From: Peng Ma <peng.ma@nxp.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Peter Chen <peter.chen@nxp.com>, Peng Fan <peng.fan@nxp.com>,
Jacky Bai <ping.bai@nxp.com>, Leo Zhang <leo.zhang@nxp.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Mirela Rabulea <mirela.rabulea@nxp.com>,
"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
Mircea Pop <mircea.pop@nxp.com>, Fancy Fang <chen.fang@nxp.com>,
Leonard Crestez <leonard.crestez@nxp.com>,
"festevam@gmail.com" <festevam@gmail.com>,
Robin Gong <yibin.gong@nxp.com>, Abel Vesa <abel.vesa@nxp.com>,
Anson Huang <anson.huang@nxp.com>,
BOUGH CHEN <haibo.chen@nxp.com>, Ying Liu <victor.liu@nxp.com>,
Shenwei Wang <shenwei.wang@nxp.com>,
Clark Wang <xiaoning.wang@nxp.com>,
Viorel Suman <viorel.suman@nxp.com>,
Robert Chiras <robert.chiras@nxp.com>,
Iuliana Prodan <iuliana.prodan@nxp.com>,
"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
Zening Wang <zening.wang@nxp.com>, Han Xu <han.xu@nxp.com>,
Daniel Baluta <daniel.baluta@nxp.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Aisheng Dong <aisheng.dong@nxp.com>,
Horia Geanta <horia.geanta@nxp.com>,
Joakim Zhang <qiangqing.zhang@nxp.com>,
"linux@rempel-privat.de" <linux@rempel-privat.de>,
Ranjani Vaidyanathan <ranjani.vaidyanathan@nxp.com>,
Bogdan Florin Vlad <bogdan.vlad@nxp.com>,
"kernel@pengutronix.de" <kernel@pengutronix.de>,
"shawnguo@kernel.org" <shawnguo@kernel.org>,
Jun Li <jun.li@nxp.com>
Subject: RE: [EXT] Re: [PATCH] i2c: imx: Defer probing if EDMA not available
Date: Fri, 13 Dec 2019 10:33:51 +0000 [thread overview]
Message-ID: <VI1PR04MB44318D7C92B6A29D04840B0DED540@VI1PR04MB4431.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20191212105857.GE25745@shell.armlinux.org.uk>
>-----Original Message-----
>From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
>Sent: 2019年12月12日 18:59
>To: Peng Ma <peng.ma@nxp.com>
>Cc: shawnguo@kernel.org; s.hauer@pengutronix.de;
>linux-kernel@vger.kernel.org; linux@rempel-privat.de; Abel Vesa
><abel.vesa@nxp.com>; Aisheng Dong <aisheng.dong@nxp.com>; Anson Huang
><anson.huang@nxp.com>; Bogdan Florin Vlad <bogdan.vlad@nxp.com>;
>BOUGH CHEN <haibo.chen@nxp.com>; Clark Wang
><xiaoning.wang@nxp.com>; Daniel Baluta <daniel.baluta@nxp.com>; Fancy
>Fang <chen.fang@nxp.com>; Han Xu <han.xu@nxp.com>; Horia Geanta
><horia.geanta@nxp.com>; Iuliana Prodan <iuliana.prodan@nxp.com>; Jacky
>Bai <ping.bai@nxp.com>; Joakim Zhang <qiangqing.zhang@nxp.com>; Jun Li
><jun.li@nxp.com>; Leo Zhang <leo.zhang@nxp.com>; Leonard Crestez
><leonard.crestez@nxp.com>; Mircea Pop <mircea.pop@nxp.com>; Mirela
>Rabulea <mirela.rabulea@nxp.com>; Peng Fan <peng.fan@nxp.com>; Peter
>Chen <peter.chen@nxp.com>; Ranjani Vaidyanathan
><ranjani.vaidyanathan@nxp.com>; Robert Chiras <robert.chiras@nxp.com>;
>Robin Gong <yibin.gong@nxp.com>; Shenwei Wang
><shenwei.wang@nxp.com>; Viorel Suman <viorel.suman@nxp.com>; Ying Liu
><victor.liu@nxp.com>; Zening Wang <zening.wang@nxp.com>;
>kernel@pengutronix.de; festevam@gmail.com;
>linux-arm-kernel@lists.infradead.org; linux-i2c@vger.kernel.org
>Subject: Re: [EXT] Re: [PATCH] i2c: imx: Defer probing if EDMA not available
>
>Caution: EXT Email
>
>On Thu, Dec 12, 2019 at 03:09:32AM +0000, Peng Ma wrote:
>> Hello Russell,
>>
>> Thanks very much for your strict guidance and comments.
