Messages in this thread | | | From | Arnd Bergmann <> | Date | Wed, 11 Oct 2017 16:39:04 +0200 | Subject | Re: [PATCH] dmaengine: stm32-mdma: avoid 64-bit division |
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On Wed, Oct 11, 2017 at 4:27 PM, Benjamin Gaignard <benjamin.gaignard@linaro.org> wrote: > 2017-10-11 16:01 GMT+02:00 Arnd Bergmann <arnd@arndb.de>: > >> @@ -398,6 +400,9 @@ static enum dma_slave_buswidth stm32_mdma_get_max_width(u32 buf_len, u32 tlen) >> break; >> } >> >> + if (addr % max_width) >> + max_width = DMA_SLAVE_BUSWIDTH_1_BYTE; >> + > > I'm only half-convince by the implicite 32 bits cast done into > function prototype. > If we keep using dma_addr_t and use do_div() instead of % > does compiler can still optimize the code ? >
I wouldn't want to add a do_div() here, since it's guaranteed not to be needed. Would you prefer an explicit cast here and leave the argument as dma_addr_t?
We could also use a bit mask here like
if (addr & (max_width-1))
or we could combined it with the check above:
if ((((buf_len | addr) & (max_width - 1)) == 0) && (tlen >= max_width))
Arnd
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