From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: Re: [PATCH 13/18] ide: use ->tf_load in SELECT_DRIVE() Date: Tue, 17 Feb 2009 18:32:02 +0300 Message-ID: <499AD872.2060605@ru.mvista.com> References: <20080620213323.13202.71450.sendpatchset@localhost.localdomain> <200902162251.49271.bzolnier@gmail.com> <499A0D0B.7070007@ru.mvista.com> <200902171543.21892.bzolnier@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from h155.mvista.com ([63.81.120.155]:26142 "EHLO imap.sh.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750921AbZBQPbl (ORCPT ); Tue, 17 Feb 2009 10:31:41 -0500 In-Reply-To: <200902171543.21892.bzolnier@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Bartlomiej Zolnierkiewicz Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Bartlomiej Zolnierkiewicz wrote: >>>>>>>There should be no functional changes caused by this patch. >>>>>>>Signed-off-by: Bartlomiej Zolnierkiewicz >>>>>>>Index: b/drivers/ide/ide-iops.c >>>>>>>=================================================================== >>>>>>>--- a/drivers/ide/ide-iops.c >>>>>>>+++ b/drivers/ide/ide-iops.c >>>>>>>@@ -88,11 +88,15 @@ void SELECT_DRIVE (ide_drive_t *drive) >>>>>>> { >>>>>>> ide_hwif_t *hwif = drive->hwif; >>>>>>> const struct ide_port_ops *port_ops = hwif->port_ops; >>>>>>>+ ide_task_t task; >>>>>>> >>>>>>> if (port_ops && port_ops->selectproc) >>>>>>> port_ops->selectproc(drive); >>>>>>> >>>>>>>- hwif->OUTB(drive->select.all, hwif->io_ports.device_addr); >>>>>>>+ memset(&task, 0, sizeof(task)); >>>>>>>+ task.tf_flags = IDE_TFLAG_OUT_DEVICE; >>>>>>>+ >>>>>>>+ drive->hwif->tf_load(drive, &task); >>>>>> This actually doesn't seem like a bright idea to me, considering >>>>>>that this gets called when starting every request. How will you look >>>>>>at me adding the transport method for writing this register? :-) >>>Please check profiles first -- it might not be worth it. [1] >>>>>Convert SELECT_DRIVE() to use ->tf_load instead of ->OUTB. >>>>> OTOH, adding such a "backdoor" to the taskfile doesn't seem very >>>>>consistent... well, I'm not excited about the whole idea conversion to >>>>>tf_{load|read}() -- it's not clear what exactly this bought us. >>>This was explained some months ago already, so just to recall -- it was >>>a part of a bigger work removing duplicated code and allowing abstraction >>>of the ATA logic. >>>Anyway this is not set in a stone so if you have proposal of a better >>>approach please come forward with it. >> Er... I think that the previous IN()/OUT() methods were better. Note >>that we ended up using the local version of them in the dafault >>ide_tf_{load}read}() anyway -- as Alan has pointed out it might be worth > During ide_tf_{load,read}() addition I was a bit too optimistic about > the possibility of the quick io{read,write}* conversion later... >>splitting those into I/O and memory space versions... although given >>general slowness of the I/O accesses, this is probably not going to win >>much speed-wise. > Maybe it would be worth to add ->tf_{inb,outb} to struct ide_tp_ops > and convert default tp_ops to use them... OTOH we should reinvestigate > the io{read,write}*() way first (maybe things have improved there)... Yes, let's not be hasty here... >>>> We at least could have saved on memset() -- tf_load() method ignores >>>>fields other than tf_flags anyway... >>>Unless it is huge performance win (unlikely) this is not a good idea as it would be a maintainance nightmare. >>>->tf_load does only use cmd->tf_flags today but it might change one day >>>and nobody will remember to audit all users that they pass a valid cmd... >> It's just quite unbearable to see (especially for a long time >>assembly coder) how a single register write is turning into *that*. >>So, it still seems worth risking... :-) > I see your point here. If SELECT_DRIVE() is performance sensitive we > may just add another struct ide_tp_ops method for it... Or we may finally teach selectproc() to also do that, turning it into analog of libata's dev_select() method. > Thanks, > Bart MBR, Sergei