From mboxrd@z Thu Jan 1 00:00:00 1970 From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni) Date: Thu, 25 Oct 2012 13:43:52 +0200 Subject: [PATCH 1/2] arm: mvebu: increase atomic coherent pool size for armada 370/XP In-Reply-To: <201210251127.36960.arnd@arndb.de> References: <1351086561-13569-1-git-send-email-gregory.clement@free-electrons.com> <1351086561-13569-2-git-send-email-gregory.clement@free-electrons.com> <201210251127.36960.arnd@arndb.de> Message-ID: <20121025134352.16a8ef81@skate> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Arnd, On Thu, 25 Oct 2012 11:27:36 +0000, Arnd Bergmann wrote: > On Wednesday 24 October 2012, Gregory CLEMENT wrote: > > For Armada 370/XP we have the same problem that for the commit > > cb01b63, so we applied the same solution: "The default 256 KiB > > coherent pool may be too small for some of the Kirkwood devices, so > > increase it to make sure that devices will be able to allocate their > > buffers with GFP_ATOMIC flag" > > > > Signed-off-by: Gregory CLEMENT > > Do you know why the ATA driver needs this? I find it surprising that > it's necessary, so I'd like to make sure we're not just working around > a device driver bug here. The sata_mv driver create dma_pool and allocate objects from them, and all the memory allocated for dma_pools is allocated using dma_alloc_coherent(), and I guess the driver is using too much of them. Seems like the driver is too lazy and allocates everything coherent to avoid the hassle of doing dma_map/dma_unmap operations when needed, but I haven't looked in details at the driver yet to see if it would be possible to switch those DMA coherent allocations into non-coherent allocations + appropriate calls to the DMA operations. That said, that's for sure a larger task than just enabling SATA on Armada 370/XP, so I would advocate to handle this problem separately. Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com