linux-kernel - Re: [PATCH] net: macb: Clean 64b dma addresses if they are not detected

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Date:   Wed, 19 Sep 2018 20:08:06 +0200
From:   "Edgar E. Iglesias" <edgar.iglesias@...inx.com>
To:     Michal Simek <michal.simek@...inx.com>
CC:     <linux-kernel@...r.kernel.org>, <monstr@...str.eu>,
        "Edgar E. Iglesias" <edgari@...inx.com>,
        "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <u-boot@...ts.denx.de>, Joe Hershberger <joe.hershberger@...com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>
Subject: Re: [PATCH] net: macb: Clean 64b dma addresses if they are not
 detected

On Wed, Sep 19, 2018 at 06:08:18PM +0200, Michal Simek wrote:
> Clear ADDR64 dma bit in DMACFG register in case that HW_DMA_CAP_64B
> is not detected on 64bit system.
> The issue was observed when bootloader(u-boot) does not check macb
> feature at DCFG6 register (DAW64_OFFSET) and enabling 64bit dma support
> by default. Then macb driver is reading DMACFG register back and only
> adding 64bit dma configuration but not cleaning it out.
> 
> This is also align with other features which are also cleared if they are not
> present.

Hi Michal,

> 
> Signed-off-by: Michal Simek <michal.simek@...inx.com>
> ---
> 
>  drivers/net/ethernet/cadence/macb_main.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 16e4ef7d7185..79707dff3f13 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -2163,6 +2163,8 @@ static void macb_configure_dma(struct macb *bp)
>  #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
>  		if (bp->hw_dma_cap & HW_DMA_CAP_64B)
>  			dmacfg |= GEM_BIT(ADDR64);
> +		else
> +			dmacfg &= ~GEM_BIT(ADDR64);
>  #endif

I think you might want to do this clearing outside of the #ifdef.
If CONFIG_ARCH_DMA_ADDR_T_64BIT is not defined, we'd want to make
sure the ADDR64 is cleared. E.g something like:

             dmacfg &= ~GEM_BIT(ADDR64);
#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
             if (bp->hw_dma_cap & HW_DMA_CAP_64B)
                     dmacfg |= GEM_BIT(ADDR64);
#endif


Same thing for the USE_HWSTAMP/PTP flags below.

Best regards,
Edgar


>  #ifdef CONFIG_MACB_USE_HWSTAMP
>  		if (bp->hw_dma_cap & HW_DMA_CAP_PTP)
> -- 
> 1.9.1
>