From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9BD0C43331 for ; Wed, 1 Apr 2020 16:36:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6363F20772 for ; Wed, 1 Apr 2020 16:36:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585758988; bh=T7EptmKtFcmwZNYtW2NJwIhPk4hbrAUxmdJ1+Wx/nAc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=t009SwpuLwJZU0M11KgrQFBeFKO8fU7DYAwHL8Vkb/npM4t1QMrLDvWsJqiKdzYLK ufcxg9dPL7ifYNOyWVYXM8WusolSBrtpqGJ54rKPHbGT07HxWJkDQ1ZB5yoUY2jzA8 T1kisNuPGupELIaGOdqKIKIp2Q1fRRiK4K8gkp58= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732342AbgDAQg1 (ORCPT ); Wed, 1 Apr 2020 12:36:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:35250 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388056AbgDAQgW (ORCPT ); Wed, 1 Apr 2020 12:36:22 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 34AD220772; Wed, 1 Apr 2020 16:36:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585758981; bh=T7EptmKtFcmwZNYtW2NJwIhPk4hbrAUxmdJ1+Wx/nAc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jG6/C39TasmKGfKX4F0sY9t3CfSrgWPg3eo7jz0EtwZjDgl00NR78treVC3US2lfu ZXytUjGouJ9Lq/1wnPEXmIj66AdAZoVY2cI3+VAjvyMRR0W0lZz1Uo4FghuKrnmCtr LaCm+qs8WkGvVdRzdb2itQSoKBM3WhVoh12b+dnY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thommy Jakobsson , Naga Sureshkumar Relli , Mark Brown , Sasha Levin Subject: [PATCH 4.9 004/102] spi/zynqmp: remove entry that causes a cs glitch Date: Wed, 1 Apr 2020 18:17:07 +0200 Message-Id: <20200401161532.417694260@linuxfoundation.org> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200401161530.451355388@linuxfoundation.org> References: <20200401161530.451355388@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thommy Jakobsson [ Upstream commit 5dd8304981ecffa77bb72b1c57c4be5dfe6cfae9 ] In the public interface for chipselect, there is always an entry commented as "Dummy generic FIFO entry" pushed down to the fifo right after the activate/deactivate command. The dummy entry is 0x0, irregardless if the intention was to activate or deactive the cs. This causes the cs line to glitch rather than beeing activated in the case when there was an activate command. This has been observed on oscilloscope, and have caused problems for at least one specific flash device type connected to the qspi port. After the change the glitch is gone and cs goes active when intended. The reason why this worked before (except for the glitch) was because when sending the actual data, the CS bits are once again set. Since most flashes uses mode 0, there is always a half clk period anyway for cs to clk active setup time. If someone would rely on timing from a chip_select call to a transfer_one, it would fail though. It is unknown why the dummy entry was there in the first place, git log seems to be of no help in this case. The reference manual gives no indication of the necessity of this. In fact the lower 8 bits are a setup (or hold in case of deactivate) time expressed in cycles. So this should not be needed to fulfill any setup/hold timings. Signed-off-by: Thommy Jakobsson Reviewed-by: Naga Sureshkumar Relli Link: https://lore.kernel.org/r/20200224162643.29102-1-thommyj@gmail.com Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/spi/spi-zynqmp-gqspi.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/spi/spi-zynqmp-gqspi.c b/drivers/spi/spi-zynqmp-gqspi.c index 18aeaceee2862..d26c0eda2d9ea 100644 --- a/drivers/spi/spi-zynqmp-gqspi.c +++ b/drivers/spi/spi-zynqmp-gqspi.c @@ -415,9 +415,6 @@ static void zynqmp_qspi_chipselect(struct spi_device *qspi, bool is_high) zynqmp_gqspi_write(xqspi, GQSPI_GEN_FIFO_OFST, genfifoentry); - /* Dummy generic FIFO entry */ - zynqmp_gqspi_write(xqspi, GQSPI_GEN_FIFO_OFST, 0x0); - /* Manually start the generic FIFO command */ zynqmp_gqspi_write(xqspi, GQSPI_CONFIG_OFST, zynqmp_gqspi_read(xqspi, GQSPI_CONFIG_OFST) | -- 2.20.1