linux-kernel - Re: [PATCH v2] dmaengine: xilinx: xdma: Fix regmap max

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Message-ID: <318ba0b9-a730-15b1-7573-db23c2cd9e32@amd.com>
Date: Tue, 2 Sep 2025 09:46:22 -0700
From: Lizhi Hou <lizhi.hou@....com>
To: <anthony@...rulasolutions.com>, Brian Xu <brian.xu@....com>, "Raj Kumar
 Rampelli" <raj.kumar.rampelli@....com>, Vinod Koul <vkoul@...nel.org>, Michal
 Simek <michal.simek@....com>
CC: <dmaengine@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] dmaengine: xilinx: xdma: Fix regmap max_register

Forgot to mention that it needs a 'Fixes:' tag.

On 9/2/25 09:42, Lizhi Hou wrote:
> Reviewed-by: Lizhi Hou <lizhi.hou@....com>
>
> On 9/1/25 14:30, Anthony Brandon via B4 Relay wrote:
>> From: Anthony Brandon <anthony@...rulasolutions.com>
>>
>> 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
>>
>> Signed-off-by: Anthony Brandon <anthony@...rulasolutions.com>
>> ---
>> Changes in v2:
>> - Define new constant XDMA_MAX_REG_OFFSET and use that.
>> - Link to v1: 
>> https://lore.kernel.org/r/20250901-xdma-max-reg-v1-1-b6a04561edb1@amarulasolutions.com
>> ---
>>   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 
>> 6ad08878e93862b770febb71b8bc85e66813428e..70bca92621aa41b0367d1e236b3e276344a26320 
>> 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 
>> 0d88b1a670e142dac90d09c515809faa2476a816..5ecf8223c112e468c79ce635398ba393a535b9e0 
>> 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,
>>   };
>>     /**
>>
>> ---
>> base-commit: b320789d6883cc00ac78ce83bccbfe7ed58afcf0
>> change-id: 20250901-xdma-max-reg-1649c6459358
>>
>> Best regards,