256 Byte boundary, and the same data + * are written into the SSD starting at offset 0 and at 256 Bytes. + * + * Limit Max_Read_Request_Size to at most 256 Bytes for each + * device connected to this PCIe controller to avoid this behavior. + * + * For details, refer to aforementioned chapter in either of: + * R-Car S4 R19UH0161EJ0140 Rev.1.40 Jul. 31, 2026 or + * R-Car V4H R19UH0186EJ0140 Rev.1.40 Aug. 7, 2026 or + * R-Car V4M R19UH0217EJ0110 Rev.1.10 Jun. 30, 2026. + */ + bridge->no_inc_mrrs = 1; + if (pcie_get_readrq(dev) > 256) { + pci_info(dev, "Limiting MRRS to 256 bytes\n"); + pcie_set_readrq(dev, 256); + } + + return 0; +} + /* Host mode */ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp) { @@ -313,6 +364,9 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp) int ret; u32 val; + if (pp->bridge) + pp->bridge->enable_device = rcar_gen4_pcie_enable_device; + gpiod_set_value_cansleep(dw->pe_rst, 1); ret = rcar_gen4_pcie_common_init(rcar); -- 2.53.0