Hi Subhash, > -----Original Message----- > From: Subhash Jadavani [mailto:subhashj@xxxxxxxxxxxxxx] > Sent: Saturday, April 16, 2011 11:47 AM > To: 'Andrei Warkentin'; Nath, Arindam; linux-mmc@xxxxxxxxxxxxxxx > Subject: RE: [PATCH v3 01/12] mmc: sdhci: add support for auto CMD23 > > > -----Original Message----- > > From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc- > > owner@xxxxxxxxxxxxxxx] On Behalf Of Andrei Warkentin > > Sent: Saturday, April 16, 2011 1:34 AM > > To: Nath, Arindam; linux-mmc@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH v3 01/12] mmc: sdhci: add support for auto CMD23 > > > > +linux-mmc > > > > On Fri, Apr 15, 2011 at 3:03 PM, Andrei Warkentin > > <andreiw@xxxxxxxxxxxx> wrote: > > > On Fri, Apr 15, 2011 at 1:57 PM, Andrei Warkentin > > <andreiw@xxxxxxxxxxxx> wrote: > > >> Hi Arindam, > > >> > > >> On Fri, Apr 15, 2011 at 12:34 PM, Nath, Arindam > > <Arindam.Nath@xxxxxxx> wrote: > > >>> Hi Andrei, > > >> > > >>>> > > >>>> I've recently posted changes relating to CMD23 support in block > > layer. > > >>>> Effectively, in order to support hosts with and without > > >>>> Auto-CMD23 (and with proper error handling) there is a new > > >>>> MMC_CAP_CMD23 for > > the > > >>>> host, and a new field "mmc_command sbc" inside the mmc_request. > > >>>> > > >>>> I also have a patch enabling CMD23 use with an SDHCI host (< > > 3.00). > > >>>> > > >>>> Could you be so kind as to rebase this patch on top of that? > > You're > > >>>> doing a lot of things here that you really shouldn't be (like > > >>>> enforcing policy on what gets sent to cards, knowing what's > > connected > > >>>> to the host, conflicting with reliable writes code if Auto-CMD23 > > was > > >>>> enabled for MMCs, not supporting MMCs which always have > > >>>> SET_BLOCK_COUNT). > > >>> > > >>> Our Host Controller is complaint to the Host Controller Spec > > >>> v3.00, > > and since Auto CMD23 is a feature added to the HC, I thought it would > > be better to make this feature part of sdhci and not the core/block > > layer. > > >>> > > >>> But in case you want Auto CMD23 to be implemented in a different > > way, it would rather be great if you help me implement in your own > > way, and then probably based on community suggestions, we can keep > > either of the patch. > > >> > > >> Let me clarify: > > >> > > >> 1) Sending CMD23 on multiblock transfers is not a an SDHCI > specific > > >> feature. It's a feature of MMC cards and SD cards operating at > > UHS104 > > >> or greater. > > >> 2) CMD23-bounded multi block writes are a generic problem already > - > > >> eMMC reliable writes, for example. > > >> 3) CMD23 is not bound to any specific controller - so having > > >> generic code to allow execution of CMD23 will speed up transfers > > >> (and enable certain features) on any host. > > These are the same point I had discussed earlier with Arindam. Please > check the attached mails. > > Yes, I would also agree with Andrei that all generic code related to > CMD23 handling should be in core/block layer. Internally host > controller driver can handle CMD23 differently as not all host > controller support AUTO-CMD23. Please keep in mind that my patch _only_ adds support for Auto CMD23, and not CMD23. CMD23 support can be made part of block layer, but Auto CMD23 is a feature as per the Host Controller Spec v3.00. So my patch takes care of the second case. Thanks, Arindam > > > >> 4) Auto-CMD is a specific SDHCI enhancement, meant to reduce > > overhead > > >> of sending CMD23. > > >> 5) Host controller has to be aware of CMD23 sending, because on an > > >> error STOP has to be sent, and without error, no STOP has to be > > sent. > > >> > > >> You are in a unique position where you have functional SDHCI 3.0 > > >> hardware and are able to test Auto-CMD23. Please look at the patch > > set > > >> I sent - it should be trivial to extend current SDHCI patch to use > > >> Auto-CMD23 when possible instead of sending mmc_request->sbc. > > >> Basically, I have a generic improvement that affects all host > > >> controllers. Auto-CMD23 is an optimization of that for SDHCI 3.0. > > >> > > >> Your current patch to enable Auto-CMD23 is not useful as far as > > >> non- > > SD > > >> cards are concerned and you push way to much policy and > > >> non-host-related complexity into it. > > >> > > >> Thanks, > > >> A > > >> > > > > > > More clarification: > > > > > > The block layer patch may change slightly > (whitelisting/blacklisting > > > certain MMC devices for using CMD23 for multiblock transfers), but > > the > > > changes to mmc_request and SDHCI are not. So feel free to rebase it > > > without waiting for anything. If you need help, I will gladly help > > > you, but keep in mind I don't have SDHCI 3.0 hardware around. > > > > > > Thanks, > > > A > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-mmc" > > in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo > > info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
