linux-kernel - Re: [PATCH 2/2] dmaengine: at_hdmac: Remove unused field values that do not fit

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Date:   Tue, 23 May 2023 15:04:14 +0100
From:   Tudor Ambarus <tudor.ambarus@...aro.org>
To:     Peter Rosin <peda@...ntia.se>, LKML <linux-kernel@...r.kernel.org>
Cc:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Vinod Koul <vkoul@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org
Subject: Re: [PATCH 2/2] dmaengine: at_hdmac: Remove unused field values that
 do not fit

Hi, Peter,

On 5/23/23 13:42, Peter Rosin wrote:
> The values are not used, and they do not fit in the intended
> register field (ATC_FC, 2 bits wide). Kill 'em all.
> 
Actually ATC_FC should be set to GENMASK(23, 21) and keep the other
definitions, see:
http://ww1.microchip.com/downloads/en/devicedoc/Atmel-6438-32-bit-ARM926-Embedded-Microprocessor-SAM9G45_Datasheet.pdf

After you update the patch you should also add:
Fixes: d8840a7edcf0 ("dmaengine: at_hdmac: Use bitfield access macros")
Cc: stable@...r.kernel.org
so that it gets backported to Linux-stable.

Feel free to add my R-b tag after addressing the comments:
Reviewed-by: Tudor Ambarus <tudor.ambarus@...aro.org>

> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  drivers/dma/at_hdmac.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index 6f352160bc3b..51d0a0c7aaf7 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -137,10 +137,6 @@
>  #define ATC_FC_MEM2PER		0x1		/* Mem-to-Periph (DMA) */
>  #define ATC_FC_PER2MEM		0x2		/* Periph-to-Mem (DMA) */
>  #define ATC_FC_PER2PER		0x3		/* Periph-to-Periph (DMA) */
> -#define ATC_FC_PER2MEM_PER	0x4		/* Periph-to-Mem (Peripheral) */
> -#define ATC_FC_MEM2PER_PER	0x5		/* Mem-to-Periph (Peripheral) */
> -#define ATC_FC_PER2PER_SRCPER	0x6		/* Periph-to-Periph (Src Peripheral) */
> -#define ATC_FC_PER2PER_DSTPER	0x7		/* Periph-to-Periph (Dst Peripheral) */
>  #define ATC_SRC_ADDR_MODE	GENMASK(25, 24)
>  #define ATC_SRC_ADDR_MODE_INCR	0x0		/* Incrementing Mode */
>  #define ATC_SRC_ADDR_MODE_DECR	0x1		/* Decrementing Mode */