linux-kernel - Re: [PATCH 1/2] dmaengine: at_hdmac: Repair bitfield macros for peripheral ID handling

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Message-ID: <4b5feef2-8d6f-20b1-9763-6e9552c4eb1c@linaro.org>
Date:   Tue, 23 May 2023 16:15:52 +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 1/2] dmaengine: at_hdmac: Repair bitfield macros for
 peripheral ID handling



On 5/23/23 13:42, Peter Rosin wrote:
> The MSB part of the peripheral IDs need to go into the ATC_SRC_PER_MSB
> and ATC_DST_PER_MSB fields. Not the LSB part.
> 
> This fixes a severe regression for TSE-850 devices (compatible
> axentia,tse850v3) where output to the audio I2S codec (the main
> purpose of the device) simply do not work.
> 

Indeed, sorry Peter.

> While at it, rewrite the macros as inline functions to evade checkpatch
> warnings about argument reuse.
> 
> Fixes: d8840a7edcf0 ("dmaengine: at_hdmac: Use bitfield access macros")

cc stable please

> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  drivers/dma/at_hdmac.c | 35 ++++++++++++++++++++++++++++-------
>  1 file changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index 8858470246e1..6f352160bc3b 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -153,8 +153,6 @@
>  #define ATC_AUTO		BIT(31)		/* Auto multiple buffer tx enable */
>  
>  /* Bitfields in CFG */
> -#define ATC_PER_MSB(h)	((0x30U & (h)) >> 4)	/* Extract most significant bits of a handshaking identifier */
> -
>  #define ATC_SRC_PER		GENMASK(3, 0)	/* Channel src rq associated with periph handshaking ifc h */
>  #define ATC_DST_PER		GENMASK(7, 4)	/* Channel dst rq associated with periph handshaking ifc h */
>  #define ATC_SRC_REP		BIT(8)		/* Source Replay Mod */
> @@ -181,10 +179,7 @@
>  #define ATC_DPIP_HOLE		GENMASK(15, 0)
>  #define ATC_DPIP_BOUNDARY	GENMASK(25, 16)
>  
> -#define ATC_SRC_PER_ID(id)	(FIELD_PREP(ATC_SRC_PER_MSB, (id)) |	\
> -				 FIELD_PREP(ATC_SRC_PER, (id)))
> -#define ATC_DST_PER_ID(id)	(FIELD_PREP(ATC_DST_PER_MSB, (id)) |	\
> -				 FIELD_PREP(ATC_DST_PER, (id)))
> +#define ATC_PER_MSB		GENMASK(5, 4)	/* Extract MSBs of a handshaking identifier */
>  
>  
>  
> @@ -1780,6 +1775,32 @@ static bool at_dma_filter(struct dma_chan *chan, void *slave)
>  	}
>  }
>  
> +/**
> + * atc_src_per_id - prepare the source peripheral fields of the CFG
> + * register for the given peripheral handshaking id.
> + *
> + * @per_id: the peripheral id
> + */
> +static inline u32 atc_src_per_id(unsigned int per_id)
> +{
> +	return FIELD_PREP(ATC_SRC_PER_MSB,
> +			  FIELD_GET(ATC_PER_MSB, per_id)) |
> +		FIELD_PREP(ATC_SRC_PER, per_id);
> +}

I still prefer a macro, would you use the following instead?
+#define ATC_SRC_PER_ID(id)                                            \
+       ({ typeof(id) _id = (id);                                      \
+          FIELD_PREP(ATC_SRC_PER_MSB, FIELD_GET(ATC_PER_MSB, _id)) |  \
+          FIELD_PREP(ATC_SRC_PER, _id); })

Cheers,
ta