Messages in this thread | | | Date | Fri, 15 May 2020 17:01:29 +0300 | From | Andy Shevchenko <> | Subject | Re: [PATCH v2 09/19] spi: dw: Parameterize the DMA Rx/Tx burst length |
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On Fri, May 15, 2020 at 01:47:48PM +0300, Serge Semin wrote: > It isn't good to have numeric literals in the code especially if there > are multiple of them and they are related. Moreover in current > implementation the Tx DMA transfer activation level isn't optimal, > since it's hardwired to be at 16-32 bytes level, while it's better > to keep the SPI FIFO buffer as full as possible until all available > data is submitted. So lets introduce the DMA burst level > parametrization macros with optimal values - issue Rx transfer if at > least 16 bytes are available in the buffer and execute Tx transaction > if at least 16 bytes room is opened in SPI Tx FIFO.
> - dw_writel(dws, DW_SPI_DMARDLR, 0xf); > - dw_writel(dws, DW_SPI_DMATDLR, 0x10); > + dw_writel(dws, DW_SPI_DMARDLR, RX_BURST_LEVEL - 1); > + dw_writel(dws, DW_SPI_DMATDLR, dws->fifo_len - TX_BURST_LEVEL);
...and if FIFO length is less than TX_BURST_LEVEL?
For the patch that introduces definitions, i.e. keeping the last line here as
dw_writel(dws, DW_SPI_DMATDLR, TX_BURST_LEVEL);
I'm good. You may put your tag in that case. For fifo_len case we need to discuss in separate patch, perhaps.
-- With Best Regards, Andy Shevchenko
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