Subject: [PATCH 3/3] mmc: dw_mmc: Support voltage changes

From: [email-masked] (Seungwon Jeon)
Date: Tue, 08 Jul 2014 18:56:48 +0900

On Tue, July 08, 2014,Yuvaraj Kumar wrote:
> On Mon, Jul 7, 2014 at 10:53 AM, Seungwon Jeon <[email-masked]> wrote:
> > On Fri, July 04, 2014, Seungwon Jeon wrote:
> >> On Tue, July 01, 2014. Yuvaraj Kumar wrote:
> >> > On Fri, Jun 27, 2014 at 4:48 PM, Seungwon Jeon <[email-masked]> wrote:
> >> > > Hi Yuvaraj,
> >> > >
> >> > > On Fri, June 27, 2014, Yuvaraj Kumar wrote:
> >> > >> On Thu, Jun 26, 2014 at 10:20 PM, Doug Anderson <[email-masked]> wrote:
> >> > >> > Seungwon,
> >> > >> >
> >> > >> > On Thu, Jun 26, 2014 at 3:41 AM, Seungwon Jeon <[email-masked]> wrote:
> >> > >> >> On Thu, June 26, 2014, Doug Anderson wrote:
> >> > >> >>> Seungwon,
> >> > >> >>>
> >> > >> >>> On Wed, Jun 25, 2014 at 6:08 AM, Seungwon Jeon <[email-masked]> wrote:
> >> > >> >>> > On Mon, June 23, 2014, Yuvaraj Kumar C D wrote:
> >> > >> >>> >> Subject: [PATCH 3/3] mmc: dw_mmc: Support voltage changes
> >> > >> >>> >>
> >> > >> >>> >> From: Doug Anderson <[email-masked]>
> >> > >> >>> >>
> >> > >> >>> >> For UHS cards we need the ability to switch voltages from 3.3V to
> >> > >> >>> >> 1.8V.  Add support to the dw_mmc driver to handle this.  Note that
> >> > >> >>> >> dw_mmc needs a little bit of extra code since the interface needs a
> >> > >> >>> >> special bit programmed to the CMD register while CMD11 is progressing.
> >> > >> >>> >> This means adding a few extra states to the state machine to track.
> >> > >> >>> >
> >> > >> >>> > Overall new additional states makes it complicated.
> >> > >> >>> > Can we do that in other way?
> >> > >> >>>
> >> > >> >>> That was the best I was able to figure out when I thought this
> >> > >> >>> through.  If you have ideas for doing it another way I'd imagine that
> >> > >> >>> Yuvaraj would be happy to take your feedback.
> >> > >> >> Let's clean up SDMMC_CMD_VOLT_SWITCH.
> >> > >> >> In turn, we may remove state-handling simply.
> >> > >> >>
> >> > >> >>>
> >> > >> >>>
> >> > >> >>> >> Signed-off-by: Doug Anderson <[email-masked]>
> >> > >> >>> >> Signed-off-by: Yuvaraj Kumar C D <[email-masked]>
> >> > >> >>> >>
> >> > >> >>> >> ---
> >> > >> >>> >>  drivers/mmc/host/dw_mmc.c  |  145 +++++++++++++++++++++++++++++++++++++++++---
> >> > >> >>> >>  drivers/mmc/host/dw_mmc.h  |    5 +-
> >> > >> >>> >>  include/linux/mmc/dw_mmc.h |    2 +
> >> > >> >>> >>  3 files changed, 142 insertions(+), 10 deletions(-)
> >> > >> >>> >>
> >> > >> >>> >> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> >> > >> >>> >> index e034bce..38eb548 100644
> >> > >> >>> >> --- a/drivers/mmc/host/dw_mmc.c
> >> > >> >>> >> +++ b/drivers/mmc/host/dw_mmc.c
> >> > >> >>> >> @@ -29,6 +29,7 @@
> >> > >> >>> >>  #include <linux/irq.h>
> >> > >> >>> >>  #include <linux/mmc/host.h>
> >> > >> >>> >>  #include <linux/mmc/mmc.h>
> >> > >> >>> >> +#include <linux/mmc/sd.h>
> >> > >> >>> >>  #include <linux/mmc/sdio.h>
> >> > >> >>> >>  #include <linux/mmc/dw_mmc.h>
> >> > >> >>> >>  #include <linux/bitops.h>
> >> > >> >>> >> @@ -235,10 +236,13 @@ err:
> >> > >> >>> >>  }
> >> > >> >>> >>  #endif /* defined(CONFIG_DEBUG_FS) */
> >> > >> >>> >>
> >> > >> >>> >> +static void mci_send_cmd(struct dw_mci_slot *slot, u32 cmd, u32 arg);
