Messages in this thread | | | Subject | Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one | From | Anton Bondarenko <> | Date | Tue, 10 Nov 2015 21:20:06 +0100 |
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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.
Regards, Anton
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