>> I realized it is hard to us that we want to i2c used edma when edma
>> probe after i2c probe.
>
>I have no problem with that aim. I'm just very concerned by the proposed
>implementation, especially when it has already been proven to cause
>regressions in the kernel. I seem to remember that the infinite loop caused
>other issues, such as the system being unable to complete booting.
>
>> I look forward to discussing with you as below, if you like.
>> Thanks.
>>
>> You say I could do this:
>> "So, if you want to do this (and yes, I'd also encourage it to be
>> conditional on EDMA being built-in, as I2C is commonly used as a way
>> to get at RTCs, which are read before kernel modules can be loaded)
>> then you MUST move
>> i2c_imx_dma_request() before
>> i2c_add_numbered_adapter() to avoid the infinite loop."
>>
>> Even if I do this, It's hard to avoid the infinite loop of i2c probe caused by
>EDMA(build-in) initialization failure.
>
>It isn't clear what you mean here.
>
>If EDMA fails to probe (because fsl_edma_probe() returns an error other than
>EPROBE_DEFER) then of_dma_find_controller() will return NULL. That will be
>propagated down through i2c_imx_dma_request(). This is no different from the
>case where EDMA is built as a module. It is also no different from the case
>where EDMA hasn't yet been probed.
>
Hello Russell,
The result of my test is not like that, It is still with probe loop, the test config as follows:
1.EDMA build-in
2.return -EINVAL top of fsl_edma_probe when edma probe
3.i2c probe with original patch, I put the i2c_imx_dma_request in front of i2c_add_numbered_adapter or used original patch.
I send you the function of_dma_request_slave_channel could explain it last mail,
"Return -EPROBE_DEFER" depends on:
1. edma not probe or probe failed
2. There is edma node in DTS and I2C with edma property
>If i2c_imx_dma_request() is placed after i2c_add_numbered_adapter(), and
>EPROBE_DEFER is propagated out of i2c_imx_probe(), then _yes_, it will cause
>an infinite loop, because you are replicating the exact conditions that caused
>the attempt to propagate i2c_imx_dma_request()'s return value to be reverted
>last time - which brought the kernel to a grinding halt.
>
>If i2c_imx_dma_request() is placed before i2c_add_numbered_adapter(), then
>there is no infinite deferred probing loop - yes, i2c_imx_probe() will be called as
>a result of other drivers successfully probing, and each time it will return
>EPROBE_DEFER, but the _key_ point is that the action of i2c_imx_probe() will
>not _self trigger_ the deferred probing _and_ place itself onto the deferred
>probe list.
>
>Please, rather than continuing to send emails arguing over this point,
>investigate the stated issue with some practical tests:
>
>1. Make i2c_imx_probe() propagate i2c_imx_dma_request()'s return value,
> as it did in the original patch.
>2. Build i2c-imx into the kernel.
>3. Build edma as a module.
>4. Build and test boot the kernel and check what happens.
>5. Move i2c_imx_dma_request() before i2c_add_numbered_adapter() 6. Build
>and test boot the resulting kernel and note any differences.
