From: Feng Tang <feng.tang@intel.com>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Serge Semin <fancer.lancer@gmail.com>,
Mark Brown <broonie@kernel.org>,
Grant Likely <grant.likely@secretlab.ca>,
Vinod Koul <vkoul@kernel.org>, Alan Cox <alan@linux.intel.com>,
Linus Walleij <linus.walleij@stericsson.com>,
Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>,
Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>,
Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Paul Burton <paulburton@kernel.org>,
Ralf Baechle <ralf@linux-mips.org>, Arnd Bergmann <arnd@arndb.de>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rob Herring <robh+dt@kernel.org>,
linux-mips@vger.kernel.org, devicetree@vger.kernel.org,
Jarkko Nikula <jarkko.nikula@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@intel.com>,
Linus Walleij <linus.walleij@linaro.org>,
Clement Leger <cleger@kalray.eu>,
linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 01/16] spi: dw: Add Tx/Rx finish wait methods to the MID DMA
Date: Thu, 21 May 2020 22:55:20 +0800 [thread overview]
Message-ID: <20200521145520.GB12568@shbuild999.sh.intel.com> (raw)
In-Reply-To: <20200521114736.b2azyfvym372vkdl@mobilestation>
Hi Serge,
On Thu, May 21, 2020 at 02:47:36PM +0300, Serge Semin wrote:
> Hello Feng,
>
> On Thu, May 21, 2020 at 11:09:24AM +0800, Feng Tang wrote:
> > Hi Serge,
> >
> > On Thu, May 21, 2020 at 04:21:51AM +0300, Serge Semin wrote:
>
> [nip]
>
> > > /*
> > > * dws->dma_chan_busy is set before the dma transfer starts, callback for rx
> > > * channel will clear a corresponding bit.
> > > @@ -200,6 +267,8 @@ static void dw_spi_dma_rx_done(void *arg)
> > > {
> > > struct dw_spi *dws = arg;
> > >
> > > + dw_spi_dma_wait_rx_done(dws);
> >
> > I can understand the problem about TX, but I don't see how RX
> > will get hurt, can you elaborate more? thanks
> >
> > - Feng
>
> Your question is correct. You are right with your hypothesis. Ideally upon the
> dw_spi_dma_rx_done() execution Rx FIFO must be already empty. That's why the
> commit log signifies the error being mostly related with Tx FIFO. But
> practically there are many reasons why Rx FIFO might be left with data:
> DMA engine failures, incorrect DMA configuration (if DW SPI or DW DMA driver
> messed something up), controller hanging up, and so on. It's better to catch
> an error at this stage while propagating it up to the SPI device drivers.
> Especially seeing the wait-check implementation doesn't gives us much of the
> execution overhead in normal conditions. So by calling dw_spi_dma_wait_rx_done()
> we make sure that all the data has been fetched and we may freely get the
> buffers back to the client driver.
I see your point about checking RX. But I still don't think checking
RX FIFO level is the right way to detect error. Some data left in
RX FIFO doesn't always mean a error, say for some case if there is
20 words in RX FIFO, and the driver starts a DMA request for 16
words, then after a sucessful DMA transaction, there are 4 words
left without any error.
Thanks,
Feng
>
> -Sergey
next prev parent reply other threads:[~2020-05-21 14:55 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-21 1:21 [PATCH v3 00/16] spi: dw: Add generic DW DMA controller support Serge Semin
2020-05-21 1:21 ` [PATCH v3 01/16] spi: dw: Add Tx/Rx finish wait methods to the MID DMA Serge Semin
2020-05-21 3:09 ` Feng Tang
2020-05-21 11:47 ` Serge Semin
2020-05-21 14:55 ` Feng Tang [this message]
2020-05-21 15:33 ` Serge Semin
2020-05-22 7:58 ` Feng Tang
2020-05-22 11:32 ` Serge Semin
2020-05-22 12:03 ` Feng Tang
2020-05-22 12:25 ` Serge Semin
2020-05-21 23:33 ` Serge Semin
2020-05-21 1:21 ` [PATCH v3 02/16] spi: dw: Enable interrupts in accordance with DMA xfer mode Serge Semin
2020-05-21 1:21 ` [PATCH v3 03/16] spi: dw: Discard static DW DMA slave structures Serge Semin
2020-05-21 9:57 ` Andy Shevchenko
[not found] ` <20200521121228.aqplh6eftylnys3p@mobilestation>
2020-05-21 12:49 ` Andy Shevchenko
2020-05-21 15:51 ` Mark Brown
2020-05-21 15:56 ` Andy Shevchenko
2020-05-21 15:58 ` Serge Semin
2020-05-21 16:02 ` Andy Shevchenko
2020-05-21 16:39 ` Mark Brown
2020-05-21 16:44 ` Andy Shevchenko
2020-05-21 17:29 ` Serge Semin
2020-05-21 1:21 ` [PATCH v3 06/16] spi: dw: Parameterize the DMA Rx/Tx burst length Serge Semin
2020-05-21 10:23 ` Andy Shevchenko
2020-05-21 1:21 ` [PATCH v3 07/16] spi: dw: Use DMA max burst to set the request thresholds Serge Semin
2020-05-21 10:49 ` Andy Shevchenko
2020-05-21 1:22 ` [PATCH v3 11/16] spi: dw: Remove DW DMA code dependency from DW_DMAC_PCI Serge Semin
2020-05-21 1:22 ` [PATCH v3 12/16] spi: dw: Add DW SPI DMA/PCI/MMIO dependency on the DW SPI core Serge Semin
2020-05-21 1:22 ` [PATCH v3 14/16] spi: dw: Add DMA support to the DW SPI MMIO driver Serge Semin
2020-05-21 1:22 ` [PATCH v3 16/16] dt-bindings: spi: Convert DW SPI binding to DT schema Serge Semin
[not found] ` <20200521012206.14472-10-Sergey.Semin@baikalelectronics.ru>
2020-05-21 10:47 ` [PATCH v3 09/16] spi: dw: Add core suffix to the DW APB SSI core source file Andy Shevchenko
2020-05-21 17:46 ` [PATCH v3 00/16] spi: dw: Add generic DW DMA controller support Andy Shevchenko
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=20200521145520.GB12568@shbuild999.sh.intel.com \
--to=feng.tang@intel.com \
--cc=Alexey.Malahov@baikalelectronics.ru \
--cc=Georgy.Vlasov@baikalelectronics.ru \
--cc=Ramil.Zaripov@baikalelectronics.ru \
--cc=Sergey.Semin@baikalelectronics.ru \
--cc=alan@linux.intel.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=arnd@arndb.de \
--cc=broonie@kernel.org \
--cc=cleger@kalray.eu \
--cc=devicetree@vger.kernel.org \
--cc=fancer.lancer@gmail.com \
--cc=grant.likely@secretlab.ca \
--cc=jarkko.nikula@linux.intel.com \
--cc=linus.walleij@linaro.org \
--cc=linus.walleij@stericsson.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-spi@vger.kernel.org \
--cc=paulburton@kernel.org \
--cc=ralf@linux-mips.org \
--cc=robh+dt@kernel.org \
--cc=tglx@linutronix.de \
--cc=tsbogend@alpha.franken.de \
--cc=vkoul@kernel.org \
--cc=wan.ahmad.zainie.wan.mohamad@intel.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).