From mboxrd@z Thu Jan 1 00:00:00 1970 From: Per Forlin Subject: Re: [PATCH v2 01/12] mmc: add none blocking mmc request function Date: Tue, 26 Apr 2011 16:22:12 +0200 Message-ID: References: <1302116833-24540-1-git-send-email-per.forlin@linaro.org> <1302116833-24540-2-git-send-email-per.forlin@linaro.org> <4DA81F42.3070208@csr.com> <4DB6C89F.10903@csr.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <4DB6C89F.10903-kQvG35nSl+M@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linaro-dev-bounces-cunTk1MwBs8s++Sfvej+rw@public.gmane.org Errors-To: linaro-dev-bounces-cunTk1MwBs8s++Sfvej+rw@public.gmane.org To: David Vrabel Cc: linaro-dev-cunTk1MwBs8s++Sfvej+rw@public.gmane.org, linux-mmc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-mmc@vger.kernel.org On 26 April 2011 15:29, David Vrabel wrote: > On 20/04/11 08:17, Per Forlin wrote: >> >>> Using a MMC request queue has other benefits -- it allows multiple users >>> without having to claim/release the host. =A0This would be useful for >>> (especially multi-function) SDIO. >> >> You mean claim and release would be done only within the mmc core. The >> timed saved here would equal the time it takes to release and claim >> the host. >> Claim and release can also be used for power management to indicate if >> any client is using the host, if not the power can be switched off. > > Isn't there a separate runtime power management API that different from > claim/release? > I misunderstood. I thought you meant that the claim() and release() were not needed if having an internal request queue in core.c. Please discard my comment. >> I just want to make sure I understand the multi-function SDIO case, I >> haven't done any work with SDIO. >> Can the SDIO functions compete over the same claim_host at the same time? >> Example: if function 1 claims the host, function 2 and function 3 also >> want to claim the host but have to wait for function 1 to release the >> host. > > This is the case. =A0 Each function driver has to claim exclusive access > to the host. > >> What is the extra benefit of having the internal request queue for >> multi function SDIO? > > It reduces the delays between commands if multiple drivers are sending > commands. =A0I estimated performance improvements with 2-3% from just > removing the need to claim/release in one particular SDIO function > driver. =A0Performance improvements for multi-function cards would be a > bit more (5% perhaps?). > Your estimates are promising. > The more important benefit is the simplification of the API. I agree. I will make a prototype for this. I don't think I will be able to find time for this until middle of May. I let know you when I have patches. > > David Thanks, Per