Messages in this thread | | | From | "Oskar Schirmer" <> | Date | Tue, 11 May 2010 16:12:11 +0200 | Subject | Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines |
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On Mon, May 10, 2010 at 23:05:47 -0700, Dmitry Torokhov wrote: > OK, then I have the following which I will apply unless someone shouts.
Looks good, we tested it on G45, works fine.
Oskar
> -- > Dmitry > > Input: ad7877 - keep dma rx buffers in seperate cache lines > > From: Oskar Schirmer <os@emlix.com> > > With dma based spi transmission, data corruption is observed > occasionally. With dma buffers located right next to msg and > xfer fields, cache lines correctly flushed in preparation for > dma usage may be polluted again when writing to fields in the > same cache line. > > Make sure cache fields used with dma do not share cache lines > with fields changed during dma handling. As both fields are part > of a struct that is allocated via kzalloc, thus cache aligned, > moving the fields to the 1st position and insert padding for > alignment does the job. > > Signed-off-by: Oskar Schirmer <os@emlix.com> > Signed-off-by: Daniel Glöckner <dg@emlix.com> > Signed-off-by: Oliver Schneidewind <osw@emlix.com> > Signed-off-by: Johannes Weiner <jw@emlix.com> > Acked-by: Mike Frysinger <vapier@gentoo.org> > [dtor@mail.ru - changed to use ___cacheline_aligned at suggestion > of akpm] > Signed-off-by: Dmitry Torokhov <dtor@mail.ru> > --- > > drivers/input/touchscreen/ad7877.c | 15 ++++++++++++--- > 1 files changed, 12 insertions(+), 3 deletions(-) > > > diff --git a/drivers/input/touchscreen/ad7877.c b/drivers/input/touchscreen/ad7877.c > index e019d53..0d2d7e5 100644 > --- a/drivers/input/touchscreen/ad7877.c > +++ b/drivers/input/touchscreen/ad7877.c > @@ -156,9 +156,14 @@ struct ser_req { > u16 reset; > u16 ref_on; > u16 command; > - u16 sample; > struct spi_message msg; > struct spi_transfer xfer[6]; > + > + /* > + * DMA (thus cache coherency maintenance) requires the > + * transfer buffers to live in their own cache lines. > + */ > + u16 sample ____cacheline_aligned; > }; > > struct ad7877 { > @@ -182,8 +187,6 @@ struct ad7877 { > u8 averaging; > u8 pen_down_acc_interval; > > - u16 conversion_data[AD7877_NR_SENSE]; > - > struct spi_transfer xfer[AD7877_NR_SENSE + 2]; > struct spi_message msg; > > @@ -195,6 +198,12 @@ struct ad7877 { > spinlock_t lock; > struct timer_list timer; /* P: lock */ > unsigned pending:1; /* P: lock */ > + > + /* > + * DMA (thus cache coherency maintenance) requires the > + * transfer buffers to live in their own cache lines. > + */ > + u16 conversion_data[AD7877_NR_SENSE] ____cacheline_aligned; > }; > > static int gpio3; > >
-- oskar schirmer, emlix gmbh, http://www.emlix.com fon +49 551 30664-0, fax -11, bahnhofsallee 1b, 37081 göttingen, germany sitz der gesellschaft: göttingen, amtsgericht göttingen hr b 3160 geschäftsführer: dr. uwe kracke, ust-idnr.: de 205 198 055
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