linux-kernel - Re: Issues with i.MX SPI DMA transfers

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Date:   Wed, 3 Apr 2019 18:51:26 +0300
From:   Igor Plyatov <plyatov@...il.com>
To:     Robin Gong <yibin.gong@....com>
Cc:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        Fabio Estevam <festevam@...il.com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Andy Duan <fugang.duan@....com>, Han Xu <han.xu@....com>,
        Clark Wang <xiaoning.wang@....com>
Subject: Re: Issues with i.MX SPI DMA transfers

Dear Robin,

> Please apply the attached patch which is based on linux-next commit 
> 05d08e2995cbe6efdb993482ee0d38a77040861a.
> Please notice it has already contained two sdma patches revert - "ad0d92d7ba6a" and "25aaa75df1e6"

1) Yours source code is same as mine with exception of SDMA description 
for eCSPI in Device Tree.

I have changed Device Tree for i.MX6Q/DL as in attached patch and 
finally SPI interfaces operate more or less.

My patch revert back patches df07101e1c4a29e820df02f9989a066988b160e6 
and dd4b487b32a3571fdcc66062e661e3a3e360e35b. It is strange, because 
they are merged into mainline while ago. Maybe they are valid for some 
specific variant of i.MX SOC?

"More or less" means I have come to state described in first e-mail of 
this e-mail thread. Byte duplication (ERR009165) happens very often for 
eCSPI5 interface operating through DMA.

Test Conditions:
1.1. Interface under test is eCSPI1 or eCSPI5;
1.2. Four exemplars of "burn-neon" (CPU burn) executes in background to 
have 100% load for all 4 CPU cores (source code taken from 
https://raw.githubusercontent.com/ssvb/cpuburn-arm/dd5c5ba58d2b0b23cfab4a286f9d3f5510000f20/cpuburn-a8.S 
and https://hardwarebug.org/files/burn.S);
1.3. PC has running "ping -f embedded_device" to have network activity 
around 1 MiB/s Rx and Tx;
1.4. One exemplar of "spidev_test -D /dev/spidevX.0 -s FREQUENCY -b 8 -S 
512 -I 1000000 -l" executes at different frequencies;

Test Results for eCSPI1:
21 MHz    - success;
20 MHz    - success;
...
16 MHz    - success;
...
  8 MHz    - success;

Test Results for eCSPI5:
21 MHz    - failed;
20 MHz    - failed;
19 MHz    - failed;
...
12 MHz    - failed;
11 MHz    - failed;
10 MHz    - failed;
  9 MHz    - failed;
  8 MHz    - failed;
  7 MHz    - failed;
  6 MHz    - failed;
  5 MHz    - failed;
  4 MHz    - success.

Maybe it is worth to dump content of registers for eCSPI1 and eCSPI5 to 
compare them? I can do this if you will describe how to make it.

Maybe I'm wrong, but I suppose incorrect clock source for eCSPI5. Looks 
like it is worth to check correctness of driver "clk-imx6q.c" or 
something else responsible for eCSPI5 clock.

2) I want to improve description and replace magic numbers by constants 
in Device Tree for SDMA. I mean strings like "dmas = <&sdma 11 7 1>, 
<&sdma 12 7 2>;"?

So, finally Device Tree will have strings like

dmas = <&sdma SOME_DEF_A IMX_DMATYPE_.. DMA_PRIO_..>, <&sdma SOME_DEF_B 
IMX_DMATYPE_.. DMA_PRIO_..>;

I think, this will stop black magic manipulations for SDMA in Device 
Tree, by various developers.

Does first digit means "DMA request/event ID"? Where to find more info 
about this?

Does second digit means "enum sdma_peripheral_type"?

Does third digit means "enum imx_dma_prio"?

Where can I find description of difference between IMX_DMATYPE_CSPI (MCU 
domain CSPI) and IMX_DMATYPE_CSPI_SP (Shared CSPI)? Googling does not 
help too much.

Best wishes.
--
Igor Plyatov

View attachment "0001-Bugfix-for-incorrect-eCSPI-SDMA-numbers.patch" of type "text/x-patch" (2485 bytes)