MMC core stack and blk layer can do some recovery if mmc device runs into broken state for any reasons. So we implement it for DesignWare MMC host controller. >From Synopsys DesignWare Cores Mobile Storage Host Databook (Section 7.4.4), we get the details: 1. Program CMD12 to end any transfer in process. 2. Wait for DTO, even if no response is sent back by the card. 3. Set the following resets: Software reset – BMOD[0] for IDMAC only DMA reset– CTRL[2] FIFO reset – CTRL[1] bits 4. Program the CARD_RESET register with a value of 0 for the bit corresponding to the card number; This can be done at any time when the card is connected to the controller. This programming asserts the RST_n signal and resets the card. 5. Wait for minimum of 1 μs or cclk_in period, which ever is greater 6. After a minimum of 1 μs, the application should program a value of 0 into the CARD_RESET register for the bit corresponding to the card number. This de-asserts the RST_n signal and takes the card out of reset. 7. The application can program a new CMD only after a minimum of 200 us after the de-assertion of the RST_n signal, as per the MMC 4.41 standard. HW reset producer will be call in mmc_init_card before mmc_go_idle. At that time，dw mmc hasn't update clk for itself, so CMD12 is inappropriate and unnecessary. Moreover, if mmc device runs into broken states, DRTO or RTO generated by previous cmd w/ data will make mmc core issue stop already. Then it will retry again and again, issue stop and card status again until the cmd's retry number decrease to zero. That will finally trigger HW reset producer if we declare MMC_CAP_HW_RESET. So there's no need to do step 1 and 2 for the reasons we mentioned above. This implementation can be easily tested by cutting off->On vmmc while doing data accessing in background to simulate that case. And dw_mmc can generate timeout interrupt and make mmc core trigger hw reset producer before re-init mmc card to recover itself. This patchset do following things: - add hw reset for dw_mmc - implement specific hw_reset extention Shawn Lin (2): mmc: dw_mmc: add hw_reset support mmc: dw_mmc: add hw_reset extension hook drivers/mmc/host/dw_mmc.c | 33 +++++++++++++++++++++++++++++++++ drivers/mmc/host/dw_mmc.h | 6 ++++++ 2 files changed, 39 insertions(+) -- 2.3.7 -- 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
