From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752374AbbKKIMX (ORCPT ); Wed, 11 Nov 2015 03:12:23 -0500 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:44320 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752282AbbKKIMU (ORCPT ); Wed, 11 Nov 2015 03:12:20 -0500 Date: Wed, 11 Nov 2015 09:12:15 +0100 From: Sascha Hauer To: Anton Bondarenko 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 Message-ID: <20151111081215.GQ8526@pengutronix.de> References: <1446388901-6073-1-git-send-email-anton.bondarenko.sama@gmail.com> <1446388901-6073-3-git-send-email-anton.bondarenko.sama@gmail.com> <20151105084723.GI8526@pengutronix.de> <56425176.9060805@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56425176.9060805@gmail.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 09:11:03 up 24 days, 16:50, 53 users, load average: 0.01, 0.04, 0.05 User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 |