Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757542AbbKFP7h (ORCPT ); Fri, 6 Nov 2015 10:59:37 -0500 Received: from eusmtp01.atmel.com ([212.144.249.243]:18088 "EHLO eusmtp01.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752343AbbKFP7g (ORCPT ); Fri, 6 Nov 2015 10:59:36 -0500 From: Ludovic Desroches To: , , CC: , , , , , , Ludovic Desroches Subject: [PATCH 0/2] mmc: sdhci: potentially bad behavior when using vmmc supply Date: Fri, 6 Nov 2015 16:59:28 +0100 Message-ID: <1446825570-30029-1-git-send-email-ludovic.desroches@atmel.com> X-Mailer: git-send-email 2.5.0 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3266 Lines: 81 Hi, I would like to have some feedback for these two patches. I have two questions. 1. To suppress the warnings telling me I have no vmmc and vqmmc supplies, I have added them and discovered that adding a vmmc supply involve only writing 1 in the Power Control Register involves enabling the SD Bus Power with a non valid value for the SD Bus Voltage. If the host controllers strictly follows the specification, it shall not enable SD Bus Power. So enough if it seems useless to configure SD Bus Voltage because we have an external regulator, do it. By the way, I am curious to understand what is really the SD Bus Voltage. I mean talking about bus voltage makes me thinking more about vqmmc than vmmc. Is it only bad naming or do I miss something? >From the specification, there is this figure: HOST --------------------------------------------------- | ------------ 3.3V | VDD | | Power SW |------------------------------------|---------- | ------------ | | | | ---------| | | | | | | | -------------- ---------------------- | | | Ref. Volt. |-----| Regulator/Selector | | | -------------- ---------------------- | | 3.3V/1.8V | | | | | | |--------------- | | | | | | | | | R R _ | | | | | _ | | | | | | | | | | | /// | | ------- | | | CLK | | |----)--)------|---------- | ----------------------- |Multi| | | | CMD | |Random Logic Circuits|---|Drive|----)---------|---------- | ----------------------- |I/O | | | DAT | | |--------------|---------- | ------- | --------------------------------------------------- In my mind vmmc is the 3.3V signal and vqmmc is the 3.3V/1.8V signal, so why talking about bus voltage? 2. Is the regulator-gpio usage the right thing to do for vqmmc? In my case it is not really driven by a gpio but by a pio from the sdhci device. In the binding, declaring the gpio is an option so I thought using this regulator fits my need. P.S. patch 2 is based on another patch not yet in next: http://www.spinics.net/lists/arm-kernel/msg453447.html Thanks Ludovic Ludovic Desroches (2): mmc: sdhci: set bus voltage before enabling bus power ARM: at91/dt: sama5d2 Xplained: add regulators for sdhci devices arch/arm/boot/dts/at91-sama5d2_xplained.dts | 14 ++++++++++++++ drivers/mmc/host/sdhci.c | 7 ------- 2 files changed, 14 insertions(+), 7 deletions(-) -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/