linux-kernel - Re: [PATCH 1/7] drm/tilcdc: don't use volatile with iowrite64

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Date:   Mon, 26 Jun 2017 11:54:25 +0300
From:   Jyri Sarha <jsarha@...com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        <linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
        <linux-ntb@...glegroups.com>, <linux-alpha@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>, <linux-crypto@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>
CC:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stephen Bates <sbates@...thlin.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH 1/7] drm/tilcdc: don't use volatile with iowrite64

On 06/22/17 19:48, Logan Gunthorpe wrote:
> This is a prep patch for adding a universal iowrite64.
> 
> The patch is to prevent compiler warnings when we add iowrite64 that
> would occur because there is an unnecessary volatile in this driver.
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Cc: Jyri Sarha <jsarha@...com>
> Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> Cc: David Airlie <airlied@...ux.ie>

Acked-by: Jyri Sarha <jsarha@...com>

> ---
>  drivers/gpu/drm/tilcdc/tilcdc_regs.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_regs.h b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> index 9d528c0a67a4..e9ce725698a9 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
> @@ -131,14 +131,14 @@ static inline void tilcdc_write(struct drm_device *dev, u32 reg, u32 data)
>  static inline void tilcdc_write64(struct drm_device *dev, u32 reg, u64 data)
>  {
>  	struct tilcdc_drm_private *priv = dev->dev_private;
> -	volatile void __iomem *addr = priv->mmio + reg;
> +	void __iomem *addr = priv->mmio + reg;
>  
>  #ifdef iowrite64
>  	iowrite64(data, addr);
>  #else
>  	__iowmb();
>  	/* This compiles to strd (=64-bit write) on ARM7 */
> -	*(volatile u64 __force *)addr = __cpu_to_le64(data);
> +	*(u64 __force *)addr = __cpu_to_le64(data);
>  #endif
>  }
>  
>