On Sun, 23 Feb 2020 at 15:45, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > On 2/23/20 3:00 AM, Antti Seppälä wrote: > > Hi Guenter, > > > > On Wed, 19 Feb 2020 at 23:11, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > >> > >> Yes, those patches didn't address the core problem. Can you test with the > >> attached two patches ? > >> > >> Thanks, > >> Guenter > > > > I took a look at your patch (usb: dwc2: Simplify DMA alignment code) > > and I don't believe it is correct. > > > > The patch re-introduces the dma_aligned_buffer struct and takes some > > care to align the beginning of the struct to dma cache lines. However > > we should be aligning the data[0] pointer inside the struct instead. > > With the code in the patch data[0] gets pushed to be at an offset from > > the alignment by kmalloc_ptr and old_xfer_buffer pointers. In other > > words data[0] is now not aligned to dma cache boundaries. > > > > I thought so too initially. However, > > temp = PTR_ALIGN(kmalloc_ptr + 1, TEGRA_USB_DMA_ALIGN) - 1; > > aligns the structure pointer such that its _end_ is DMA-aligned, > which is ->data[0]. > Hmm, looks like you're right. I somehow missed the - 1 at the end. Sorry for the noise I guess. Would be nice to know what makes the previous code prone to pointer corruption issues though. With the added padding that pointer should also be on another dma cache line. -- Antti
