From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@lst.de>, Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Baoquan He <bhe@redhat.com>,
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Subject: RE: [PATCH 22/22] mtd: rawnand: Use dma_alloc_noncoherent() for dma buffer
Date: Tue, 22 Feb 2022 09:06:48 +0000 [thread overview]
Message-ID: <fe8deb6dd0b44a8a839820747451c37c@AcuMS.aculab.com> (raw)
In-Reply-To: <20220222084652.GB6210@lst.de>
From: Christoph Hellwig
> Sent: 22 February 2022 08:47
...
> > Hmm.. for this specific case, What about allocating two buffers
> > for DMA_TO_DEVICE and DMA_FROM_DEVICE at initialization time?
>
> That will work, but I don't see the benefit as you'd still need to call
> dma_sync_single* before and after each data transfer.
For systems with an iommu that should save all the iommu setup
for every transfer.
I'd also guess that it saves worrying about the error path
when the dma_map fails (eg because the iommu has no space).
OTOH the driver would be 'hogging' iommu space, so maybe
allocate during open() (or equivalent).
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-02-22 9:06 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-19 0:51 [PATCH 00/22] Don't use kmalloc() with GFP_DMA Baoquan He
2022-02-19 0:52 ` [PATCH 01/22] parisc: pci-dma: remove stale code and comment Baoquan He
2022-02-19 7:07 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 02/22] net: moxa: Don't use GFP_DMA when calling dma_alloc_coherent() Baoquan He
2022-02-19 7:07 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 03/22] gpu: ipu-v3: " Baoquan He
2022-02-19 7:07 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 04/22] drm/sti: Don't use GFP_DMA when calling dma_alloc_wc() Baoquan He
2022-02-19 7:08 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 05/22] sound: n64: Don't use GFP_DMA when calling dma_alloc_coherent() Baoquan He
2022-02-19 7:08 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 06/22] fbdev: da8xx: " Baoquan He
2022-02-19 7:08 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 07/22] fbdev: mx3fb: Don't use GFP_DMA when calling dma_alloc_wc() Baoquan He
2022-02-19 7:08 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 08/22] usb: gadget: lpc32xx_udc: Don't use GFP_DMA when calling dma_alloc_coherent() Baoquan He
2022-02-19 7:09 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 09/22] usb: cdns3: " Baoquan He
2022-02-19 7:09 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 10/22] uio: pruss: " Baoquan He
2022-02-19 7:09 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 11/22] staging: emxx_udc: " Baoquan He
2022-02-19 6:51 ` Wolfram Sang
2022-02-20 1:55 ` Baoquan He
2022-02-19 7:09 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 12/22] " Baoquan He
2022-02-19 7:10 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 13/22] spi: atmel: " Baoquan He
2022-02-19 7:10 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 14/22] spi: spi-ti-qspi: " Baoquan He
2022-02-19 7:12 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 15/22] usb: cdns3: Don't use GFP_DMA32 when calling dma_pool_alloc() Baoquan He
2022-02-19 7:13 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 16/22] usb: udc: lpc32xx: Don't use GFP_DMA " Baoquan He
2022-02-19 7:13 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 17/22] net: marvell: prestera: " Baoquan He
2022-02-19 4:54 ` Jakub Kicinski
2022-02-20 2:06 ` Baoquan He
2022-02-19 7:13 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 18/22] net: ethernet: mtk-star-emac: Don't use GFP_DMA when calling dmam_alloc_coherent() Baoquan He
2022-02-19 7:13 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 19/22] ethernet: rocker: Use dma_alloc_noncoherent() for dma buffer Baoquan He
2022-02-19 7:14 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 20/22] HID: intel-ish-hid: " Baoquan He
2022-02-19 7:14 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 21/22] mmc: wbsd: " Baoquan He
2022-02-19 7:17 ` Christoph Hellwig
2022-02-20 8:40 ` Baoquan He
2022-02-22 8:45 ` Christoph Hellwig
2022-02-22 9:14 ` Baoquan He
2022-02-22 13:11 ` Christoph Hellwig
2022-02-22 13:40 ` Baoquan He
2022-02-22 13:41 ` [PATCH 1/2] dma-mapping: check dma_mask for streaming mapping allocs Baoquan He
2022-02-22 15:59 ` Christoph Hellwig
2022-02-23 0:28 ` Baoquan He
2022-02-23 14:25 ` Christoph Hellwig
2022-02-23 14:57 ` David Laight
2022-02-24 14:11 ` Baoquan He
2022-02-24 14:27 ` David Laight
2022-02-25 15:39 ` 'Baoquan He'
2022-02-22 13:42 ` [PATCH 2/2] kernel/dma: rename dma_alloc_direct and dma_map_direct Baoquan He
2022-02-22 15:59 ` Christoph Hellwig
2022-02-19 0:52 ` [PATCH 22/22] mtd: rawnand: Use dma_alloc_noncoherent() for dma buffer Baoquan He
2022-02-19 7:19 ` Christoph Hellwig
2022-02-19 11:18 ` Hyeonggon Yoo
2022-02-22 8:46 ` Christoph Hellwig
2022-02-22 9:06 ` David Laight [this message]
2022-02-22 13:16 ` 'Christoph Hellwig'
2022-02-21 13:57 ` [PATCH 00/22] Don't use kmalloc() with GFP_DMA Heiko Carstens
2022-02-22 8:44 ` Christoph Hellwig
2022-02-22 13:12 ` Baoquan He
2022-02-22 13:26 ` Baoquan He
2022-02-23 19:18 ` Heiko Carstens
2022-02-24 6:33 ` Christoph Hellwig
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