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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD650C7EE23 for ; Thu, 8 Jun 2023 11:52:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236045AbjFHLwR (ORCPT ); Thu, 8 Jun 2023 07:52:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232417AbjFHLwQ (ORCPT ); Thu, 8 Jun 2023 07:52:16 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBE2FE50 for ; Thu, 8 Jun 2023 04:52:15 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7124764CA8 for ; Thu, 8 Jun 2023 11:52:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 864CFC433EF; Thu, 8 Jun 2023 11:52:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1686225134; bh=OEhDGVhpQC0gZVXCvMuGDXNf8DruYlXOsTcmJpeZFUY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kOLTdOW68oc5TN2o6GFg0+BU+Bu3SyODvqJDAIH8CcRmh2yHexmiOwhEGofy1RZbm rLMJ2vbruqeU5s0nKjr/etLVRIPzRczaDRL+tgxuxZvjodxcSOBXn4Uzs9jItXYhis vJ/Y+Wzj//DH510Ek1isoUNxO5dc4dPxm3K0i5JU= Date: Thu, 8 Jun 2023 13:52:12 +0200 From: Greg KH To: Robert Hodaszi Cc: jirislaby@kernel.org, linux-serial@vger.kernel.org, sherry.sun@nxp.com Subject: Re: [PATCH] tty: serial: fsl_lpuart: reduce RX watermark to 0 on LS1028A Message-ID: <2023060858-groove-riddance-0c09@gregkh> References: <20230608111927.1808525-1-robert.hodaszi@digi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230608111927.1808525-1-robert.hodaszi@digi.com> Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Thu, Jun 08, 2023 at 01:19:27PM +0200, Robert Hodaszi wrote: > LS1028A is using DMA with LPUART. Having RX watermark set to 1, means > DMA transactions are started only after receiving the second character. > > On other platforms with newer LPUART IP, Receiver Idle Empty function > initiates the DMA request after the receiver is idling for 4 characters. > But this feature is missing on LS1028A, which is causing a 1-character > delay in the RX direction on this platform. > > Set RX watermark to 0 to initiate RX DMA after each character. > > Signed-off-by: Robert Hodaszi What commit id does this fix? Should it go to stable releases? thanks, greg k-h