linux-kernel - Re: [PATCH v2] media: mtk-vpu: avoid unaligned access to DTCM buffer.

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Date:   Tue, 25 Feb 2020 13:34:42 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Hsin-Yi Wang <hsinyi@...omium.org>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Minghsiu Tsai <minghsiu.tsai@...iatek.com>,
        Houlong Wei <houlong.wei@...iatek.com>,
        Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        linux-media@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: mtk-vpu: avoid unaligned access to DTCM buffer.

On 2/14/20 1:01 PM, Hsin-Yi Wang wrote:
> struct vpu_run *run in vpu_init_ipi_handler() is an ioremapped DTCM (Data
> Tightly Coupled Memory) buffer shared with AP.  It's not able to do
> unaligned access. Otherwise kernel would crash due to unable to handle
> kernel paging request.
> 
> struct vpu_run {
> 	u32 signaled;
> 	char fw_ver[VPU_FW_VER_LEN];
> 	unsigned int	dec_capability;
> 	unsigned int	enc_capability;
> 	wait_queue_head_t wq;
> };
> 
> fw_ver starts at 4 byte boundary. If system enables
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, strscpy() will do
> read_word_at_a_time(), which tries to read 8-byte: *(unsigned long *)addr
> 
> Copy the string by memcpy_fromio() for this buffer to avoid unaligned
> access.
> 
> Fixes: 85709cbf1524 ("media: replace strncpy() by strscpy()")
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> ---
> Change in v2:
> - fix sparse warnings.

I still get sparse warnings:

drivers/media/platform/mtk-vpu/mtk_vpu.c:710:47:  warning: incorrect type in argument 1 (different address spaces)
drivers/media/platform/mtk-mdp/mtk_mdp_vpu.c:66:32:  warning: incorrect type in argument 3 (incompatible argument 1 (different address spaces))
drivers/media/platform/mtk-vcodec/vdec_vpu_if.c:111:22:  warning: incorrect type in assignment (incompatible argument 1 (different address spaces))
drivers/media/platform/mtk-vcodec/venc_vpu_if.c:96:54:  warning: incorrect type in argument 3 (incompatible argument 1 (different address spaces))

Regards,

	Hans

> ---
>  drivers/media/platform/mtk-vpu/mtk_vpu.c | 17 ++++++++++-------
>  drivers/media/platform/mtk-vpu/mtk_vpu.h |  2 +-
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/platform/mtk-vpu/mtk_vpu.c b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> index a768707abb94..c59373e84a33 100644
> --- a/drivers/media/platform/mtk-vpu/mtk_vpu.c
> +++ b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> @@ -600,15 +600,18 @@ int vpu_load_firmware(struct platform_device *pdev)
>  }
>  EXPORT_SYMBOL_GPL(vpu_load_firmware);
>  
> -static void vpu_init_ipi_handler(void *data, unsigned int len, void *priv)
> +static void vpu_init_ipi_handler(void __iomem *data, unsigned int len,
> +				 void *priv)
>  {
>  	struct mtk_vpu *vpu = (struct mtk_vpu *)priv;
> -	struct vpu_run *run = (struct vpu_run *)data;
> -
> -	vpu->run.signaled = run->signaled;
> -	strscpy(vpu->run.fw_ver, run->fw_ver, sizeof(vpu->run.fw_ver));
> -	vpu->run.dec_capability = run->dec_capability;
> -	vpu->run.enc_capability = run->enc_capability;
> +	struct vpu_run __iomem *run = data;
> +
> +	vpu->run.signaled = readl(&run->signaled);
> +	memcpy_fromio(vpu->run.fw_ver, run->fw_ver, sizeof(vpu->run.fw_ver));
> +	/* Make sure the string is NUL-terminated */
> +	vpu->run.fw_ver[sizeof(vpu->run.fw_ver) - 1] = '\0';
> +	vpu->run.dec_capability = readl(&run->dec_capability);
> +	vpu->run.enc_capability = readl(&run->enc_capability);
>  	wake_up_interruptible(&vpu->run.wq);
>  }
>  
> diff --git a/drivers/media/platform/mtk-vpu/mtk_vpu.h b/drivers/media/platform/mtk-vpu/mtk_vpu.h
> index d4453b4bcee9..a7ac351b19c1 100644
> --- a/drivers/media/platform/mtk-vpu/mtk_vpu.h
> +++ b/drivers/media/platform/mtk-vpu/mtk_vpu.h
> @@ -15,7 +15,7 @@
>   * VPU interfaces with other blocks by share memory and interrupt.
>   **/
>  
> -typedef void (*ipi_handler_t) (void *data,
> +typedef void (*ipi_handler_t) (void __iomem *data,
>  			       unsigned int len,
>  			       void *priv);
>  
>