From mboxrd@z Thu Jan 1 00:00:00 1970 From: Valdis.Kletnieks@vt.edu Subject: Re: [PATCH 01/16] hpsa: do readl after writel in main i/o path to ensure commands don't get lost. Date: Wed, 04 May 2011 13:28:21 -0400 Message-ID: <10639.1304530101@localhost> References: <20110503195750.5478.54853.stgit@beardog.cce.hp.com> <20110503195849.5478.13229.stgit@beardog.cce.hp.com> <4DC13566.5070203@redhat.com> <20110504125212.GC5997@beardog.cce.hp.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1304530101_7352P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Your message of "Wed, 04 May 2011 07:52:12 CDT." <20110504125212.GC5997@beardog.cce.hp.com> Sender: linux-kernel-owner@vger.kernel.org To: scameron@beardog.cce.hp.com Cc: Tomas Henzl , james.bottomley@hansenpartnership.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, smcameron@yahoo.com, akpm@linux-foundation.org, mikem@beardog.cce.hp.com List-Id: linux-scsi@vger.kernel.org --==_Exmh_1304530101_7352P Content-Type: text/plain; charset=us-ascii On Wed, 04 May 2011 07:52:12 CDT, scameron@beardog.cce.hp.com said: > On Wed, May 04, 2011 at 01:15:50PM +0200, Tomas Henzl wrote: > > On 05/03/2011 09:58 PM, Stephen M. Cameron wrote: > > > From: Stephen M. Cameron > > > dev_dbg(&h->pdev->dev, "Sending %x, tag = %x\n", c->busaddr, > > > c->Header.Tag.lower); > > > writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET); > > > + (void) readl(h->vaddr + SA5_REQUEST_PORT_OFFSET); > I just put it there to make it clear that it ignoring the return of readl is > done intentionally, not accidentally. If this goes against some coding convention, > whatever, I'm not super attached to the (void), but I did put it there on purpose, > and would have done it in cciss as well, had I thought of it at the time. This probably needs a comment like /* don't care - dummy read just to force write posting to chipset */ or similar. I'm assuming it's just functioning as a barrier-type flush of some sort? --==_Exmh_1304530101_7352P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFNwYy1cC3lWbTT17ARAtBTAJ99nLBal+gVKChT+db9zUyukiTruQCePk/d zfMU7pRV2aHY12MlQIiuoL8= =qqQi -----END PGP SIGNATURE----- --==_Exmh_1304530101_7352P--