From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: About devm_ioremap_resource() Date: Wed, 3 Feb 2016 17:16:12 -0800 Message-ID: <20160204011612.GA6357@intel.com> References: <20160203225519.GA8647@intel.com> <20160204003108.GA26123@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20160204003108.GA26123-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Jason Gunthorpe Cc: linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: tpmdd-devel@lists.sourceforge.net On Wed, Feb 03, 2016 at 05:31:08PM -0700, Jason Gunthorpe wrote: > On Wed, Feb 03, 2016 at 02:55:19PM -0800, Jarkko Sakkinen wrote: > > Hi > > > > I have couple of concerns with tpm_crb changes made for 4.5: > > > > * I used devm_ioremap_nocache() to disable WB. This does not > > matter when one has ACPI start as it goes through SMM and caches are > > flushed. It might be a problem with a CRB start only TPM device. How does > > devm_ioremap_resource address this? > > ioremap_nocache and ioremap() are the same thing, the former is just > more descriptive. > > devm_ioremap_resource calls ioremap which does ioremap_nocache. > > Resources are assumed to be memory mapped registers, and are always > handled appropriately. > > > * I'm a bit puzzled with that function. Why there exists ioremaps that > > do not add stuff to a resource tree and those that do? Maybe you have > > a deeper understanding in this area could enlighten me since you did > > the commit. > > The resource tree and mapping are different things, not all drivers > can use the resource tree all the time, but certainly the majority of > drivers should be using it, hence the devm helper to do both. > > When you see a ioremap without resource handling in a driver it is > probably a mistake, and if it isn't, IMHO there should be a comment > discussing why this driver cannot lock the resource region. Thank you for clearing these out! I have nothing to add here. The reason for two interfaces was what I expected... > Jason /Jarkko ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140