linux-kernel - Re: [PATCH net-next 07/15] net: macb: simplify macb_adj_dma_desc

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Message-ID: <3a36ff13-893d-429f-b46e-ade24836d27a@lunn.ch>
Date: Fri, 17 Oct 2025 20:00:24 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Richard Cochran <richardcochran@...il.com>,
	Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Grégory Clement <gregory.clement@...tlin.com>,
	Benoît Monin <benoit.monin@...tlin.com>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>
Subject: Re: [PATCH net-next 07/15] net: macb: simplify
 macb_adj_dma_desc_idx()

On Tue, Oct 14, 2025 at 05:25:08PM +0200, Théo Lebrun wrote:
> The function body uses a switch statement on bp->hw_dma_cap and handles
> its four possible values: 0, is_64b, is_ptp, is_64b && is_ptp.
> 
> Instead, refactor by noticing that the return value is:
>    desc_size * MULT
> with MULT = 3 if is_64b && is_ptp,
>             2 if is_64b || is_ptp,
>             1 otherwise.
> 
> MULT can be expressed as:
>    1 + is_64b + is_ptp
> 
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> ---
>  drivers/net/ethernet/cadence/macb_main.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 7f74e280a3351ee7f961ff5ecd9550470b2e68eb..44a411662786ca4f309d6f9389b0d36819fc40ad 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -136,19 +136,13 @@ static unsigned int macb_dma_desc_get_size(struct macb *bp)
>  static unsigned int macb_adj_dma_desc_idx(struct macb *bp, unsigned int desc_idx)
>  {
>  #ifdef MACB_EXT_DESC
> -	switch (bp->hw_dma_cap) {
> -	case HW_DMA_CAP_64B:
> -	case HW_DMA_CAP_PTP:
> -		desc_idx <<= 1;
> -		break;
> -	case HW_DMA_CAP_64B_PTP:

I _think_ this makes HW_DMA_CAP_64B_PTP unused and it can be removed?

  Andrew