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

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Message-ID:
 <DS7PR12MB59581DE67ECA59637F73D4F9B707A@DS7PR12MB5958.namprd12.prod.outlook.com>
Date: Mon, 1 Sep 2025 16:37:52 +0000
From: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
To: "anthony@...rulasolutions.com" <anthony@...rulasolutions.com>, "Hou,
 Lizhi" <lizhi.hou@....com>, "Xu, Brian" <brian.xu@....com>, "Rampelli, Raj
 Kumar" <raj.kumar.rampelli@....com>, Vinod Koul <vkoul@...nel.org>, "Simek,
 Michal" <michal.simek@....com>
CC: "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] dmaengine: xilinx: xdma: Fix regmap max_register

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Anthony Brandon via B4 Relay
> <devnull+anthony.amarulasolutions.com@...nel.org>
> Sent: Monday, September 1, 2025 5:07 PM
> To: Hou, Lizhi <lizhi.hou@....com>; Xu, Brian <brian.xu@....com>; Rampelli,
> Raj Kumar <raj.kumar.rampelli@....com>; Vinod Koul <vkoul@...nel.org>; Simek,
> Michal <michal.simek@....com>
> Cc: dmaengine@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; Anthony Brandon <anthony@...rulasolutions.com>
> Subject: [PATCH] dmaengine: xilinx: xdma: Fix regmap max_register
>
> 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>
> ---
>  drivers/dma/xilinx/xdma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c index
> 0d88b1a670e142dac90d09c515809faa2476a816..cb73801fd6cf91fc420d6a8ab0c97
> 3dcdb5772f5 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_REG_SPACE_LEN - 4,

Nit - Better to change the value of #define itself and we can rename
it to XDMA_MAX_REG_OFFSET?

Will wait for Lizhi and Brain to confirm if XDMA_REG_SPACE_LEN - 4
is highest valid register address as per IP documentation,

>  };
>
>  /**
>
> ---
> base-commit: b320789d6883cc00ac78ce83bccbfe7ed58afcf0
> change-id: 20250901-xdma-max-reg-1649c6459358
>
> Best regards,
> --
> Anthony Brandon <anthony@...rulasolutions.com>
>
>