> >> > >> >>> >> +
> >> > >> >>> >>  static u32 dw_mci_prepare_command(struct mmc_host *mmc, struct mmc_command *cmd)
> >> > >> >>> >>  {
> >> > >> >>> >>       struct mmc_data *data;
> >> > >> >>> >>       struct dw_mci_slot *slot = mmc_priv(mmc);
> >> > >> >>> >> +     struct dw_mci *host = slot->host;
> >> > >> >>> >>       const struct dw_mci_drv_data *drv_data = slot->host->drv_data;
> >> > >> >>> >>       u32 cmdr;
> >> > >> >>> >>       cmd->error = -EINPROGRESS;
> >> > >> >>> >> @@ -254,6 +258,32 @@ static u32 dw_mci_prepare_command(struct mmc_host *mmc, struct
> >> > mmc_command
> >> > >> >>> *cmd)
> >> > >> >>> >>       else if (cmd->opcode != MMC_SEND_STATUS && cmd->data)
> >> > >> >>> >>               cmdr |= SDMMC_CMD_PRV_DAT_WAIT;
> >> > >> >>> >>
> >> > >> >>> >> +     if (cmd->opcode == SD_SWITCH_VOLTAGE) {
> >> > >> >>> >> +             u32 clk_en_a;
> >> > >> >>> >> +
> >> > >> >>> >> +             /* Special bit makes CMD11 not die */
> >> > >> >>> >> +             cmdr |= SDMMC_CMD_VOLT_SWITCH;
> >> > >> >>> >> +
> >> > >> >>> >> +             /* Change state to continue to handle CMD11 weirdness */
> >> > >> >>> >> +             WARN_ON(slot->host->state != STATE_SENDING_CMD);
> >> > >> >>> >> +             slot->host->state = STATE_SENDING_CMD11;
> >> > >> >>> >> +
> >> > >> >>> >> +             /*
> >> > >> >>> >> +              * We need to disable clock stop while doing voltage switch
> >> > >> >>> >> +              * according to 7.4.1.2 Voltage Switch Normal Scenario.
> >> > >> >>> >> +              *
> >> > >> >>> >> +              * It's assumed that by the next time the CLKENA is updated
> >> > >> >>> >> +              * (when we set the clock next) that the voltage change will
> >> > >> >>> >> +              * be over, so we don't bother setting any bits to synchronize
> >> > >> >>> >> +              * with dw_mci_setup_bus().
> >> > >> >>> >> +              */
> >> > >> >>> >> +             clk_en_a = mci_readl(host, CLKENA);
> >> > >> >>> >> +             clk_en_a &= ~(SDMMC_CLKEN_LOW_PWR << slot->id);
> >> > >> >>> >> +             mci_writel(host, CLKENA, clk_en_a);
> >> > >> >>> >> +             mci_send_cmd(slot, SDMMC_CMD_UPD_CLK |
> >> > >> >>> >> +                          SDMMC_CMD_PRV_DAT_WAIT, 0);
> >> > >> >>> > dw_mci_disable_low_power() can be used here.
> >> > >> >>>
> >> > >> >>> Ah.  I guess we don't have that locally anymore.  Locally we have variants on:
> >> > >> >> I'm checking on cjb/mmc branch.
> >> > >> >>
> >> > >> >>> * https://patchwork.kernel.org/patch/3070311/
> >> > >> >>> * https://patchwork.kernel.org/patch/3070251/
> >> > >> >>> * https://patchwork.kernel.org/patch/3070221/
> >> > >> >>>
> >> > >> >>> ...which removed that function.  ...but I guess upstream never picked
> >> > >> >>> up those patches, huh?  Looking back it looks like you had some
> >> > >> >>> feedback and it needed another spin but somehow fell off my plate.  :(
> >> > >> >>>
> >> > >> >>> Maybe this is something Yuvaraj would like to pick up?
> >> > >> >> It's long ago. I remember that there is no progress since my last comment.
> >> > >> >> In case of patch "3070221", I want to pick up for next Kernel.
> >> > >> >
> >> > >> > Sounds like Yuvaraj has agreed to look at addressing your comments.  Thanks!
