RE: [RFC PATCH 0/5]mmc: Soft Command queue implementation for eMMC5.1 device

Alex Lemberg
2015-02-11T14:14:47Z

Hi Chuanxiao,

I have a question from the review of your SW CMDQ driver code.

>From the eMMC5.1 spec, the "ready for execution" for each task should be cleared by the device only when the last data block has been fully transferred over the eMMC bus.

However, from the code, I can recognize the following suspected case:

1. Host sends CMD44/45 commands for TID#0
2. Host sends CMD13 (QSR) -> returned TID#0 ready for execution
3. Host sends CMD46 for TID#0
4. During the data transfer, host may send CMD13 (QSR) -> returned TID#0 ready for execution (which is true since data is still in transfer)
5. Host sends CMD46 for TID#0 (same as sent in bullet#3) - which is a problem.

Please advise if my assumption above is correct.

Thanks,
Alex

> -----Original Message-----
> From: linux-mmc-owner@vger.kernel.org [mailto:linux-mmc-
> owner@vger.kernel.org] On Behalf Of Chuanxiao Dong
> Sent: Friday, December 19, 2014 10:05 AM
> To: linux-mmc@vger.kernel.org
> Subject: [RFC PATCH 0/5]mmc: Soft Command queue implementation for
> eMMC5.1 device
>
> Hello,
>
> Seems community already have some implementation for the eMMC5.1 device
> command queue feature, but that require the eMMC host controller to support
> CMDQ. In my platform, I don't have this kind of eMMC host controller but I
> have a Samsung eMMC5.1 device which can support the Command queue.
>
> With this limitation, I have to let eMMC host controller to manually send the
> CMD44/45/13/46/47. So in this way, more commands are needed for an I/O
> request, more interrupts/schedule are needed in driver.
>
> Even this way have some more software overhead, but it can still use the
> eMMC5.1 device Command queue feature. After test with the iozone
> command:
> "iozone -zec -t 4 -i0 -i2 -F iozonefile1 iozonefile2 iozonefile3 iozonefile4 -+n -I -r
> 4k -s 500m -O -R -+r -+D" to test random performance, I saw a performance
> improvment for random read on my eMMC5.1 device:
>
> Random read
> SW CMDQ: 5544.6
> Normal Read: 3993.05
>
> So I want to send this serial patches as RFC patch for reviewing
>
>
> Chuanxiao Dong (5):
> mmc: replace sbc to precmd and add postcmd
> mmc: host: add runtime PM for host class dev
> mmc: queue: change mqrq_cur and mqrq_pre to mq qdepth
> mmc: core: add support for CMDQ feature in MMC Core stack
> mmc: sdhci: add SW CMDQ support for CHT SDHCI host
>
> drivers/mmc/card/block.c | 538
> ++++++++++++++++++++++++++++++++++++++---
> drivers/mmc/card/queue.c | 213 ++++++++--------
> drivers/mmc/card/queue.h | 14 +-
> drivers/mmc/core/core.c | 78 +++++-
> drivers/mmc/core/host.c | 14 ++
> drivers/mmc/core/mmc.c | 43 +++-
> drivers/mmc/host/dw_mmc.c | 8 +-
> drivers/mmc/host/mmci.c | 14 +-
> drivers/mmc/host/omap_hsmmc.c | 18 +-
> drivers/mmc/host/sdhci-acpi.c | 1 -
> drivers/mmc/host/sdhci-pci.c | 1 -
> drivers/mmc/host/sdhci.c | 137 +++++++++--
> include/linux/mmc/card.h | 3 +
> include/linux/mmc/core.h | 5 +-
> include/linux/mmc/host.h | 5 +
> include/linux/mmc/mmc.h | 21 ++
> include/linux/mmc/pm.h | 1 +
> include/linux/mmc/sdhci.h | 1 +
> 18 files changed, 909 insertions(+), 206 deletions(-)
>
> --
> 1.7.10.4
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