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 1bPYhe-0002Ts-N6 for barebox@lists.infradead.org; Tue, 19 Jul 2016 17:21:09 +0000 Date: Tue, 19 Jul 2016 19:18:35 +0200 (CEST) From: Alexander Kurz Message-ID: MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: mc13xxx: Define maximum SPI clock frequency global to driver To: Alexander Shiyan , Sascha Hauer Cc: barebox@lists.infradead.org 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? Cheers, Alexander _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox