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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e On 10/27/26 10:14, Andy Shevchenko wrote: > On Tue, Oct 27, 2026 at 09:41:17AM -0700, Florian Fainelli wrote: >> On 10/27/26 08:10, Andy Shevchenko wrote: >>> On Tue, Oct 27, 2026 at 12:06:35PM +0100, Greg Kroah-Hartman wrote: >>>> >>>> The local variable daddr is declared as u32 but assigned from dma_addr_t >>>> fields (priv->rx_addr and priv->tx_addr), which are 64-bit on ARM64. >>>> This silently truncates the upper 32 bits, causing upper_32_bits(daddr) >>>> to always produce zero when programming the UART DMA descriptor high >>>> address registers. Change the type to dma_addr_t to preserve the full >>>> DMA address. >>> >>> Since this value goes to HW, it should be u64. Even on 32-bit machines there >>> are possibilities to cover a bigger address space / DMA space. >> >> That is one way to go about it, but since the size of dma_addr_t follows >> ARCH_DMA_ADDR_T_64BIT, we could also take this patch, and also make the >> upper 32-bits programming conditional upon CONFIG_ARCH_DMA_ADDR_T_64BIT. > > You never know this. The use of u64 is simple as that: it goes to HW as 64-bit > value no matter what. Note, in the past we used to have a problematic use of > dma_addr_t exactly due to its dependency on the data bus size when programming > HW, and hence, based on my experience, I hardly recommend not to use dma_addr_t > in this case, use plain fixed u64. It's not a hot path where optimizing for bus transactions would make sense, so I guess it's fine to use u64 and have the two halves programmed accordingly. -- Florian