linux-kernel - Re: [PATCH v2 1/3] bus: mhi: host: keep bhi buffer through suspend cycle

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Message-ID: <05afc25c-f5ab-4382-8b66-c47a6ea2fa2f@oss.qualcomm.com>
Date: Wed, 16 Jul 2025 11:41:11 +0800
From: Baochen Qiang <baochen.qiang@....qualcomm.com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Jeff Hugo <jeff.hugo@....qualcomm.com>,
        Youssef Samir <quic_yabdulra@...cinc.com>,
        Matthew Leung <quic_mattleun@...cinc.com>,
        Alexander Wilhelm <alexander.wilhelm@...termo.com>,
        Kunwu Chan <chentao@...inos.cn>,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
        Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
        Yan Zhen <yanzhen@...o.com>, Sujeev Dias <sdias@...eaurora.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Siddartha Mohanadoss <smohanad@...eaurora.org>, mhi@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: kernel@...labora.com, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/3] bus: mhi: host: keep bhi buffer through suspend
 cycle



On 7/15/2025 9:25 PM, Muhammad Usama Anjum wrote:
> When there is memory pressure, at resume time dma_alloc_coherent()
> returns error which in turn fails the loading of firmware and hence
> the driver crashes:
> 
> kernel: kworker/u33:5: page allocation failure: order:7,
> mode:0xc04(GFP_NOIO|GFP_DMA32), nodemask=(null),cpuset=/,mems_allowed=0
> kernel: CPU: 1 UID: 0 PID: 7693 Comm: kworker/u33:5 Not tainted 6.11.11-valve17-1-neptune-611-g027868a0ac03 #1 3843143b92e9da0fa2d3d5f21f51beaed15c7d59
> kernel: Hardware name: Valve Galileo/Galileo, BIOS F7G0112 08/01/2024
> kernel: Workqueue: mhi_hiprio_wq mhi_pm_st_worker [mhi]
> kernel: Call Trace:
> kernel:  <TASK>
> kernel:  dump_stack_lvl+0x4e/0x70
> kernel:  warn_alloc+0x164/0x190
> kernel:  ? srso_return_thunk+0x5/0x5f
> kernel:  ? __alloc_pages_direct_compact+0xaf/0x360
> kernel:  __alloc_pages_slowpath.constprop.0+0xc75/0xd70
> kernel:  __alloc_pages_noprof+0x321/0x350
> kernel:  __dma_direct_alloc_pages.isra.0+0x14a/0x290
> kernel:  dma_direct_alloc+0x70/0x270
> kernel:  mhi_fw_load_handler+0x126/0x340 [mhi a96cb91daba500cc77f86bad60c1f332dc3babdf]
> kernel:  mhi_pm_st_worker+0x5e8/0xac0 [mhi a96cb91daba500cc77f86bad60c1f332dc3babdf]
> kernel:  ? srso_return_thunk+0x5/0x5f
> kernel:  process_one_work+0x17e/0x330
> kernel:  worker_thread+0x2ce/0x3f0
> kernel:  ? __pfx_worker_thread+0x10/0x10
> kernel:  kthread+0xd2/0x100
> kernel:  ? __pfx_kthread+0x10/0x10
> kernel:  ret_from_fork+0x34/0x50
> kernel:  ? __pfx_kthread+0x10/0x10
> kernel:  ret_from_fork_asm+0x1a/0x30
> kernel:  </TASK>
> kernel: Mem-Info:
> kernel: active_anon:513809 inactive_anon:152 isolated_anon:0
>     active_file:359315 inactive_file:2487001 isolated_file:0
>     unevictable:637 dirty:19 writeback:0
>     slab_reclaimable:160391 slab_unreclaimable:39729
>     mapped:175836 shmem:51039 pagetables:4415
>     sec_pagetables:0 bounce:0
>     kernel_misc_reclaimable:0
>     free:125666 free_pcp:0 free_cma:0
> 
> In above example, if we sum all the consumed memory, it comes out
> to be 15.5GB and free memory is ~ 500MB from a total of 16GB RAM.
> Even though memory is present. But all of the dma memory has been
> exhausted or fragmented.
> 
> Fix it by allocating it only once and then reuse the same allocated
> memory. As we'll allocate this memory only once, this memory will stay
> allocated.

BHI buffer is not needed anymore after initial firmware loaded. So IMO we can not keep it
just for the purpose of avoiding OOM in the future.