linux-kernel - Re: [PATCH v3 1/1] dma: actions: Fix lockdep splat for owl-dma

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Date:   Wed, 29 Apr 2020 19:59:23 +0200
From:   Andreas Färber <afaerber@...e.de>
To:     Cristian Ciocaltea <cristian.ciocaltea@...il.com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        dmaengine@...r.kernel.org, linux-actions@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] dma: actions: Fix lockdep splat for owl-dma

Am 29.04.20 um 17:28 schrieb Cristian Ciocaltea:
> When the kernel is built with lockdep support and the owl-dma driver is
> used, the following message is shown:
> 
> [    2.496939] INFO: trying to register non-static key.
> [    2.501889] the code is fine but needs lockdep annotation.
> [    2.507357] turning off the locking correctness validator.
> [    2.512834] CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.3+ #15
> [    2.519084] Hardware name: Generic DT based system
> [    2.523878] Workqueue: events_freezable mmc_rescan
> [    2.528681] [<801127f0>] (unwind_backtrace) from [<8010da58>] (show_stack+0x10/0x14)
> [    2.536420] [<8010da58>] (show_stack) from [<8080fbe8>] (dump_stack+0xb4/0xe0)
> [    2.543645] [<8080fbe8>] (dump_stack) from [<8017efa4>] (register_lock_class+0x6f0/0x718)
> [    2.551816] [<8017efa4>] (register_lock_class) from [<8017b7d0>] (__lock_acquire+0x78/0x25f0)
> [    2.560330] [<8017b7d0>] (__lock_acquire) from [<8017e5e4>] (lock_acquire+0xd8/0x1f4)
> [    2.568159] [<8017e5e4>] (lock_acquire) from [<80831fb0>] (_raw_spin_lock_irqsave+0x3c/0x50)
> [    2.576589] [<80831fb0>] (_raw_spin_lock_irqsave) from [<8051b5fc>] (owl_dma_issue_pending+0xbc/0x120)
> [    2.585884] [<8051b5fc>] (owl_dma_issue_pending) from [<80668cbc>] (owl_mmc_request+0x1b0/0x390)
> [    2.594655] [<80668cbc>] (owl_mmc_request) from [<80650ce0>] (mmc_start_request+0x94/0xbc)
> [    2.602906] [<80650ce0>] (mmc_start_request) from [<80650ec0>] (mmc_wait_for_req+0x64/0xd0)
> [    2.611245] [<80650ec0>] (mmc_wait_for_req) from [<8065aa10>] (mmc_app_send_scr+0x10c/0x144)
> [    2.619669] [<8065aa10>] (mmc_app_send_scr) from [<80659b3c>] (mmc_sd_setup_card+0x4c/0x318)
> [    2.628092] [<80659b3c>] (mmc_sd_setup_card) from [<80659f0c>] (mmc_sd_init_card+0x104/0x430)
> [    2.636601] [<80659f0c>] (mmc_sd_init_card) from [<8065a3e0>] (mmc_attach_sd+0xcc/0x16c)
> [    2.644678] [<8065a3e0>] (mmc_attach_sd) from [<8065301c>] (mmc_rescan+0x3ac/0x40c)
> [    2.652332] [<8065301c>] (mmc_rescan) from [<80143244>] (process_one_work+0x2d8/0x780)
> [    2.660239] [<80143244>] (process_one_work) from [<80143730>] (worker_thread+0x44/0x598)
> [    2.668323] [<80143730>] (worker_thread) from [<8014b5f8>] (kthread+0x148/0x150)
> [    2.675708] [<8014b5f8>] (kthread) from [<801010b4>] (ret_from_fork+0x14/0x20)
> [    2.682912] Exception stack(0xee8fdfb0 to 0xee8fdff8)
> [    2.687954] dfa0:                                     00000000 00000000 00000000 00000000
> [    2.696118] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [    2.704277] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> 
> The obvious fix would be to use 'spin_lock_init()' on 'pchan->lock'
> before attempting to call 'spin_lock_irqsave()' in 'owl_dma_get_pchan()'.
> 
> However, according to Manivannan Sadhasivam, 'pchan->lock' was supposed
> to only protect 'pchan->vchan' while 'od->lock' does a similar job in
> 'owl_dma_terminate_pchan'.
> 
> Therefore, this patch will simply substitute 'pchan->lock' with 'od->lock'
> and removes the 'lock' attribute in 'owl_dma_pchan' struct.
> 

Please add:

Fixes: 47e20577c24d ("dmaengine: Add Actions Semi Owl family S900 DMA 
driver")

> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...il.com>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
> Changes in v3:
> * Get rid of the kerneldoc comment for the removed struct attribute
> * Add the Reviewed-by tag in the commit message
> 
> Changes in v2:
> * Improve the fix as suggested by Manivannan Sadhasivam: substitute
>    'pchan->lock' with 'od->lock' and get rid of the 'lock' attribute in
>    'owl_dma_pchan' struct
> * Update the commit message to reflect the changes
> 
>   drivers/dma/owl-dma.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)

Otherwise no objections from my side,

Acked-by: Andreas Färber <afaerber@...e.de>

Maybe the DMA maintainers can add those two lines when picking it up, to 
avoid a v4?

Regards,
Andreas

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