On Tue, Nov 10, 2015 at 09:20:06PM +0100, Anton Bondarenko wrote: > > > On 05.11.2015 09:47, Sascha Hauer wrote: > >>@@ -890,12 +891,40 @@ static void spi_imx_dma_tx_callback(void *cookie) > >> complete(&spi_imx->dma_tx_completion); > >> } > >> > >>+static int spi_imx_calculate_timeout(struct spi_imx_data *spi_imx, int size) > >>+{ > >>+ unsigned long coef1 = 1; > >>+ unsigned long coef2 = MSEC_PER_SEC; > >>+ unsigned long timeout = 0; > >>+ > >>+ /* Swap coeficients to avoid div by 0 */ > >>+ if (spi_imx->spi_bus_clk < MSEC_PER_SEC) { > >>+ coef1 = MSEC_PER_SEC; > >>+ coef2 = 1; > >>+ } > >>+ > >>+ /* Time with actual data transfer */ > >>+ timeout += DIV_ROUND_UP(8 * size * coef1, > >>+ spi_imx->spi_bus_clk / coef2); > >>+ > >>+ /* Take CS change delay related to HW */ > >>+ timeout += DIV_ROUND_UP((size - 1) * 4 * coef1, > >>+ spi_imx->spi_bus_clk / coef2); > >>+ > >>+ /* Add extra second for scheduler related activities */ > >>+ timeout += MSEC_PER_SEC; > >>+ > >>+ /* Double calculated timeout */ > >>+ return msecs_to_jiffies(2 * timeout); > >>+} > > > >I think you can simplify this function to: > > > > timeout = size * 8 / spi_imx->spi_bus_clk; > > timeout += 2; > > > > return msecs_to_jiffies(timeout * MSEC_PER_SEC); > > > >The rationale is that when size * 8 / spi_imx->spi_bus_clk is 0 then we > >can add another second and be fine. No need to calculate this more > >accurate, in the end it's important to catch the timeout. If we do this > >one or two seconds too late doesn't matter. > > > >Sascha > > > > Sascha, > > What about something like this: > timeout = size * (8 + 4) / spi_imx->spi_bus_clk; > timeout += 2; > > return msecs_to_jiffies(2 * timeout * MSEC_PER_SEC); > > I think we still need to take into account 4 CLKs between each burst. Fine with me. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html