From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian Norris Date: Sat, 19 Dec 2015 02:27:37 +0000 Subject: Re: [PATCH] mtd: sh_flctl: pass FIFO as physical address Message-Id: <20151219022737.GC109450@google.com> List-Id: References: <3152458.D3kElfhRW2@wuerfel> In-Reply-To: <3152458.D3kElfhRW2@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Tue, Dec 08, 2015 at 04:38:12PM +0100, Arnd Bergmann wrote: > By convention, the FIFO address we pass using dmaengine_slave_config > is a physical address in the form that is understood by the DMA > engine, as a dma_addr_t, phys_addr_t or resource_size_t. > > The sh_flctl driver however passes a virtual __iomem address that > gets cast to dma_addr_t in the slave driver. This happens to work > on shmobile because that platform sets up an identity mapping for > its MMIO regions, but such code is not portable to other platforms, > and prevents us from ever changing the platform mapping or reusing > the driver on other architectures like ARM64 that might not have the > mapping. > > We also get a warning about a type mismatch for the case that > dma_addr_t is wider than a pointer, i.e. when CONFIG_LPAE is set: > > drivers/mtd/nand/sh_flctl.c: In function 'flctl_setup_dma': > drivers/mtd/nand/sh_flctl.c:163:17: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] > cfg.dst_addr = (dma_addr_t)FLDTFIFO(flctl); > > This changes the driver to instead pass the physical address of > the FIFO that is extracted from the MMIO resource, making the > code more portable and avoiding the warning. > > Signed-off-by: Arnd Bergmann Applied