netdev - Re: [PATCH 1/1] net: axienet: Move reset before DMA detection

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Date: Wed, 21 Jun 2023 16:10:06 +0300
From: Maxim Kochetkov <fido_max@...ox.ru>
To: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>,
 "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, "Simek, Michal" <michal.simek@....com>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] net: axienet: Move reset before DMA detection

On 21.06.2023 15:23, Pandey, Radhey Shyam wrote:
>> -----Original Message-----
>> From: Maxim Kochetkov <fido_max@...ox.ru>
>> Sent: Wednesday, June 21, 2023 4:57 PM
>> To: netdev@...r.kernel.org
>> Cc: Maxim Kochetkov <fido_max@...ox.ru>; Pandey, Radhey Shyam
>> <radhey.shyam.pandey@....com>; David S. Miller
>> <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Jakub
>> Kicinski <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; Simek,
>> Michal <michal.simek@....com>; linux-arm-kernel@...ts.infradead.org;
>> linux-kernel@...r.kernel.org
>> Subject: [PATCH 1/1] net: axienet: Move reset before DMA detection
>>
>> DMA detection will fail if axinet was started before (by boot loader, boot
>> ROM, etc). In this state axinet will not start properly.
>> So move axinet reset before DMA detection.
> 
> Please provide more detail on the failing testcase. In which scenario we are
> seeing DMA detection failure? What is error log . Is it random?
> 

XAXIDMA_TX_CDESC_OFFSET + 4 register (MM2S_CURDESC_MSB) is used to 
detect 64 DMA capability here. But datasheet says: When DMACR.RS is 1 
(axinet is in enabled state), CURDESC_PTR becomes Read Only (RO) and is 
used to fetch the first
descriptor. So iowrite32()/ioread32() trick to this register is failed.