From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from vs81.iboxed.net ([185.82.85.146]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bPbiU-00022b-2E for barebox@lists.infradead.org; Tue, 19 Jul 2016 20:34:11 +0000 Date: Tue, 19 Jul 2016 22:31:49 +0200 (CEST) From: Alexander Kurz In-Reply-To: <1468952131.496358501@f380.i.mail.ru> Message-ID: References: <1468952131.496358501@f380.i.mail.ru> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-598520180-2011066681-1468960309=:10923" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: mc13xxx: Define maximum SPI clock frequency global to driver To: Alexander Shiyan Cc: barebox@lists.infradead.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---598520180-2011066681-1468960309=:10923 Content-Type: TEXT/PLAIN; charset="utf-8" Content-Transfer-Encoding: 8bit On Tue, 19 Jul 2016, Alexander Shiyan wrote: > >Вторник, 19 июля 2016, 20:18 +03:00 от Alexander Kurz : > > > >Hi, > >I just ran into a problem resulting from patch 6e18b3a48ee4 > >("mc13xxx: Define maximum SPI clock frequency global to driver"). > > > >On a kindle2 board the SPI communication between an iMX31 and a MC13783 > >won't work at 20MHz. Unfortunately both ICs are BGA mounted blocking any > >access with scope probes. Attempts to tweak the pad properties to > >PAD_CTL_DRV_HIGH | PAD_CTL_SRE_FAST | PAD_CTL_100K_PU > >did not solve the problem - anyway this is a battery powered device where > >the original implementers took great care on long battery life, > >e.g. PAD_CTL_DRV_HIGH should not be nessesary for PMIC control. > > > >I do not see any way to override the 20MHz bitrate from board code, and > >since the PMIC access is not time critical on an ebook-reader my choice > >would be rather 200kHz. > > > >Is there any way to override the driver supplied default max_speed_hz? > >If not, my proposal is to either > >* revert this patch and let the board code choose frequency > >or > >* reduce the speed to some common acceptable rate, e.g. 6MHz are fine > > > >How was this solved with other SPI devices? > > For me, the MC13783 with i.MX27 works fine with 20MHz. > Anyway, you can change line in mc13xxx driver to: > mc_dev->spi->max_speed_hz = mc_dev->spi->max_speed_hz ? : 20000000; > So you can use struct spi_board_info field for specify exact frequency. Perfect, this provides the default but provides the option to override it. I'll send a patch for this, thanks, Alexander ---598520180-2011066681-1468960309=:10923 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox ---598520180-2011066681-1468960309=:10923--