From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f194.google.com ([74.125.82.194]:36180 "EHLO mail-ot0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751416AbdBFTi0 (ORCPT ); Mon, 6 Feb 2017 14:38:26 -0500 Received: by mail-ot0-f194.google.com with SMTP id 36so11577587otx.3 for ; Mon, 06 Feb 2017 11:38:26 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <20170204213931.3566-1-marex@denx.de> From: Fabio Estevam Date: Mon, 6 Feb 2017 17:38:25 -0200 Message-ID: Subject: Re: [PATCH] serial: imx: Only enable UART DMA on i.MX6Q and i.MX53 To: Marek Vasut Cc: Fabio Estevam , "linux-arm-kernel@lists.infradead.org" , Kai Ruhnau , "# 4 . 9+" , Martyn Welch , Shawn Guo , Clemens Gruber , Tim Harvey Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: Hi Marek, On Mon, Feb 6, 2017 at 5:05 PM, Marek Vasut wrote: > Well yes, DMA is broken in 4.9 , that's why it's CC stable 4.9+ :) This patch is based on the fact that the UART on the imx6sx is not of a imx6q UART type, which is not correct. Current imx6sx.dtsi misses to add a "fsl,imx6q-uart" compatible string, just like all other imx6 SoC dtsi. When we fix the compatible uart problem on imx6sx.dtsi, then DMA will be enabled and things will break again. That's why we need a better fix for this issue: 1) Let's see if Clemens' suggestion of using the latest SDMA firmware can make DMA robust on your usecase. 2) If the system fails even with the latest SDMA, then the board dts can disable dma by passing empty dma nodes. Not all mx6 system seem to suffer from such SDMA problem. On a imx6sx-udoo-neo we could use UART with DMA to connect to the Bluetooth chip. Thanks From mboxrd@z Thu Jan 1 00:00:00 1970 From: festevam@gmail.com (Fabio Estevam) Date: Mon, 6 Feb 2017 17:38:25 -0200 Subject: [PATCH] serial: imx: Only enable UART DMA on i.MX6Q and i.MX53 In-Reply-To: References: <20170204213931.3566-1-marex@denx.de> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Marek, On Mon, Feb 6, 2017 at 5:05 PM, Marek Vasut wrote: > Well yes, DMA is broken in 4.9 , that's why it's CC stable 4.9+ :) This patch is based on the fact that the UART on the imx6sx is not of a imx6q UART type, which is not correct. Current imx6sx.dtsi misses to add a "fsl,imx6q-uart" compatible string, just like all other imx6 SoC dtsi. When we fix the compatible uart problem on imx6sx.dtsi, then DMA will be enabled and things will break again. That's why we need a better fix for this issue: 1) Let's see if Clemens' suggestion of using the latest SDMA firmware can make DMA robust on your usecase. 2) If the system fails even with the latest SDMA, then the board dts can disable dma by passing empty dma nodes. Not all mx6 system seem to suffer from such SDMA problem. On a imx6sx-udoo-neo we could use UART with DMA to connect to the Bluetooth chip. Thanks