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WIP: linux-renesas: kernel 6.18: Fix M.2 SSD issue
Signed-off-by: Yuya Hamamachi <yuya.hamamachi.sx@renesas.com>
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‎recipes-kernel/linux/linux-renesas/0001-PCI-rcar-gen4-Limit-Max_Read_Request_Size-and-Max_Pa.patch‎

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From 91ac4786dac2d028662f3b0f49b3704c55c8eb19 Mon Sep 17 00:00:00 2001
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From: Marek Vasut <marek.vasut+renesas@mailbox.org>
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Date: Sat, 25 Apr 2026 22:17:57 +0200
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Subject: [PATCH] PCI: rcar-gen4: Limit Max_Read_Request_Size and
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Max_Payload_Size to 256 Bytes
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R-Car Gen4 PCIe controller has a hardware limitation of 256 Bytes
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Max_Payload_Size (MPS). PCIe specification indicates that the MPS
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must not exceed minimum MPS of any element along the packet path.
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Force limit Max_Payload_Size to at most 256 Bytes for each device
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connected to this PCIe controller.
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R-Car Gen4 Reference Manual, chapter 104.4.8 Usage notes for
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MRRS (Max Read Request Size) states:
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Please set "Max Read Request Size" to 128 bytes or 256 bytes.
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If "Max Read Request Size" is set to anything other than the
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above, the transferred data will not match the expected value.
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This limitation also seems the apply to devices issuing MRd TLP.
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This limitation can be triggered by using non-HMB NVMe SSD with
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Max_Read_Request_Size 512 Bytes, for example Crucial P5 Plus.
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Any write into the SSD (MRd TLP issued by the SSD) longer than
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256 Bytes wraps around at 256 Byte boundary, and the same data
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are written into the SSD starting at offset 0 and at 256 Bytes.
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Force limit Max_Read_Request_Size to at most 256 Bytes for each
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device connected to this PCIe controller to avoid this behavior.
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An non-HMB (Host Memory Buffer) NVMe SSD can be identified using
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the following command. Affected SSD reports 'hmpre' field as 0:
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"
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$ nvme id-ctrl /dev/nvme0 | grep hmpre
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hmpre : 0
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"
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The symptom is a read from the SSD which wraps around at 256 Byte
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boundary. The test for this symptom can be implemented by writing
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512 Byte of random data into the SSD and reading the data back. If
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the read back data repeat after 256 Bytes, the device is affected.
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"
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$ dd if=/dev/urandom of=/tmp/data.bin bs=256 count=2 \
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dd if=/tmp/data.bin of=/dev/nvme0n1 bs=256 count=2 \
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dd if=/dev/nvme0n1 bs=256 count=2 of=/tmp/readback.bin
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"
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Expected data:
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"
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$ hexdump -vC /tmp/data.bin
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00000000 97 81 b7 3b 0e 38 2b 4d a7 d3 e0 47 ff c2 4b ca
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00000010 c1 85 98 f0 4a ac 03 a0 3b ab f3 19 44 dd 06 8b
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...
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00000100 7a ce 3c b2 e1 d5 d9 11 88 63 10 59 76 3c dc 32 <-- random
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00000110 72 32 2a 7d a3 e1 aa 13 7c da 58 a1 7b 21 11 50 <-- data
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"
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Faulty readback, collected without this change in place:
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"
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$ hexdump -vC /tmp/readback.bin
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00000000 97 81 b7 3b 0e 38 2b 4d a7 d3 e0 47 ff c2 4b ca <---.
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00000010 c1 85 98 f0 4a ac 03 a0 3b ab f3 19 44 dd 06 8b <-. |
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... | |
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00000100 97 81 b7 3b 0e 38 2b 4d a7 d3 e0 47 ff c2 4b ca <-:-+- repeated
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00000110 c1 85 98 f0 4a ac 03 a0 3b ab f3 19 44 dd 06 8b <-+--- data
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^^^
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|
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'--- Repeat starts at offset 0x100 = 256 Bytes
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"
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Upstream-Status: Submitted [https://lore.kernel.org/linux-pci/20260519195219.189323-1-marek.vasut+renesas@mailbox.org/]
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Fixes: 0d0c551011df ("PCI: rcar-gen4: Add R-Car Gen4 PCIe controller support for host mode")
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Cc: stable@vger.kernel.org
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Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
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---
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NOTE: - Possible EP mode limit of 128 Bytes is currently pending
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documentation team input
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V2: - Dispose of the reprogramming of MPS/MRRS altogether
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- Dispose of the entire fixup quirk
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- Replace both with bridge enable_device hook
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- Limit MPS/MRRS along the entire packet path to follow
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MRRS limitation requirement
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---
