[PATCH 6.6 032/254] dmaengine: xilinx: xdma: Fix regmap max_register

Greg Kroah-Hartman
2026-01-28T15:28:12Z

From: Anthony Brandon <anthony@amarulasolutions.com>

[ Upstream commit c7d436a6c1a274c1ac28d5fb3b8eb8f03b6d0e10 ]

The max_register field is assigned the size of the register memory
region instead of the offset of the last register.
The result is that reading from the regmap via debugfs can cause
a segmentation fault:

tail /sys/kernel/debug/regmap/xdma.1.auto/registers
Unable to handle kernel paging request at virtual address ffff800082f70000
Mem abort info:
ESR = 0x0000000096000007
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x07: level 3 translation fault
[...]
Call trace:
regmap_mmio_read32le+0x10/0x30
_regmap_bus_reg_read+0x74/0xc0
_regmap_read+0x68/0x198
regmap_read+0x54/0x88
regmap_read_debugfs+0x140/0x380
regmap_map_read_file+0x30/0x48
full_proxy_read+0x68/0xc8
vfs_read+0xcc/0x310
ksys_read+0x7c/0x120
__arm64_sys_read+0x24/0x40
invoke_syscall.constprop.0+0x64/0x108
do_el0_svc+0xb0/0xd8
el0_svc+0x38/0x130
el0t_64_sync_handler+0x120/0x138
el0t_64_sync+0x194/0x198
Code: aa1e03e9 d503201f f9400000 8b214000 (b9400000)
---[ end trace 0000000000000000 ]---
note: tail[1217] exited with irqs disabled
note: tail[1217] exited with preempt_count 1
Segmentation fault

Fixes: 17ce252266c7 ("dmaengine: xilinx: xdma: Add xilinx xdma driver")
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Anthony Brandon <anthony@amarulasolutions.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/xilinx/xdma-regs.h | 1 +
drivers/dma/xilinx/xdma.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/xilinx/xdma-regs.h b/drivers/dma/xilinx/xdma-regs.h
index dd98b4526b90a..b19c173d8bfce 100644
--- a/drivers/dma/xilinx/xdma-regs.h
+++ b/drivers/dma/xilinx/xdma-regs.h
@@ -9,6 +9,7 @@

/* The length of register space exposed to host */
#define XDMA_REG_SPACE_LEN 65536
+#define XDMA_MAX_REG_OFFSET (XDMA_REG_SPACE_LEN - 4)

/*
* maximum number of DMA channels for each direction:
diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
index e0bfd129d563f..dbab4c4499143 100644
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -38,7 +38,7 @@ static const struct regmap_config xdma_regmap_config = {
.reg_bits = 32,
.val_bits = 32,
.reg_stride = 4,
- .max_register = XDMA_REG_SPACE_LEN,
+ .max_register = XDMA_MAX_REG_OFFSET,
};

/**
--
2.51.0