From: Anton Bondarenko <anton.bondarenko.sama@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: broonie@kernel.org, b38343@freescale.com,
linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
vladimir_zapolskiy@mentor.com, jiada_wang@mentor.com
Subject: Re: [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one
Date: Tue, 10 Nov 2015 21:20:06 +0100 [thread overview]
Message-ID: <56425176.9060805@gmail.com> (raw)
In-Reply-To: <20151105084723.GI8526@pengutronix.de>
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
next prev parent reply other threads:[~2015-11-10 20:20 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-01 14:41 [PATCH v3 0/7] Improvements for SPI IMX driver for Freescale IMX51, IMX53 and IMX6 Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 1/7] spi: imx: Fix DMA transfer Anton Bondarenko
2015-11-03 7:08 ` Robin Gong
2015-11-04 21:03 ` Anton Bondarenko
2015-11-05 8:34 ` Sascha Hauer
2015-11-05 16:51 ` Anton Bondarenko
2015-11-14 10:02 ` Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 2/7] spi: imx: replace fixed timeout with calculated one Anton Bondarenko
2015-11-05 8:47 ` Sascha Hauer
2015-11-10 20:20 ` Anton Bondarenko [this message]
2015-11-11 8:12 ` Sascha Hauer
2015-11-14 10:01 ` Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 3/7] spi: imx: add support for all SPI word width for DMA transfer Anton Bondarenko
2015-11-14 10:08 ` Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 4/7] spi: imx: add function to check for IMX51 family controller Anton Bondarenko
2015-11-14 10:06 ` Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 5/7] spi: imx: Add support for loopback for ECSPI controllers Anton Bondarenko
2015-11-14 10:06 ` Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 6/7] spi: imx: return error from dma channel request Anton Bondarenko
2015-11-05 8:56 ` Sascha Hauer
2015-11-05 16:00 ` Anton Bondarenko
2015-11-14 10:03 ` Anton Bondarenko
2015-11-14 10:05 ` Anton Bondarenko
2015-11-01 14:41 ` [PATCH v3 7/7] spi: imx: defer spi initialization, if DMA engine is pending Anton Bondarenko
2015-11-05 8:59 ` Sascha Hauer
2015-11-05 16:18 ` Anton Bondarenko
2015-11-14 10:03 ` Anton Bondarenko
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