All of lore.kernel.org
 help / color / mirror / Atom feed
From: Eric Nelson <eric@nelint.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Eric Dumazet <edumazet@google.com>,
	Fugang Duan <fugang.duan@nxp.com>,
	Otavio Salvador <otavio@ossystems.com.br>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Troy Kisky <troy.kisky@boundarydevices.com>,
	rmk+kernel@arm.linux.org.uk, Simone <cjb.sw.nospam@gmail.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: Alignment issues with freescale FEC driver
Date: Fri, 23 Sep 2016 11:35:17 -0700	[thread overview]
Message-ID: <bc19d934-f50b-50d6-0f4f-ecfcb8a2a1c9@nelint.com> (raw)
In-Reply-To: <20160923181301.GD22965@lunn.ch>

Thanks Andrew.

On 09/23/2016 11:13 AM, Andrew Lunn wrote:
>> Since the hardware requires longword alignment for its' DMA transfers,
>> aligning the IP header will require a memcpy, right?
> 
> The vf610 FEC has an SHIFT16 bit in register ENETx_TACC, which inserts
> two padding bits on transmit. ENETx_RACC has the same.
> 
> What about your hardware?
> 

You got me with the RTFM!

>From the i.MX6DQ reference manual, bit 7 of ENET_RACC says this:

"RX FIFO Shift-16

When this field is set, the actual frame data starts at bit 16 of the first
word read from the RX FIFO aligning the Ethernet payload on a
32-bit boundary."

Same for the i.MX6UL.

I'm not sure what it will take to use this, but it seems to be exactly
what we're looking for.

WARNING: multiple messages have this Message-ID (diff)
From: eric@nelint.com (Eric Nelson)
To: linux-arm-kernel@lists.infradead.org
Subject: Alignment issues with freescale FEC driver
Date: Fri, 23 Sep 2016 11:35:17 -0700	[thread overview]
Message-ID: <bc19d934-f50b-50d6-0f4f-ecfcb8a2a1c9@nelint.com> (raw)
In-Reply-To: <20160923181301.GD22965@lunn.ch>

Thanks Andrew.

On 09/23/2016 11:13 AM, Andrew Lunn wrote:
>> Since the hardware requires longword alignment for its' DMA transfers,
>> aligning the IP header will require a memcpy, right?
> 
> The vf610 FEC has an SHIFT16 bit in register ENETx_TACC, which inserts
> two padding bits on transmit. ENETx_RACC has the same.
> 
> What about your hardware?
> 

You got me with the RTFM!

>From the i.MX6DQ reference manual, bit 7 of ENET_RACC says this:

"RX FIFO Shift-16

When this field is set, the actual frame data starts at bit 16 of the first
word read from the RX FIFO aligning the Ethernet payload on a
32-bit boundary."

Same for the i.MX6UL.

I'm not sure what it will take to use this, but it seems to be exactly
what we're looking for.

  parent reply	other threads:[~2016-09-23 18:35 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-23 16:43 Alignment issues with freescale FEC driver Eric Nelson
2016-09-23 16:43 ` Eric Nelson
2016-09-23 16:54 ` Eric Dumazet
2016-09-23 16:54   ` Eric Dumazet
2016-09-23 17:19   ` Eric Nelson
2016-09-23 17:19     ` Eric Nelson
2016-09-23 17:33     ` Eric Nelson
2016-09-23 17:33       ` Eric Nelson
2016-09-23 18:13       ` Andrew Lunn
2016-09-23 18:13         ` Andrew Lunn
2016-09-23 18:30         ` Russell King - ARM Linux
2016-09-23 18:30           ` Russell King - ARM Linux
2016-09-23 18:39           ` Eric Nelson
2016-09-23 18:39             ` Eric Nelson
2016-09-23 18:35         ` Eric Nelson [this message]
2016-09-23 18:35           ` Eric Nelson
2016-09-24  2:45           ` David Miller
2016-09-24  2:45             ` David Miller
2016-09-24  5:13             ` Andy Duan
2016-09-24  5:13               ` Andy Duan
2016-09-24 14:42               ` [PATCH 0/3] net: fec: updates to align IP header Eric Nelson
2016-09-24 14:42                 ` [PATCH 1/3] net: fec: remove QUIRK_HAS_RACC from i.mx25 Eric Nelson
2016-09-24 14:42                 ` [PATCH 2/3] net: fec: remove QUIRK_HAS_RACC from i.mx27 Eric Nelson
2016-09-24 14:42                 ` [PATCH 3/3] net: fec: align IP header in hardware Eric Nelson
2016-09-26  9:26                   ` David Laight
2016-09-26 18:39                     ` Eric Nelson
2016-09-28 16:42                       ` David Laight
2016-09-28 17:14                         ` Eric Nelson
2016-09-28 17:25                           ` Russell King - ARM Linux
2016-09-28 18:01                             ` Eric Nelson
2016-09-29 11:07                           ` David Laight
2016-09-30 13:27                             ` Eric Nelson
2016-09-30 13:49                               ` David Laight
2016-09-30 14:16                                 ` Eric Nelson
2016-10-01 19:52                                   ` Russell King - ARM Linux
2016-10-03 16:42                                     ` David Laight
2016-10-03 18:48                                     ` Eric Nelson
2016-10-08  2:44                               ` Andy Duan
2016-09-24 15:09                 ` [PATCH 0/3] net: fec: updates to align IP header Andy Duan
2016-09-24 15:29                   ` Eric Nelson
2016-09-27 11:40                 ` David Miller
2016-09-24  2:43       ` Alignment issues with freescale FEC driver David Miller
2016-09-24  2:43         ` David Miller
2016-09-24 12:27         ` Eric Nelson
2016-09-24 12:27           ` Eric Nelson
2016-09-23 17:37     ` Russell King - ARM Linux
2016-09-23 17:37       ` Russell King - ARM Linux
2016-09-23 18:26       ` Eric Nelson
2016-09-23 18:26         ` Eric Nelson
2016-09-23 18:37         ` Russell King - ARM Linux
2016-09-23 18:37           ` Russell King - ARM Linux
2016-09-23 18:49           ` Eric Nelson
2016-09-23 18:49             ` Eric Nelson
2016-09-23 20:22           ` Uwe Kleine-König
2016-09-23 20:22             ` Uwe Kleine-König

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bc19d934-f50b-50d6-0f4f-ecfcb8a2a1c9@nelint.com \
    --to=eric@nelint.com \
    --cc=andrew@lunn.ch \
    --cc=cjb.sw.nospam@gmail.com \
    --cc=edumazet@google.com \
    --cc=fugang.duan@nxp.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=netdev@vger.kernel.org \
    --cc=otavio@ossystems.com.br \
    --cc=rmk+kernel@arm.linux.org.uk \
    --cc=troy.kisky@boundarydevices.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.