On 2 December 2014 at 12:53, Asutosh Das <asutoshd@xxxxxxxxxxxxxx> wrote: > In this patch series, we propose a method to add support for > Command Queueing(CQ) feature added to eMMC-5.1 specification. > This feature includes new commands for issuing tasks to the > device and orders the execution of tasks to the device. It > also has task management functions. > > The initialization of CQ is decided based on the underlying > driver capability and the capability advertised by the card > through ext_csd. > > We have selectively adopted the scsi design of pulling in > requests from kernel block layer. > > In order to support queueing of multiple requests, we have > added a new issue function to mmc-queue. This selectively > pulls the requests and prepares and issues it to the underlying > driver. We have used the inherent tagging mechanism of kernel > block layer to keep track and map tags to the slots of underlying > driver. The current design doesn't block for the request to > complete. We have separated the issuing and completion path > of the request and tracking is done using the tag assigned to > the request. > > We have introduced a number of APIs to mmc block layer to > facilitate servicing of requests. > > The completion of requests is handled in a softirq registered > with the kernel block layer during initialization. The error > handling however would be done using a workqueue and is under > development. > > We have separated the legacy eMMC code from CQ code, so as to > make it more manageable. > > A new layer has been introduced to serve the CQ compliant drivers. > This layer (cq_hci) has all the standard functionality implemented. > It also has necessary hooks for convenience of platform drivers. Hi Asutosh, Thanks for posting this patchset! It's an interesting feature eMMC 5.1 has adopted. I also hope to get some input from several other reviewers around this patchset. Let me start by give some generic initial feedback: 1) I think we have earlier merged/reviewed code for new eMMC/SD features, without demanding excellent code quality. I will not let that happen again, just so you guys know. Nothing said about this patchset as such! 2) Earlier we have accepted to add new features without these being properly validated on HW. The result is that we might have dead code, since it's hard to tell whether is actually used and thus working. I will demand all features to be tested on HW before I merge them. I guess that won't be an issue here, right? 3) Adding new big features shall be thoroughly justified. In this case, showed by improved performance. Such performance statistics shall in this case have the reference from a host driver that supports the asynchronous request mechanism. So, if your host driver doesn't support that currently, that's the first thing you should be looking into. I will get back to review the actual patches as soon as I can. Kind regards Uffe -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
