Re: [PATCH stable 4.9] net: stmmac: Set dma ring length before enabling the DMA

[Lars Persson <lars.persson@axis.com>]

On 4/12/19 4:16 PM, Sasha Levin wrote:
> On Fri, Apr 12, 2019 at 01:17:05PM +0200, Lars Persson wrote:
>> This was fixed in upstream by commit 7d9e6c5afab6 ("net: stmmac: Integrate
>> XGMAC into main driver flow") that is a new feature commit.
>>
>> We found a race condition in the DMA init sequence that hits if the
>> PHY already has link up during stmmac_hw_setup. Since the ring length
>> was programmed after enabling the RX path, we might receive a packet
>> before the correct ring length is programmed. When that happened we
>> could not get reliable interrupts for DMA RX and the MTL complained
>> about RX FIFO overrun.
>>
>> The correct init sequence according to the data book for DWC Ethernet
>> QoS 4.10 is:
>> 1. Write Ring length
>> 2. Write Descriptor list base address
>> 3. Start the DMA.
>>
>> Signed-off-by: Lars Persson <larper@axis.com>
>> Cc: stable@vger.kernel.org # 4.9.x
>> Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
>> Cc: Alexandre Torgue <alexandre.torgue@st.com>
>> Cc: Jose Abreu <joabreu@synopsys.com>
> 
> What about 4.14? 7d9e6c5afab6 isn't in it either.
> 

I will send a separate patch for 4.14 in some days.

-Lars