From: David Miller <davem@davemloft.net>
To: niklas.cassel@axis.com
Cc: pavel@ucw.cz, peppe.cavallaro@st.com, alexandre.torgue@st.com,
Jose.Abreu@synopsys.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 2/4] net: stmmac: use correct barrier between coherent memory and MMIO
Date: Wed, 07 Mar 2018 10:32:26 -0500 (EST) [thread overview]
Message-ID: <20180307.103226.1538176953286317879.davem@davemloft.net> (raw)
In-Reply-To: <20180302232853.GA11108@axis.com>
From: Niklas Cassel <niklas.cassel@axis.com>
Date: Sat, 3 Mar 2018 00:28:53 +0100
> However, the last write we do is "DMA start transmission",
> this is a register in the IP, i.e. it is a write to the cache
> incoherent MMIO region (rather than a write to cache coherent memory).
> To ensure that all writes to cache coherent memory have
> completed before we start the DMA, we have to use the barrier
> wmb() (which performs a more extensive flush compared to
> dma_wmb()).
The is an implicit memory barrier between physical memory writes
and those to MMIO register space.
So as long as you place the dma_wmb() to ensure the correct
ordering within the descriptor words, you need nothing else
after the last descriptor word write.
next prev parent reply other threads:[~2018-03-07 15:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-26 21:47 [PATCH net-next 0/4] stmmac barrier fixes and cleanup Niklas Cassel
2018-02-26 21:47 ` [PATCH net-next 1/4] net: stmmac: ensure that the MSS desc is the last desc to set the own bit Niklas Cassel
2018-02-26 21:47 ` [PATCH net-next 2/4] net: stmmac: use correct barrier between coherent memory and MMIO Niklas Cassel
2018-03-02 9:20 ` Pavel Machek
2018-03-02 14:54 ` David Miller
2018-03-02 23:28 ` Niklas Cassel
2018-03-07 15:32 ` David Miller [this message]
2018-03-07 17:21 ` Niklas Cassel
2018-03-07 17:42 ` David Miller
2018-03-07 18:09 ` Niklas Cassel
2018-03-08 9:05 ` Pavel Machek
2018-02-26 21:47 ` [PATCH net-next 3/4] net: stmmac: ensure that the device has released ownership before reading data Niklas Cassel
2018-02-26 21:47 ` [PATCH net-next 4/4] net: stmmac: make dwmac4_release_tx_desc() clear all descriptor fields Niklas Cassel
2018-02-27 19:28 ` [PATCH net-next 0/4] stmmac barrier fixes and cleanup David Miller
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=20180307.103226.1538176953286317879.davem@davemloft.net \
--to=davem@davemloft.net \
--cc=Jose.Abreu@synopsys.com \
--cc=alexandre.torgue@st.com \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=niklas.cassel@axis.com \
--cc=pavel@ucw.cz \
--cc=peppe.cavallaro@st.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).