linux-kernel - Re: [PATCH v2 RESEND 2/2] dmaengine: tegra210-adma: Support channel page

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Message-ID: <0f1df4ea-0b31-4431-b538-09dbd27845d8@nvidia.com>
Date: Mon, 20 Jan 2025 09:16:07 +0530
From: Mohan Kumar D <mkumard@...dia.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: vkoul@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
 linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
 treding@...dia.com, jonathanh@...dia.com, spujar@...dia.com
Subject: Re: [PATCH v2 RESEND 2/2] dmaengine: tegra210-adma: Support channel
 page


On 18-01-2025 22:03, Guenter Roeck wrote:
> External email: Use caution opening links or attachments
>
>
> Hi,
>
> On Tue, Dec 17, 2024 at 01:13:58PM +0530, Mohan Kumar D wrote:
>> Multiple ADMA Channel page hardware support has been
>> added from TEGRA186 and onwards.
>>
>> - Add support in the tegra adma driver to handle selective
>>    channel page usage
>> - Make global register programming optional
>>
>> Signed-off-by: Mohan Kumar D <mkumard@...dia.com>
> This patch triggers a build failure when trying to build i386:all{yes,mod}config.
>
> x86_64-linux-ld: drivers/dma/tegra210-adma.o: in function `tegra_adma_probe':
> tegra210-adma.c:(.text+0x1322): undefined reference to `__udivdi3'
>
> Bisect log is attached for reference.
>
> Problem is
>
>> +             if (res_base) {
>> +                     page_no = (res_page->start - res_base->start) / cdata->ch_base_offset;
> ->start is phys_addr_t which can be a 64-bit pointer on 32-bit systems,
> making this a 64-bit divide operation.
>
> Bisect log and a possible fix are attached for reference. I am not sure
> though if the suggested fix is correct/complete since page_no might
> overflow on such systems. It should possibly be a phys_addr_t, but that
> is unsigned so the subsequent negative check would not work.
>
> Guenter
https://lore.kernel.org/lkml/20250116162033.3922252-1-mkumard@nvidia.com/T/ 
has been pushed recently to fix this issue. Can you please consider this 
patch series.
>
> ---
> # bad: [0907e7fb35756464aa34c35d6abb02998418164b] Add linux-next specific files for 20250117
> # good: [5bc55a333a2f7316b58edc7573e8e893f7acb532] Linux 6.13-rc7
> git bisect start 'HEAD' 'v6.13-rc7'
> # good: [195cedf4deacf84167c32b866ceac1cf4a16df15] Merge branch 'main' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
> git bisect good 195cedf4deacf84167c32b866ceac1cf4a16df15
> # good: [01c19ecf34e1713365346f932011facd7d2d2bc6] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply.git
> git bisect good 01c19ecf34e1713365346f932011facd7d2d2bc6
> # good: [7fac8eef32d7735a3b01d08f2c98d5e6eaf254da] Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
> git bisect good 7fac8eef32d7735a3b01d08f2c98d5e6eaf254da
> # bad: [24c55da105e9a641fa77c8d8efbf92472a18bf4e] Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine.git
> git bisect bad 24c55da105e9a641fa77c8d8efbf92472a18bf4e
> # good: [73656a6ab6d428102eb5aaa9599b5fcba4a2501f] intel_th: core: fix kernel-doc warnings
> git bisect good 73656a6ab6d428102eb5aaa9599b5fcba4a2501f
> # good: [b995a104a0aa1d6b90ea4ba3110e657ae9e83213] Merge branch 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
> git bisect good b995a104a0aa1d6b90ea4ba3110e657ae9e83213
> # good: [002c855847f718e12879808404dc8375207012dd] Merge branch 'next' of git://github.com/awilliam/linux-vfio.git
> git bisect good 002c855847f718e12879808404dc8375207012dd
> # bad: [54e09c8e2d3b0b7d603a64368fa49fe2a8031dd1] dt-bindings: dma: st-stm32-dmamux: Add description for dma-cell values
> git bisect bad 54e09c8e2d3b0b7d603a64368fa49fe2a8031dd1
> # good: [9d880452fb3edc4645e28264381ce35606fb1b19] dmaengine: amd: qdma: make read-only arrays h2c_types and c2h_types static const
> git bisect good 9d880452fb3edc4645e28264381ce35606fb1b19
> # good: [775363772f5e72b984a883e22d510fec5357477a] dt-bindings: dma: ti: k3-bcdma: Add J722S CSI BCDMA
> git bisect good 775363772f5e72b984a883e22d510fec5357477a
> # bad: [36d8cbd661c48f4c18eeb414146ec68a71fd644f] Merge branch 'fixes' into next
> git bisect bad 36d8cbd661c48f4c18eeb414146ec68a71fd644f
> # good: [762b37fc6ae2af0c7ddf36556fe7427575e9c759] dt-bindings: dma: Support channel page to nvidia,tegra210-adma
> git bisect good 762b37fc6ae2af0c7ddf36556fe7427575e9c759
> # bad: [9602a843cb3a16df8930eb9b046aa7aeb769521b] dmaengine: bcm2835-dma: Prevent suspend if DMA channel is busy
> git bisect bad 9602a843cb3a16df8930eb9b046aa7aeb769521b
> # bad: [68811c928f88828f188656dd3c9c184eeec2ce86] dmaengine: tegra210-adma: Support channel page
> git bisect bad 68811c928f88828f188656dd3c9c184eeec2ce86
> # first bad commit: [68811c928f88828f188656dd3c9c184eeec2ce86] dmaengine: tegra210-adma: Support channel page
>
> ---
> diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c
> index 6896da8ac7ef..1de3d84d3b7c 100644
> --- a/drivers/dma/tegra210-adma.c
> +++ b/drivers/dma/tegra210-adma.c
> @@ -914,7 +914,7 @@ static int tegra_adma_probe(struct platform_device *pdev)
>
>                  res_base = platform_get_resource_byname(pdev, IORESOURCE_MEM, "global");
>                  if (res_base) {
> -                       page_no = (res_page->start - res_base->start) / cdata->ch_base_offset;
> +                       page_no = div_s64(res_page->start - res_base->start, cdata->ch_base_offset);
>                          if (page_no <= 0)
>                                  return -EINVAL;
>                          tdma->ch_page_no = page_no - 1;