On Monday 26 January 2015 22:04:59 Pali Rohár wrote: > Hello, > > for unknown reason kernel in qemu n900 machine is not able to > detect internal eMMC memory. External SD card is detected without > problem. > > If I apply this one-line patch eMMC in qemu start working: > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > index 9584bff..0d4461c 100644 > --- a/drivers/mmc/core/core.c > +++ b/drivers/mmc/core/core.c > @@ -2337,6 +2337,9 @@ static int mmc_rescan_try_freq( > return 0; > if (!mmc_attach_sd(host)) > return 0; > + > + mmc_go_idle(host); > + > if (!mmc_attach_mmc(host)) > return 0; > > I played with mmc and qemu n900 a bit and also this simple patch > (without first) fix problem (that mmc is not detected by kernel): > > diff --git a/drivers/mmc/core/mmc_ops.c > b/drivers/mmc/core/mmc_ops.c > index 3b044c5..0c93a2c 100644 > --- a/drivers/mmc/core/mmc_ops.c > +++ b/drivers/mmc/core/mmc_ops.c > @@ -157,6 +157,10 @@ int mmc_send_op_cond( > > BUG_ON(!host); > > + /* reset mmc before calling op_cond */ > + memset(&cmd, 0, sizeof(struct mmc_command)); > + mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES); > + > cmd.opcode = MMC_SEND_OP_COND; > cmd.arg = mmc_host_is_spi(host) ? 0 : ocr; > cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R3 | MMC_CMD_BCR; > > > I have no idea where is problem. I also do not understand mmc > kernel code, but second patch I have on my HDD since 2.6.37. > > Can somebody with knowledge of mmc subsystem look at this > problem? Why any of these two patches fix problem when mmc is not > detected by kernel in qemu (machine n900)? Detection of mmc fails > because function mmc_send_op_cond() without one of above patches > fails. I will bring this tread to front again as mmc without one of provided patches does not work with 4.4-rc6 kernel in N900 qemu. -- Pali Rohár pali.rohar@xxxxxxxxx
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