linux-kernel - Re: [PATCH] net: marvell: fix MVNETA_TX_IN

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Date:   Fri, 6 Aug 2021 16:22:42 +0200
From:   Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To:     Maksim <bigunclemax@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: marvell: fix MVNETA_TX_IN_PRGRS bit number

Hello,

On Fri,  6 Aug 2021 17:04:37 +0300
Maksim <bigunclemax@...il.com> wrote:

> According to Armada XP datasheet bit at 0 position is corresponding for
> TxInProg indication.
> 
> Signed-off-by: Maksim <bigunclemax@...il.com>
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 76a7777c746da..de32e5b49053b 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -105,7 +105,7 @@
>  #define	MVNETA_VLAN_PRIO_TO_RXQ			 0x2440
>  #define      MVNETA_VLAN_PRIO_RXQ_MAP(prio, rxq) ((rxq) << ((prio) * 3))
>  #define MVNETA_PORT_STATUS                       0x2444
> -#define      MVNETA_TX_IN_PRGRS                  BIT(1)
> +#define      MVNETA_TX_IN_PRGRS                  BIT(0)
>  #define      MVNETA_TX_FIFO_EMPTY                BIT(8)
>  #define MVNETA_RX_MIN_FRAME_SIZE                 0x247c
>  /* Only exists on Armada XP and Armada 370 */

Indeed, I just checked the datasheet, and it's bit 0 in this register
that indicates if transmit is in progress. The only function using this
is mvneta_port_down(), which polls until MVNETA_TX_FIFO_EMPTY is set
and MVNETA_TX_IN_PRGRS is cleared in this register. Bit 1 in this
register is marked as reserved, read-only and read as zero, so I
suppose that mvneta_port_down() was basically never waiting for
MVNETA_TX_IN_PRGRS to clear.

Have you seen some actual visible issue, or was this just found by code
inspection ?

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com