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From: kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org
To: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	linux-spi <linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"Noralf Trønnes" <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>,
	linux-rpi-kernel
	<linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>,
	meghana.madhyastha-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Subject: Re: [PATCH v4 2/4] spi: Split spi message into max_dma_len size chunks
Date: Fri, 12 Apr 2019 12:03:35 +0200	[thread overview]
Message-ID: <B40B4313-3965-42D9-9228-92E275A7D2AA@martin.sperl.org> (raw)
In-Reply-To: <20190412094721.GE6909-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>


> On 12.04.2019, at 11:47, Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:
> 
> 
>> In a previous version of this I suggested to Meghana to put this in the
>> driver, but Mark wanted it in the core.
> 
> If we want to do this at a lower level the DMA code could hide this
> limitation from the upper layers; presumably the SPI driver isn't the
> only thing that might run into this.

For clarification:
There is a register of the SPI controller where you have to configure the
number of bytes that it will request via DMA (primarily support transfers
that are not a multiple of 4 - the data is transferred by DMA as words).
So it is not really related to the general DMA implementation but to the
DMA (request) support of the SPI controller.

Martin

  parent reply	other threads:[~2019-04-12 10:03 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-11 16:42 [PATCH v4 0/4] Chunk splitting of spi transfers Noralf Trønnes
2019-04-11 16:42 ` [PATCH v4 1/4] spi: Remove warning in spi_split_transfers_maxsize() Noralf Trønnes
     [not found] ` <20190411164235.49771-1-noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
2019-04-11 16:42   ` [PATCH v4 2/4] spi: Split spi message into max_dma_len size chunks Noralf Trønnes
2019-04-11 18:18     ` Lukas Wunner
2019-04-11 21:02       ` Noralf Trønnes
2019-04-12  9:47         ` Mark Brown
     [not found]           ` <20190412094721.GE6909-GFdadSzt00ze9xe1eoZjHA@public.gmane.org>
2019-04-12 10:03             ` kernel-TqfNSX0MhmxHKSADF0wUEw [this message]
2019-04-12 10:22               ` Mark Brown
2019-04-12 10:54           ` Lukas Wunner
2019-04-12 11:09             ` Mark Brown
2019-04-12 11:16               ` Lukas Wunner
2019-04-12 11:28                 ` Mark Brown
     [not found]                 ` <20190412111615.25iogtr6qwc5zbx7-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
2019-04-12 11:34                   ` kernel-TqfNSX0MhmxHKSADF0wUEw
2019-04-12 10:46         ` Lukas Wunner
2019-04-12 11:46           ` Mark Brown
2019-04-11 20:39     ` Noralf Trønnes
     [not found]     ` <20190411164235.49771-3-noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
2019-04-12  9:08       ` Mark Brown
2019-04-11 16:42 ` [PATCH v4 3/4] spi/spi-bcm2835: Remove DMA transfer size cap Noralf Trønnes
2019-04-11 16:42 ` [PATCH v4 4/4] drm/tinydrm: Remove chunk splitting in tinydrm_spi_transfer Noralf Trønnes

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