Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752985AbaGJJmJ (ORCPT ); Thu, 10 Jul 2014 05:42:09 -0400 Received: from mail-lb0-f177.google.com ([209.85.217.177]:36311 "EHLO mail-lb0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752923AbaGJJmE (ORCPT ); Thu, 10 Jul 2014 05:42:04 -0400 MIME-Version: 1.0 In-Reply-To: References: <1404982207-4707-1-git-send-email-harinik@xilinx.com> <1404982207-4707-2-git-send-email-harinik@xilinx.com> Date: Thu, 10 Jul 2014 11:42:01 +0200 X-Google-Sender-Auth: ukN832l1tJ_K8-I-t6NixX_cp0I Message-ID: Subject: Re: [RFC PATCH 1/2] spi: Add support for Zynq QSPI controller From: Geert Uytterhoeven To: Harini Katakam Cc: Mark Brown , Grant Likely , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , linux-spi , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-doc@vger.kernel.org" , David Woodhouse , Brian Norris , =?UTF-8?B?TWFyZWsgVmHFoXV0?= , Artem Bityutskiy , Geert Uytterhoeven , Sascha Hauer , Jingoo Han , Sourav Poddar , "michals@xilinx.com" , Punnaiah Choudary Kalluri Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Harini, On Thu, Jul 10, 2014 at 11:31 AM, Harini Katakam wrote: >>> + master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_RX_DUAL | SPI_RX_QUAD | >>> + SPI_TX_DUAL | SPI_TX_QUAD; >> >> Your driver advertises Dual/Quad SPI Transfer capabilities, but it doesn't >> check spi_transfer.[tr]x_nbits? How can it determine when to enable Dual/Quad? > > Here the driver is just giving information that the controller support it. > The MTD layer enables dual/quad based on what the flash supports; quad > being the first priority > I understand that the spi core reads rx, tx-bus-width property and > master support flags and > performs the necessary checks. That's correct: as long as the rx, tx-bus-width properties do not indicate a Dual or Quad wiring, it won't be used. However, based on schematics, someone may set the rx, tx-bus-width properties to 4, which is correct, as DT describes the hardware. But this will fail to work. So I think it's safer not to announce Dual/Quad support in the driver until the actual driver support is there. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- 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/