linux-kernel - Re: [PATCH] drm: meson: fix address type confusion

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Date:   Wed, 8 Jan 2020 09:32:25 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Arnd Bergmann <arnd@...db.de>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kevin Hilman <khilman@...libre.com>
Cc:     Julien Masson <jmasson@...libre.com>,
        Maxime Jourdan <mjourdan@...libre.com>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: meson: fix address type confusion

On 07/01/2020 22:46, Arnd Bergmann wrote:
> Casting a pointer to dma_addr_t produces a warning:
> 
> drivers/gpu/drm/meson/meson_rdma.c: In function 'meson_rdma_free':
> drivers/gpu/drm/meson/meson_rdma.c:59:25: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>   priv->rdma.addr_phys = (dma_addr_t)NULL;
> 
> In this case, it's worse because the variable name has the suffix
> '_phys', which often indicates a phys_addr_t rather than dma_addr_t,
> i.e. yet another incompatible type.
> 
> Change it to use consistent naming and avoid NULL.
> 
> Fixes: 63fba242c464 ("drm/meson: add RDMA module driver")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/gpu/drm/meson/meson_drv.h  |  2 +-
>  drivers/gpu/drm/meson/meson_rdma.c | 12 ++++++------
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_drv.h b/drivers/gpu/drm/meson/meson_drv.h
> index f9a0c8e9d4d0..04fdf3826643 100644
> --- a/drivers/gpu/drm/meson/meson_drv.h
> +++ b/drivers/gpu/drm/meson/meson_drv.h
> @@ -135,7 +135,7 @@ struct meson_drm {
>  	} venc;
>  
>  	struct {
> -		dma_addr_t addr_phys;
> +		dma_addr_t addr_dma;
>  		uint32_t *addr;
>  		unsigned int offset;
>  	} rdma;
> diff --git a/drivers/gpu/drm/meson/meson_rdma.c b/drivers/gpu/drm/meson/meson_rdma.c
> index 25b34b1e72a7..130382178c63 100644
> --- a/drivers/gpu/drm/meson/meson_rdma.c
> +++ b/drivers/gpu/drm/meson/meson_rdma.c
> @@ -27,7 +27,7 @@ int meson_rdma_init(struct meson_drm *priv)
>  		/* Allocate a PAGE buffer */
>  		priv->rdma.addr =
>  			dma_alloc_coherent(priv->dev, SZ_4K,
> -					   &priv->rdma.addr_phys,
> +					   &priv->rdma.addr_dma,
>  					   GFP_KERNEL);
>  		if (!priv->rdma.addr)
>  			return -ENOMEM;
> @@ -47,16 +47,16 @@ int meson_rdma_init(struct meson_drm *priv)
>  
>  void meson_rdma_free(struct meson_drm *priv)
>  {
> -	if (!priv->rdma.addr && !priv->rdma.addr_phys)
> +	if (!priv->rdma.addr && !priv->rdma.addr_dma)
>  		return;
>  
>  	meson_rdma_stop(priv);
>  
>  	dma_free_coherent(priv->dev, SZ_4K,
> -			  priv->rdma.addr, priv->rdma.addr_phys);
> +			  priv->rdma.addr, priv->rdma.addr_dma);
>  
>  	priv->rdma.addr = NULL;
> -	priv->rdma.addr_phys = (dma_addr_t)NULL;
> +	priv->rdma.addr_dma = (dma_addr_t)0;
>  }
>  
>  void meson_rdma_setup(struct meson_drm *priv)
> @@ -118,11 +118,11 @@ void meson_rdma_flush(struct meson_drm *priv)
>  	meson_rdma_stop(priv);
>  
>  	/* Start of Channel 1 register writes buffer */
> -	writel(priv->rdma.addr_phys,
> +	writel(priv->rdma.addr_dma,
>  	       priv->io_base + _REG(RDMA_AHB_START_ADDR_1));
>  
>  	/* Last byte on Channel 1 register writes buffer */
> -	writel(priv->rdma.addr_phys + (priv->rdma.offset * RDMA_DESC_SIZE) - 1,
> +	writel(priv->rdma.addr_dma + (priv->rdma.offset * RDMA_DESC_SIZE) - 1,
>  	       priv->io_base + _REG(RDMA_AHB_END_ADDR_1));
>  
>  	/* Trigger Channel 1 on VSYNC event */
> 

Acked-by: Neil Armstrong <narmstrong@...libre.com>

Applying to drm-misc-fixes

Thanks,
Neil