From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755400AbeDCLWi (ORCPT ); Tue, 3 Apr 2018 07:22:38 -0400 Received: from gstat2.m.smailru.net ([94.100.177.128]:51618 "EHLO fallback.mail.ru" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755121AbeDCLWg (ORCPT ); Tue, 3 Apr 2018 07:22:36 -0400 Subject: Re: [PATCH 2/6] spi: sun4i: restrict transfer length in PIO-mode To: Maxime Ripard Cc: Mark Brown , Chen-Yu Tsai , linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20180329185907.27281-1-ssuloev@orpaltech.com> <20180329185907.27281-3-ssuloev@orpaltech.com> <20180403081041.3ully6bcyfwx2cx6@flea> From: Sergey Suloev Message-ID: <4390604e-092b-a89d-3581-b57ee9cbb6a1@orpaltech.com> Date: Tue, 3 Apr 2018 14:08:43 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180403081041.3ully6bcyfwx2cx6@flea> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-7FA49CB5: 0D63561A33F958A5BE0F62698ACAEC23D7076D3B86F44C0254CC0BFB986C5EF1725E5C173C3A84C30584FF81F342DA070BF47669B41AB5238734EF69C36C4A4DC4224003CC836476C0CAF46E325F83A50BF2EBBBDD9D6B0F5D41B9178041F3E72623479134186CDE6BA297DBC24807EABDAD6C7F3747799A X-Mailru-Sender: C5364AD02485212F3ACDC11E67D8491747533F75B4D7E0293DF07BD882ADF97B069BFC61DABEEB110841D3AAAB1726C63DDE9B364B0DF289264D2CD8C2503E8C22A194DADEED8EEDCA01A23BA9CD1BE7ED14614B50AE0675 X-Mras: OK X-Mras: OK Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/03/2018 11:10 AM, Maxime Ripard wrote: > On Thu, Mar 29, 2018 at 09:59:03PM +0300, Sergey Suloev wrote: >> There is no need to handle 3/4 empty/full interrupts as the maximum >> supported transfer length in PIO mode is 64 bytes for sun4i-family >> SoCs. > That assumes that you'll be able to treat the FIFO full interrupt and > drain the FIFO before we have the next byte coming in. This would > require a real time system, and we're not in one of them. > > Maxime > AFAIK in SPI protocol we send and receive at the same time. As soon as the transfer length is <= FIFO depth then it means that at the moment we get TC interrupt all data for this transfer sent/received already. Is your point here that draining FIFO might be a long operation and we can lose next portion of data ?