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

From: Michal Simek
Date: Thu Sep 20 2018 - 02:24:16 EST


On 19.9.2018 20:08, Edgar E. Iglesias wrote:
> 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@xxxxxxxxxx>
>> ---
>>
>> 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.

Origin patch, which introduce this read with mask,
macfg = gem_readl(bp, DMACFG) & ~GEM_BF(RXBS, -1L);
was done in 2011 and from that time this function was extended a little
bit. I am even not quite sure if make sense to read this reg and apply
setting on the top of it.

Nicolas: Isn't it better simply compose that reg from scratch?

Thanks,
Michal