From mboxrd@z Thu Jan 1 00:00:00 1970 From: Finn Thain Subject: Re: [PATCH] scsi:NCR5380: remove same check condition in NCR5380_select Date: Fri, 3 Aug 2018 16:04:33 +1000 (AEST) Message-ID: References: <1533179408-20631-1-git-send-email-zhongjiang@huawei.com> <5B627E71.5020600@huawei.com> <928ae07a-8c4a-05fc-16af-48fb6e9c341d@gmail.com> <6e28be9a-b601-17e2-4a04-9635925e5958@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <6e28be9a-b601-17e2-4a04-9635925e5958@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Michael Schmitz Cc: zhong jiang , Bart Van Assche , "jejb@linux.vnet.ibm.com" , "martin.petersen@oracle.com" , "andy.shevchenko@gmail.com" , "linux-scsi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "john.garry@huawei.com" List-Id: linux-scsi@vger.kernel.org On Fri, 3 Aug 2018, Michael Schmitz wrote: > > > Finn - does the ICR_ARBITRATION_LOST bit have to be cleared by a > > > write to the mode register? > > > > > > > Something like that: the write to the mode register does clear the > > ICR_ARBITRATION_LOST bit, because it clears the MR_ARBITRATE bit. > > Yes, but is that the only way the bit can get cleared? [...] Short of a reset, yes. > > > > In that case, the first load would have been redundant and can be > > > omitted without changing driver behaviour? > > > > This code is a faithful rendition of the arbitration flow chart in the > > datasheet, so even if you are right, I wouldn't want to change the > > code. > > I think that's a pretty clear hint that the 'arbitration lost' condition > isn't latched. [...] It's not a hint. It's just an algorithm with fewer assumptions than the one you proposed. As for latching, the datasheet is pretty clear on that. Writing MR_BASE to the mode register clears the ICR_ARBITRATION_LOST bit. As in, if ((NCR5380_read(INITIATOR_COMMAND_REG) & ICR_ARBITRATION_LOST) || (NCR5380_read(CURRENT_SCSI_DATA_REG) & hostdata->id_higher_mask) || (NCR5380_read(INITIATOR_COMMAND_REG) & ICR_ARBITRATION_LOST)) { NCR5380_write(MODE_REG, MR_BASE); --