Re: eMMC boot problem: switch to bus width 8 ddr failed

[Clemens Gruber <clemens.gruber@pqgruber.com>]

On Fri, Jan 06, 2017 at 10:33:49AM +0800, Shawn Lin wrote:
> On 2017/1/6 8:41, Clemens Gruber wrote:
> > Hi,
> > 
> > with the current mainline 4.10-rc2 kernel, I can no longer boot from
> > the eMMC on my i.MX6Q board.
> > 
> > Details:
> > The eMMC is a Micron MTFC4GACAJCN-1M WT but as the i.MX6Q only supports
> > eMMC 4.41 features and we did not implement voltage switching from 3.3V
> > to 1.8V or lower, I did add no-1-8-v; (but none of the mmc-ddr or mmc-hs
> > options) to the device tree. The bus-width is 8.
> > 
> > With 4.9 the board booted fine, now with the current mainline 4.10 tree,
> > I get the following (repeating) errors at boot:
> > 
> > [    4.326834] Waiting for root device /dev/mmcblk0p2...
> > [   14.563861] mmc0: Timeout waiting for hardware cmd interrupt.
> > [   14.569619] sdhci: =========== REGISTER DUMP (mmc0)===========
> > [   14.575461] sdhci: Sys addr: 0x4e726000 | Version:  0x00000002
> > [   14.581300] sdhci: Blk size: 0x00000200 | Blk cnt:  0x00000001
> > [   14.587140] sdhci: Argument: 0x00010000 | Trn mode: 0x00000013
> > [   14.592979] sdhci: Present:  0x01fd8009 | Host ctl: 0x00000031
> > [   14.598816] sdhci: Power:    0x00000002 | Blk gap:  0x00000080
> > [   14.604654] sdhci: Wake-up:  0x00000008 | Clock:    0x0000001f
> > [   14.610493] sdhci: Timeout:  0x0000008f | Int stat: 0x00000000
> > [   14.616332] sdhci: Int enab: 0x107f100b | Sig enab: 0x107f100b
> > [   14.622168] sdhci: AC12 err: 0x00000000 | Slot int: 0x00000003
> > [   14.628007] sdhci: Caps:     0x07eb0000 | Caps_1:   0x0000a007
> > [   14.633845] sdhci: Cmd:      0x00000d1a | Max curr: 0x00ffffff
> 
> it shows you always fail to get resp of sending status within the
> expected period of time.
> 
> 
> > [   14.639682] sdhci: Host ctl2: 0x00000000
> > [   14.643611] sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x4e6f7208
> > [   14.649447] sdhci: ===========================================
> > 
> > This repeats a few times, then more information is shown at the bottom:
> > 
> > [   86.893859] mmc0: Timeout waiting for hardware cmd interrupt.
> > [   86.899615] sdhci: =========== REGISTER DUMP (mmc0)===========
> > [   86.905453] sdhci: Sys addr: 0x00000000 | Version:  0x00000002
> > [   86.911291] sdhci: Blk size: 0x00000200 | Blk cnt:  0x00000001
> > [   86.917129] sdhci: Argument: 0x00010000 | Trn mode: 0x00000013
> > [   86.922967] sdhci: Present:  0x01fd8009 | Host ctl: 0x00000031
> > [   86.928804] sdhci: Power:    0x00000002 | Blk gap:  0x00000080
> > [   86.934642] sdhci: Wake-up:  0x00000008 | Clock:    0x0000001f
> > [   86.940479] sdhci: Timeout:  0x0000008f | Int stat: 0x00000000
> > [   86.946316] sdhci: Int enab: 0x107f100b | Sig enab: 0x107f100b
> > [   86.952154] sdhci: AC12 err: 0x00000000 | Slot int: 0x00000003
> > [   86.957992] sdhci: Caps:     0x07eb0000 | Caps_1:   0x0000a007
> > [   86.963830] sdhci: Cmd:      0x00000d1a | Max curr: 0x00ffffff
> > [   86.969668] sdhci: Host ctl2: 0x00000000
> > [   86.973596] sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x00000000
> > [   86.979433] sdhci: ===========================================
> > [   86.986356] mmc0: switch to bus width 8 ddr failed
> > [   86.991163] mmc0: error -110 whilst initialising MMC card
> > [   97.773859] mmc0: Timeout waiting for hardware cmd interrupt.
> > 
> > --
> > 
> > After looking through the latest commits to mmc/core, I found the
> > culprit:
> > Commit e173f8911f091fa50ccf8cc1fa316dd5569bc470 ("mmc: core: Update
> > CMD13 polling policy when switch to HS DDR mode")
> > 
> > Reverting it fixes the problem. But I am unsure if that's the right
> > course of action?
> > 
> > Feel free to send me patches for testing!
> 
> By looking the changes itself, it should be good from the view of spec.
> Maybe you could try the patch below, but don't beat me if that doesn't
> help at all. :)
> 
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1074,7 +1074,7 @@ static int mmc_select_hs_ddr(struct mmc_card *card)
>                            EXT_CSD_BUS_WIDTH,
>                            ext_csd_bits,
>                            card->ext_csd.generic_cmd6_time,
> -                          MMC_TIMING_MMC_DDR52,
> +                          0,
>                            true, true, true);
>         if (err) {
>                 pr_err("%s: switch to bus width %d ddr failed\n",
> @@ -1118,6 +1118,9 @@ static int mmc_select_hs_ddr(struct mmc_card *card)
>         if (err)
>                 err = __mmc_set_signal_voltage(host,
> MMC_SIGNAL_VOLTAGE_330);
> 
> +       if (!err)
> +               mmc_set_timing(host, MMC_TIMING_MMC_DDR52);
> +
> 
> 

Hi,

thank you. This patch solves the problem! :)

Tested-by: Clemens Gruber <clemens.gruber@pqgruber.com>

Regards,
Clemens