>
[Peng Ma] the i2c probe loop still exist but not infinite loop with below cases:
1:
Used original patch
Build i2c-imx into the kernel
Build edma into the kernel
2:
Used original patch
Build i2c-imx into the kernel
Build edma into the kernel
Move i2c_imx_dma_request() before i2c_add_numbered_adapter()
3:
Used original patch
Build i2c-imx into the kernel
Build edma as a module
Move i2c_imx_dma_request() before i2c_add_numbered_adapter()
I saw the commit e8c220fac415d9f4a994b0c2871b835feac1eb4e you said
1. i2c_imx_probe() is called and successfully registers an I2C
adapter via i2c_add_numbered_adapter()
2. As a part of i2c_add_numbered_adapter() new I2C slave devices
are added from DT which results in a call to
driver_deferred_probe_trigger()
3. i2c_imx_probe() continues and calls i2c_imx_dma_request() which
due to lack of proper DMA driver returns -EPROBE_DEFER
4. i2c_imx_probe() fails, removes I2C adapter and returns
-EPROBE_DEFER, which places it into deferred probe list
5. Deferred probe work triggered in #2 above kicks in and calls
i2c_imx_probe() again thus bringing us to step #1"
Can I understand 4, you mean just remove I2C adapter the i2c slave devices not be removed? Then the i2c slave devices will probe their drivers triggered the driver_deferred_probe_trigger().
If so, My test is not like this, when the i2c probe failed the i2c slave devices will be removed and I2C adapter will be removed too.
Best Regards,
Peng
>--
>RMK's Patch system:
>https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ar
>mlinux.org.uk%2Fdeveloper%2Fpatches%2F&data=02%7C01%7Cpeng.ma
>%40nxp.com%7Ca535712eabe343a51c2f08d77ef250e4%7C686ea1d3bc2b4c6
>fa92cd99c5c301635%7C0%7C0%7C637117451627341155&sdata=%2Fyz
>xAI8%2FezVRwGTaT4vYa3CMkIMsaSYiaH8DjvJWUKA%3D&reserved=0
>FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps
>up According to speedtest.net: 11.9Mbps down 500kbps up
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-12-13 10:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 7:12 [PATCH] i2c: imx: Defer probing if EDMA not available Peng Ma
2019-11-27 7:27 ` Uwe Kleine-König
2019-11-28 2:45 ` [EXT] " Peng Ma
2019-11-28 10:06 ` Russell King - ARM Linux admin
2019-12-11 10:25 ` [EXT] " Peng Ma
2019-12-11 10:43 ` Russell King - ARM Linux admin
2019-12-11 11:22 ` Peng Ma
2019-12-11 11:42 ` Russell King - ARM Linux admin
2019-12-12 3:09 ` Peng Ma
2019-12-12 10:58 ` Russell King - ARM Linux admin
2019-12-13 10:33 ` Peng Ma [this message]
2019-12-13 10:50 ` Russell King - ARM Linux admin
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=VI1PR04MB44318D7C92B6A29D04840B0DED540@VI1PR04MB4431.eurprd04.prod.outlook.com \
--to=peng.ma@nxp.com \
--cc=abel.vesa@nxp.com \
--cc=aisheng.dong@nxp.com \
--cc=anson.huang@nxp.com \
--cc=bogdan.vlad@nxp.com \
--cc=chen.fang@nxp.com \
--cc=daniel.baluta@nxp.com \
--cc=festevam@gmail.com \
--cc=haibo.chen@nxp.com \
--cc=han.xu@nxp.com \
--cc=horia.geanta@nxp.com \
--cc=iuliana.prodan@nxp.com \
--cc=jun.li@nxp.com \
--cc=kernel@pengutronix.de \
--cc=leo.zhang@nxp.com \
--cc=leonard.crestez@nxp.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=linux@rempel-privat.de \
--cc=mircea.pop@nxp.com \
--cc=mirela.rabulea@nxp.com \
--cc=peng.fan@nxp.com \
--cc=peter.chen@nxp.com \
--cc=ping.bai@nxp.com \
--cc=qiangqing.zhang@nxp.com \
--cc=ranjani.vaidyanathan@nxp.com \
--cc=robert.chiras@nxp.com \
--cc=s.hauer@pengutronix.de \
--cc=shawnguo@kernel.org \
--cc=shenwei.wang@nxp.com \
--cc=victor.liu@nxp.com \
--cc=viorel.suman@nxp.com \
--cc=xiaoning.wang@nxp.com \
--cc=yibin.gong@nxp.com \
--cc=zening.wang@nxp.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).