Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] mmc: dw_mmc: use resource_size_t to store physical address | Date | Wed, 18 Nov 2015 16:45:23 +0100 |
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On Wednesday 18 November 2015 17:29:19 Andy Shevchenko wrote: > > I understand most of the things here, what I don't is how a platform > is supposed to work if you have the following: > a) HW, that uses register space let's say higher than 32-bit; > b) DMA engine, which should provide a DMA capability for above HW block; > c) dma_addr_t which does not cover the HW register space.
On this platform, the current code is obviously broken, because the pointer is 32-bit wide and cannot reach the registers. I assume you agree on that part.
With my patch, the 64-bit resource_size_t in dw_mci helps get the correct FIFO address to this line:
cfg.dst_addr = host->phy_regs + fifo_offset;
There, it remains broken because of the dma_addr_t being too short, and we also need Linus' patch from https://lkml.org/lkml/2013/4/26/120 in addition to mine.
> For me it clearly looks like a platform (HW / SW) configuration issue.
I think some people have argued in the past that we should always use the same type for dma_addr_t, resource_size_t and phys_addr_t. That would certainly fix the problem you describe as well. In practice, everyone has that already, and my patch by itself fixes all the cases where the FIFO is at a high address and dma_addr_t is already 64-bit wide.
> In case of bounce buffers I can't understand how it helps there.
Right, bounce buffers are irrelevant here, because the FIFO address is never translated and never bounced.
Arnd
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