linux-kernel - Re: [PATCH] fsldma: fsl_ioread64*() do not need lower_32

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Message-ID: <20200829150551.GA27225@roeck-us.net>
Date:   Sat, 29 Aug 2020 08:05:51 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <joerg.roedel@....com>,
        Li Yang <leoyang.li@....com>, Zhang Wei <zw@...kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vkoul@...nel.org>, linuxppc-dev@...ts.ozlabs.org,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fsldma: fsl_ioread64*() do not need lower_32_bits()

On Sat, Aug 29, 2020 at 02:45:38PM +0200, Luc Van Oostenryck wrote:
> For ppc32, the functions fsl_ioread64() & fsl_ioread64be()
> use lower_32_bits() as a fancy way to cast the pointer to u32
> in order to do non-atomic 64-bit IO.
> 
> But the pointer is already 32-bit, so simply cast the pointer to u32.
> 
> This fixes a compile error introduced by
>    ef91bb196b0d ("kernel.h: Silence sparse warning in lower_32_bits")
> 
> Fixes: ef91bb196b0db1013ef8705367bc2d7944ef696b

checkpatch complains about this and prefers 

Fixes: ef91bb196b0d ("kernel.h: Silence sparse warning in lower_32_bits")

Otherwise

Tested-by: Guenter Roeck <linux@...ck-us.net>

> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Cc: Li Yang <leoyang.li@....com>
> Cc: Zhang Wei <zw@...kernel.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Vinod Koul <vkoul@...nel.org>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: dmaengine@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@...il.com>
> ---
>  drivers/dma/fsldma.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/fsldma.h b/drivers/dma/fsldma.h
> index 56f18ae99233..6f6fa7641fa2 100644
> --- a/drivers/dma/fsldma.h
> +++ b/drivers/dma/fsldma.h
> @@ -205,7 +205,7 @@ struct fsldma_chan {
>  #else
>  static u64 fsl_ioread64(const u64 __iomem *addr)
>  {
> -	u32 fsl_addr = lower_32_bits(addr);
> +	u32 fsl_addr = (u32) addr;
>  	u64 fsl_addr_hi = (u64)in_le32((u32 *)(fsl_addr + 1)) << 32;
>  
>  	return fsl_addr_hi | in_le32((u32 *)fsl_addr);
> @@ -219,7 +219,7 @@ static void fsl_iowrite64(u64 val, u64 __iomem *addr)
>  
>  static u64 fsl_ioread64be(const u64 __iomem *addr)
>  {
> -	u32 fsl_addr = lower_32_bits(addr);
> +	u32 fsl_addr = (u32) addr;
>  	u64 fsl_addr_hi = (u64)in_be32((u32 *)fsl_addr) << 32;
>  
>  	return fsl_addr_hi | in_be32((u32 *)(fsl_addr + 1));
> -- 
> 2.28.0
>