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drivers/pci/controller/dwc/pcie-rcar-gen4.c | 51 +++++++++++++++++++++
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1 file changed, 51 insertions(+)
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diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
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index 80778917d2ddd..13179d072f89a 100644
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--- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
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+++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
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@@ -305,6 +305,54 @@ static struct rcar_gen4_pcie *rcar_gen4_pcie_alloc(struct platform_device *pdev)
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return rcar;
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}
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+static int rcar_gen4_pcie_enable_device(struct pci_host_bridge *bridge,
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+ struct pci_dev *dev)
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+{
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+ /*
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+ * R-Car Gen4 PCIe controller has a hardware limitation of 256 Bytes
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+ * Max_Payload_Size (MPS). PCIe specification indicates that the MPS
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+ * must not exceed minimum MPS of any element along the packet path.
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+ * Force limit Max_Payload_Size to at most 256 Bytes for each device
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+ * connected to this PCIe controller.
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+ *
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+ * For details, refer to chapter "104.1.1 Features" in either of:
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+ * R-Car S4 R19UH0161EJ0130 Rev.1.30 Jun. 16, 2025 or
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+ * R-Car V4H R19UH0186EJ0130 Rev.1.30 Apr. 21, 2025 or
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+ * R-Car V4M R19UH0217EJ0100 Rev.1.00 Dec. 12, 2025.
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+ */
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+ if (pcie_get_mps(dev) > 256) {
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+ pci_info(dev, "Limiting MPS to 256 bytes\n");
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+ pcie_set_mps(dev, 256);
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+ }
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+
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+ /*
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+ * R-Car Gen4 Reference Manual, chapter 104.4.8 Usage notes for
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+ * MRRS (Max Read Request Size) states:
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+ * Please set "Max Read Request Size" to 128 bytes or 256 bytes.
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+ * If "Max Read Request Size" is set to anything other than the
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+ * above, the transferred data will not match the expected value.
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+ * This limitation also seems the apply to devices issuing MRd TLP.
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+ * This limitation can be triggered by using non-HMB NVMe SSD with
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+ * Max_Read_Request_Size 512 Bytes, for example Crucial P5 Plus.
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+ * Any write into the SSD (MRd TLP issued by the SSD) longer than
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+ * 256 Bytes wraps around at 256 Byte boundary, and the same data
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+ * are written into the SSD starting at offset 0 and at 256 Bytes.
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+ * Force limit Max_Read_Request_Size to at most 256 Bytes for each
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+ * device connected to this PCIe controller to avoid this behavior.
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+ *
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+ * For details, refer to aforementioned chapter in either of:
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+ * R-Car S4 R19UH0161EJ0130 Rev.1.30 Jun. 16, 2025 or
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+ * R-Car V4H R19UH0186EJ0130 Rev.1.30 Apr. 21, 2025 or
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+ * R-Car V4M R19UH0217EJ0100 Rev.1.00 Dec. 12, 2025,
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+ */
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+ if (pcie_get_readrq(dev) > 256) {
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+ pci_info(dev, "Limiting MRRS to 256 bytes\n");
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+ pcie_set_readrq(dev, 256);
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+ }
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+
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+ return 0;
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+}
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+
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/* Host mode */
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static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
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{
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@@ -313,6 +361,9 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
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int ret;
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u32 val;
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+ if (pp->bridge)
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+ pp->bridge->enable_device = rcar_gen4_pcie_enable_device;
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+
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gpiod_set_value_cansleep(dw->pe_rst, 1);
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ret = rcar_gen4_pcie_common_init(rcar);
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--
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2.53.0
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‎recipes-kernel/linux/linux-renesas_6.18.bb‎

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Original file line numberDiff line numberDiff line change
@@ -25,6 +25,7 @@ SRC_URI:append:sparrow-hawk = " \
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file://0001-arm64-dts-renesas-sparrow-hawk-Enable-I2C3-I2C4.patch \
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file://0002-HACK-drivers-gpu-drm-drm_file-Ingnore-flag-checking.patch \
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file://0003-arm64-dts-renesas-r8a779g0-Add-qos-node.patch \
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file://0001-PCI-rcar-gen4-Limit-Max_Read_Request_Size-and-Max_Pa.patch \
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"
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KERNEL_DEVICETREE:append:sparrow-hawk = " \
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renesas/r8a779g3-sparrow-hawk-camera-j1-imx219.dtbo \

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