From: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>,
Michael Hennerich <Michael.Hennerich@analog.com>,
"linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Anatolij Gustschin <agust@denx.de>
Subject: Re: [PATCH 1/2] ads7846: Make buffers in ads7846_read12_ser and ads7845_read12_ser DMA save
Date: Wed, 04 May 2011 16:55:04 +0100 [thread overview]
Message-ID: <4DC176D8.70900@cam.ac.uk> (raw)
In-Reply-To: <4DC175A4.6060401@cam.ac.uk>
On 05/04/11 16:49, Jonathan Cameron wrote:
> On 05/04/11 16:22, Alexander Stein wrote:
>> req.sample needs its own cacheline otherwise accessing req.msg fetches
>> it in again.
>> Put req onto stack as it doesn't need to be DMA save.
>> req.sample is kzalloced itself for DMA access.
>> req.command doesn't need own cache line because it will only be written to
>> memory on dma_map_single. req.scratch is unsed at all.
>>
>> Note: This effect doesn't occur if the underlying SPI driver doesn't use
>> DMA at all.
>>
> How about using ____cacheline_aligned having moved 'sample' to the end of the
> structure?
>
> e.g.
>
> ...
> struct spi_transfer xfer[6];
> __be16 sample ____cacheline_aligned;
> }
hmm. I should probably have glanced further up the thread. Michael beat me to it
with the same suggestion!
next prev parent reply other threads:[~2011-05-04 15:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 14:02 ads7846: ads7846_read12_ser is not DMA save Alexander Stein
2011-05-04 14:17 ` Hennerich, Michael
2011-05-04 15:22 ` [PATCH 1/2] ads7846: Make buffers in ads7846_read12_ser and ads7845_read12_ser " Alexander Stein
2011-05-04 15:49 ` Jonathan Cameron
2011-05-04 15:55 ` Jonathan Cameron [this message]
2011-05-04 15:55 ` Alexander Stein
2011-05-04 16:07 ` Jonathan Cameron
2011-05-05 1:31 ` Dmitry Torokhov
2011-05-04 15:22 ` [PATCH 2/2] ads7846: Remove unused variable from struct ads7845_ser_req Alexander Stein
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