linux-kernel - Re: [PATCH] media: mtk-vcodec: set dma max segment size

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Message-ID: <f8c5b7e0-66a2-7ec6-041f-82679a863758@arm.com>
Date:   Wed, 2 Sep 2020 15:25:27 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Hsin-Yi Wang <hsinyi@...omium.org>,
        linux-mediatek@...ts.infradead.org
Cc:     Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        Irui Wang <irui.wang@...iatek.com>,
        linux-kernel@...r.kernel.org,
        Anand K Mistry <amistry@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [PATCH] media: mtk-vcodec: set dma max segment size

On 2020-08-21 05:14, Hsin-Yi Wang wrote:
> Set dma max segment size for encoder and decoder driver.
> 
> Fix following warning with CONFIG_DMA_API_DEBUG_SG=y
> 
> [   75.147825] ------------[ cut here ]------------
> [   75.147844] mtk-vcodec-enc 19002000.vcodec: DMA-API: mapping sg segment longer than device claims to support [len=983040] [max=65536]
> [   75.147876] WARNING: CPU: 2 PID: 4069 at kernel/dma/debug.c:1302 debug_dma_map_sg+0x1a8/0x2c4
> ...
> [   75.148139] Call trace:
> [   75.148149]  debug_dma_map_sg+0x1a8/0x2c4
> [   75.148165]  vb2_dc_get_userptr+0x228/0x364 [videobuf2_dma_contig]
> [   75.148178]  __buf_prepare+0x3ac/0x8c0 [videobuf2_common]
> [   75.148188]  vb2_core_qbuf+0xa4/0x58c [videobuf2_common]
> [   75.148199]  vb2_qbuf+0x88/0xe4 [videobuf2_v4l2]
> [   75.148211]  v4l2_m2m_qbuf+0x80/0xf8 [v4l2_mem2mem]
> [   75.148221]  vidioc_venc_qbuf+0x3c/0x70 [mtk_vcodec_enc]
> [   75.148234]  v4l_qbuf+0x48/0x58
> [   75.148242]  __video_do_ioctl+0x200/0x37c
> [   75.148250]  video_usercopy+0x360/0x834
> [   75.148259]  video_ioctl2+0x38/0x48
> [   75.148267]  v4l2_ioctl+0x6c/0x80
> [   75.148276]  do_video_ioctl+0xefc/0x4b70
> [   75.148284]  v4l2_compat_ioctl32+0x5c/0xcc
> [   75.148294]  __arm64_compat_sys_ioctl+0xf4/0x240
> [   75.148304]  el0_svc_common+0xac/0x198
> [   75.148312]  el0_svc_compat_handler+0x2c/0x40
> [   75.148321]  el0_svc_compat+0x8/0x18
> [   75.148328] irq event stamp: 0
> [   75.148337] hardirqs last  enabled at (0): [<0000000000000000>]           (null)
> [   75.148347] hardirqs last disabled at (0): [<ffffff90080e65c0>] copy_process+0x380/0x115c
> [   75.148356] softirqs last  enabled at (0): [<ffffff90080e65d8>] copy_process+0x398/0x115c
> [   75.148364] softirqs last disabled at (0): [<0000000000000000>]           (null)
> [   75.148372] ---[ end trace 588bf529451e3531 ]---
> 
> Reported-by: Anand K Mistry <amistry@...omium.org>
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> ---
>   drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c | 8 ++++++++
>   drivers/media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c | 8 ++++++++
>   2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c b/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c
> index 97a1b6664c20..3bbd0bac56d6 100644
> --- a/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c
> +++ b/drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_drv.c
> @@ -242,6 +242,14 @@ static int mtk_vcodec_probe(struct platform_device *pdev)
>   		mtk_v4l2_err("[VPU] vpu device in not ready");
>   		return -EPROBE_DEFER;
>   	}
> +	if (!pdev->dev.dma_parms) {
> +		pdev->dev.dma_parms = devm_kzalloc(&pdev->dev,
> +						sizeof(*pdev->dev.dma_parms),
> +						GFP_KERNEL);
> +		if (!pdev->dev.dma_parms)
> +			return -ENOMEM;
> +	}

Since 9495b7e92f71, dma_parms is included in the platform_device itself 
and always set, so you can drop these allocation paths.

> +	dma_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32));

The segment size is simply a size, not a bitmask, so UINT_MAX would be 
more semantically appropriate.

Robin.

>   	vpu_wdt_reg_handler(dev->vpu_plat_dev, mtk_vcodec_dec_reset_handler,
>   			dev, VPU_RST_DEC);
> diff --git a/drivers/media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c b/drivers/media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c
> index 4d31f1ed113f..ff4a87485d69 100644
> --- a/drivers/media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c
> +++ b/drivers/media/platform/mtk-vcodec/mtk_vcodec_enc_drv.c
> @@ -249,6 +249,14 @@ static int mtk_vcodec_probe(struct platform_device *pdev)
>   		mtk_v4l2_err("[VPU] vpu device in not ready");
>   		return -EPROBE_DEFER;
>   	}
> +	if (!pdev->dev.dma_parms) {
> +		pdev->dev.dma_parms = devm_kzalloc(&pdev->dev,
> +						sizeof(*pdev->dev.dma_parms),
> +						GFP_KERNEL);
> +		if (!pdev->dev.dma_parms)
> +			return -ENOMEM;
> +	}
> +	dma_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32));
>   
>   	vpu_wdt_reg_handler(dev->vpu_plat_dev, mtk_vcodec_enc_reset_handler,
>   				dev, VPU_RST_ENC);
>