linux-kernel - Re: [PATCH v5 02/10] [media] marvell-ccic: fix DMA s/g desc number calculation

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Message-ID: <20190614094128.miryq2wfzoewjoyn@uno.localdomain>
Date:   Fri, 14 Jun 2019 11:41:28 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Lubomir Rintel <lkundrak@...sk>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jonathan Corbet <corbet@....net>, linux-media@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        James Cameron <quozl@...top.org>, Pavel Machek <pavel@....cz>,
        Libin Yang <lbyang@...vell.com>,
        Albert Wang <twang13@...vell.com>,
        Sakari Ailus <sakari.ailus@....fi>
Subject: Re: [PATCH v5 02/10] [media] marvell-ccic: fix DMA s/g desc number
 calculation

Hi Lubomir,

On Sun, May 05, 2019 at 04:00:23PM +0200, Lubomir Rintel wrote:
> The commit d790b7eda953 ("[media] vb2-dma-sg: move dma_(un)map_sg here")
> left dma_desc_nent unset. It previously contained the number of DMA
> descriptors as returned from dma_map_sg().
>
> We can now (since the commit referred to above) obtain the same value from
> the sg_table and drop dma_desc_nent altogether.
>
> Tested on OLPC XO-1.75 machine. Doesn't affect the OLPC XO-1's Cafe
> driver, since that one doesn't do DMA.
>
> Fixes: d790b7eda953df474f470169ebdf111c02fa7a2d

Could you use the proper 'fixes' format here?
Fixes: d790b7eda953 ("[media] vb2-dma-sg: move dma_(un)map_sg here")

> Signed-off-by: Lubomir Rintel <lkundrak@...sk>
> ---
>  drivers/media/platform/marvell-ccic/mcam-core.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/marvell-ccic/mcam-core.c b/drivers/media/platform/marvell-ccic/mcam-core.c
> index f1b301810260a..d97f39bde9bd6 100644
> --- a/drivers/media/platform/marvell-ccic/mcam-core.c
> +++ b/drivers/media/platform/marvell-ccic/mcam-core.c
> @@ -200,7 +200,6 @@ struct mcam_vb_buffer {
>  	struct list_head queue;
>  	struct mcam_dma_desc *dma_desc;	/* Descriptor virtual address */
>  	dma_addr_t dma_desc_pa;		/* Descriptor physical address */
> -	int dma_desc_nent;		/* Number of mapped descriptors */
>  };
>
>  static inline struct mcam_vb_buffer *vb_to_mvb(struct vb2_v4l2_buffer *vb)
> @@ -608,9 +607,11 @@ static void mcam_dma_contig_done(struct mcam_camera *cam, int frame)
>  static void mcam_sg_next_buffer(struct mcam_camera *cam)
>  {
>  	struct mcam_vb_buffer *buf;
> +	struct sg_table *sg_table;
>
>  	buf = list_first_entry(&cam->buffers, struct mcam_vb_buffer, queue);
>  	list_del_init(&buf->queue);
> +	sg_table = vb2_dma_sg_plane_desc(&buf->vb_buf.vb2_buf, 0);
>  	/*
>  	 * Very Bad Not Good Things happen if you don't clear
>  	 * C1_DESC_ENA before making any descriptor changes.
> @@ -618,7 +619,7 @@ static void mcam_sg_next_buffer(struct mcam_camera *cam)
>  	mcam_reg_clear_bit(cam, REG_CTRL1, C1_DESC_ENA);
>  	mcam_reg_write(cam, REG_DMA_DESC_Y, buf->dma_desc_pa);
>  	mcam_reg_write(cam, REG_DESC_LEN_Y,
> -			buf->dma_desc_nent*sizeof(struct mcam_dma_desc));
> +			sg_table->nents*sizeof(struct mcam_dma_desc));

Space betwen operators (it was there already, I know).

Apart for that, patch seems fine to me:
Reviewed-by: Jacopo Mondi <jacopo@...ndi.org>

Thanks
   j
>  	mcam_reg_write(cam, REG_DESC_LEN_U, 0);
>  	mcam_reg_write(cam, REG_DESC_LEN_V, 0);
>  	mcam_reg_set_bit(cam, REG_CTRL1, C1_DESC_ENA);
> --
> 2.21.0
>

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