Subject: Re: [PATCH] net: macb: fix endian code for avr32

From: Michal Simek <[email-masked]>
Date: Wed, 18 Mar 2015 15:40:50 +0100

Hi,

On 03/18/2015 11:57 AM, Ben Dooks wrote:
> [note this has yet to be compile tested on avr32]
> 
> The changes to run the macb driver in 29af05aeb98e ("net: macb:
> Add big endian CPU support") to support big endian operation on
> ARM may not work on AVR32 which already is naturally big endian
> architecture (and the driver already works here).
> 
> In this case  the readl/writel relaxed will do the opposite of __raw
> accesors which arleady work. Add an indirection of cdneth_ prefixed

here is type.

> accesors which are changed as necessary. Also do not issue the DMA
> descritpor endian fetch configuration for AVR32.

ditto.

> 
> From discussions with Arnd Bergman, the following fix changes the use
> of readl_relaxed and writel_relaxed with a version that can be put
> back to __raw_readl/__raw_writel for the CONFIG_AVR32 case (and also
> remove the change to the DMA descriptor endian).
> 
> Signed-off-by: Ben Dooks <[email-masked]>
> Reported-by: Arnd Bergmann <[email-masked]>
> --
> CC: Linux Networking List <[email-masked]>
> CC: Arun Chandran <[email-masked]>
> CC: Haavard Skinnemoen <[email-masked]>
> CC: Hans-Christian Egtvedt <[email-masked]>
> CC: Linux Kernel List <[email-masked]>
> CC: Nicolas Ferre <[email-masked]>
> ---
>  drivers/net/ethernet/cadence/macb.c | 14 +++++++-------
>  drivers/net/ethernet/cadence/macb.h | 20 ++++++++++++++------
>  2 files changed, 21 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> index b71e316..1c3f6e7 100644
> --- a/drivers/net/ethernet/cadence/macb.c
> +++ b/drivers/net/ethernet/cadence/macb.c
> @@ -449,7 +449,7 @@ static void macb_update_stats(struct macb *bp)
>  	WARN_ON((unsigned long)(end - p - 1) != (MACB_TPF - MACB_PFR) / 4);
>  
>  	for(; p < end; p++, reg++)
> -		*p += readl_relaxed(reg);
> +		*p += cdneth_readl(reg);
>  }
>  
>  static int macb_halt_tx(struct macb *bp)
> @@ -1587,7 +1587,7 @@ static void macb_configure_dma(struct macb *bp)
>  		dmacfg |= GEM_BIT(TXPBMS) | GEM_BF(RXBMS, -1L);
>  		dmacfg &= ~GEM_BIT(ENDIA_PKT);
>  		/* Tell the chip to byteswap descriptors on big-endian hosts */
> -#ifdef __BIG_ENDIAN
> +#if defined(__BIG_ENDIAN) && !defined(CONFIG_AVR32)
>  		dmacfg |= GEM_BIT(ENDIA_DESC);
>  #endif

the code has changed here - please rebase it on the top of net-next tree.

>  		if (bp->dev->features & NETIF_F_HW_CSUM)
> @@ -1836,14 +1836,14 @@ static void gem_update_stats(struct macb *bp)
>  
>  	for (i = 0; i < GEM_STATS_LEN; ++i, ++p) {
>  		u32 offset = gem_statistics[i].offset;
> -		u64 val = readl_relaxed(bp->regs + offset);
> +		u64 val = cdneth_readl(bp->regs + offset);
>  
>  		bp->ethtool_stats[i] += val;
>  		*p += val;
>  
>  		if (offset == GEM_OCTTXL || offset == GEM_OCTRXL) {
>  			/* Add GEM_OCTTXH, GEM_OCTRXH */
> -			val = readl_relaxed(bp->regs + offset + 4);
> +			val = cdneth_readl(bp->regs + offset + 4);
>  			bp->ethtool_stats[i] += ((u64)val) << 32;
>  			*(++p) += val;
>  		}
> @@ -2191,17 +2191,17 @@ static void macb_probe_queues(void __iomem *mem,
>  	unsigned int hw_q;
>  	u32 mid;
>  
> -	*queue_mask = 0x1;
> +	*queue_mask = 0x1;\
>  	*num_queues = 1;
>  
>  	/* is it macb or gem ? */
> -	mid = readl_relaxed(mem + MACB_MID);
> +	mid = cdneth_readl(mem + MACB_MID);
>  
>  	if (MACB_BFEXT(IDNUM, mid) != 0x2)
>  		return;
>  
>  	/* bit 0 is never set but queue 0 always exists */
> -	*queue_mask = readl_relaxed(mem + GEM_DCFG6) & 0xff;
> +	*queue_mask = cdneth_readl(mem + GEM_DCFG6) & 0xff;
>  
>  	*queue_mask |= 0x1;
>  
> diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> index 6cfff0b..c003e98 100644
> --- a/drivers/net/ethernet/cadence/macb.h
> +++ b/drivers/net/ethernet/cadence/macb.h
> @@ -422,19 +422,27 @@
>  		    << GEM_##name##_OFFSET))		\
>  	 | GEM_BF(name, value))
>  
> +#ifdef CONFIG_AVR32
> +#define cdneth_readl	__raw_readl
> +#define cdneth_writel	__raw_writel
> +#else
> +#define cdneth_readl	readl_relaxed
> +#define cdneth_writel	writel_relaxed
> +#endif

but this seems to me the way back. If cadence IP is big-endian then you can you what
I have suggested to you before. Just do endian detection on IP itself.
It means one checking will be for arm platforms if cpu runs big or little endian
and if IP is big on little endian.
It will end up in dynamic IO real/write functions which seems to the best way to go.
Of course doing this in this style means to add one more load in every io operations
but I don't think this is impact performance a lot.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform