From: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> To: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org> Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Fabio Estevam <festevam-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: Re: possible MXS-i2c bug Date: Fri, 27 Apr 2012 18:37:56 +0200 [thread overview] Message-ID: <20120427163756.GH16504@pengutronix.de> (raw) In-Reply-To: <201204271753.39516.marex-ynQEQJNshbs@public.gmane.org> [-- Attachment #1: Type: text/plain, Size: 1517 bytes --] > But then you don't have the DMA chain linked. Which I wonder if the controller > has any problem with or not. I tried yesterday, got wrotes working perfectly, > but still had issues with reads, which is exactly what needs to be chained. Yes, the read needs chaining of two "DMA command blocks". That should be the only chain needed, because of how the driver handles reads. It is still one I2C message, though. > I'll poke further eventually. I really hope it works out! That would be great. > > Regarding Figure 27-10, the first I2C write command could be sent > > seperately (probably even via PIOQUEUE). > > I wonder if we want to combine pioqueue and DMA, that might create quite some > franken-driver. Might be true, yet I hope it won't. Most I2C transfers tend to be very small, so PIOQEUE would have some advantage here (less overhead). > > The only thing to be chained is the I2C read command and the actual > > reading of the data. > > > > Just checked, the FSL driver does it basically this way, too. > > Which doesn't mean FSL driver does it correctly, but it probably > worked for them and there was some bug in my DMA tinkering. It's only a proof-of-concept. We both know that :) (If it works, that is, AFAICT that one will fail for transfers bigger than PAGE_SIZE, too). Thanks, Wolfram -- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 198 bytes --]
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From: w.sang@pengutronix.de (Wolfram Sang) To: linux-arm-kernel@lists.infradead.org Subject: possible MXS-i2c bug Date: Fri, 27 Apr 2012 18:37:56 +0200 [thread overview] Message-ID: <20120427163756.GH16504@pengutronix.de> (raw) In-Reply-To: <201204271753.39516.marex@denx.de> > But then you don't have the DMA chain linked. Which I wonder if the controller > has any problem with or not. I tried yesterday, got wrotes working perfectly, > but still had issues with reads, which is exactly what needs to be chained. Yes, the read needs chaining of two "DMA command blocks". That should be the only chain needed, because of how the driver handles reads. It is still one I2C message, though. > I'll poke further eventually. I really hope it works out! That would be great. > > Regarding Figure 27-10, the first I2C write command could be sent > > seperately (probably even via PIOQUEUE). > > I wonder if we want to combine pioqueue and DMA, that might create quite some > franken-driver. Might be true, yet I hope it won't. Most I2C transfers tend to be very small, so PIOQEUE would have some advantage here (less overhead). > > The only thing to be chained is the I2C read command and the actual > > reading of the data. > > > > Just checked, the FSL driver does it basically this way, too. > > Which doesn't mean FSL driver does it correctly, but it probably > worked for them and there was some bug in my DMA tinkering. It's only a proof-of-concept. We both know that :) (If it works, that is, AFAICT that one will fail for transfers bigger than PAGE_SIZE, too). Thanks, Wolfram -- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 198 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20120427/10286e8f/attachment.sig>
next prev parent reply other threads:[~2012-04-27 16:37 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-04-26 11:26 possible MXS-i2c bug Marek Vasut 2012-04-26 11:41 ` Fabio Estevam [not found] ` <201204261326.29388.marex-ynQEQJNshbs@public.gmane.org> 2012-04-26 11:42 ` Wolfram Sang 2012-04-26 11:42 ` Wolfram Sang [not found] ` <20120426114201.GC3548-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2012-04-26 23:10 ` Marek Vasut 2012-04-26 23:10 ` Marek Vasut [not found] ` <201204270110.21377.marex-ynQEQJNshbs@public.gmane.org> 2012-04-27 14:59 ` Wolfram Sang 2012-04-27 14:59 ` Wolfram Sang [not found] ` <20120427145936.GD16504-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2012-04-27 15:08 ` Marek Vasut 2012-04-27 15:08 ` Marek Vasut [not found] ` <201204271708.53467.marex-ynQEQJNshbs@public.gmane.org> 2012-04-27 15:41 ` Wolfram Sang 2012-04-27 15:41 ` Wolfram Sang [not found] ` <20120427154119.GF16504-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2012-04-27 15:53 ` Marek Vasut 2012-04-27 15:53 ` Marek Vasut [not found] ` <201204271753.39516.marex-ynQEQJNshbs@public.gmane.org> 2012-04-27 16:37 ` Wolfram Sang [this message] 2012-04-27 16:37 ` Wolfram Sang [not found] ` <20120427163756.GH16504-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> 2012-04-28 3:03 ` [TEST PATCH] mxs-i2c DMA support Marek Vasut 2012-04-28 3:03 ` Marek Vasut
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