> >> > >> >
> >> > >> >
> >> > >> >>> >> +     }
> >> > >> >>> >> +
> >> > >> >>> >>       if (cmd->flags & MMC_RSP_PRESENT) {
> >> > >> >>> >>               /* We expect a response, so set this bit */
> >> > >> >>> >>               cmdr |= SDMMC_CMD_RESP_EXP;
> >> > >> >>> >> @@ -776,11 +806,15 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool
> >> > force_clkinit)
> >> > >> >>> >>       unsigned int clock = slot->clock;
> >> > >> >>> >>       u32 div;
> >> > >> >>> >>       u32 clk_en_a;
> >> > >> >>> >> +     u32 sdmmc_cmd_bits = SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT;
> >> > >> >>> >> +
> >> > >> >>> >> +     /* We must continue to set bit 28 in CMD until the change is complete */
> >> > >> >>> >> +     if (host->state == STATE_WAITING_CMD11_DONE)
> >> > >> >>> >> +             sdmmc_cmd_bits |= SDMMC_CMD_VOLT_SWITCH;
> >> > >> >>> > I didn't get the reason SDMMC_CMD_VOLT_SWITCH is needed during clock
> update(enable/disable)
> >> > >> >>> > Can you explain it in details?
> >> > >> >>>
> >> > >> >>> Simply put: if I didn't do this then the system hung during voltage
> >> > >> >>> switch.  It was not documented in the version of the IP manual that I
> >> > >> >>> had access to and it took me a bunch of digging / trial and error to
> >> > >> >>> figure this out.  Whatever this bit does internally it's important to
> >> > >> >>> set it while the voltage change is happening.  Note that this need was
> >> > >> >>> the whole reason for adding the extra state to the state machine.
> >> > >> >>>
> >> > >> >>> Perhaps Yuvaraj can try without it and I'd assume he'll report the
> >> > >> >>> same freeze.
> >> > >> >> Clarify the necessity of SDMMC_CMD_VOLT_SWITCH.
> >> > >> >> As far as I experience, we didn't apply this bit for several projects.
> >> > >> >
> >> > >> > I just tried this locally on our ChromeOS 3.8 kernel (which has quite
> >> > >> > a few backports and matches dw_mmc upstream pretty closely).  When I
> >> > >> > take out "sdmmc_cmd_bits |= SDMMC_CMD_VOLT_SWITCH" and bootup it fails
> >> > >> > to bringup WiFi chip.  It prints messages like:
> >> > >> >
> >> > >> > [    4.400842] mmc_host mmc1: Timeout sending command (cmd 0x202000
> >> > >> > arg 0x0 status 0x80202000)
> >> > >> >
> >> > >> > I will let Yuvaraj comment about his testing too.
> >> > >> To make it simple and verify, i have just enabled eMMC and SD channels
> >> > >> on 3.16-rc1 and tested.
> >> > >> Without "sdmmc_cmd_bits |= SDMMC_CMD_VOLT_SWITCH" bootup fails.
> >> > >> [    3.015971] mmc_host mmc1: Timeout sending command (cmd 0x202000
> >> > >> arg 0x0 status 0x80202000)
> >> > >> [    3.530974] mmc_host mmc1: Timeout sending command (cmd 0x202000
> >> > >> arg 0x0 status 0x80202000)
> >> > > Thank you for test.
> >> > > Hmm, it failed during clock update, right?.
> >> > > Can you check HLE interrupt at this time?
> >> > > I'll investigate for this.
> >> > Yes, it failed during clock update.I am dumping the register contents
> >> > just before the dev_err statement.I can observe that 1st timeout does
> >> > not have HLE interrupt.But once we set bit 0 of UHS_REG subsequent
> >> > timeout's have HLE bit set.I am attaching the complete log.
> >>
> >> Before disabling the clocks, we ensure that the card is not busy.(It's from Synopsys's databook)
> >> I guess SDMMC_CMD_VOLT_SWITCH flag seems to affect to avoid this limitation if you have no problem.
> >> But, I met the following log with HEL when I apply and test this patch .
> >>
> >> "mmc_host mmc1: Timeout sending command (cmd 0x202000 arg 0x0 status 0x80202000)"
> >> I need to look into it more deeply.
> > I confirmed that SDMMC_CMD_VOLT_SWITCH is needed during clock-off/on in voltage switching sequence
> > even though there is no description for this in Synopsys's databook.
> > And the above-mentioned message("mmc_host mmc1: Timeout sending command (cmd 0x202000 arg 0x0 status
> 0x80202000)")
> > is happened on mmc_power_cycle(), which should be done because of busy status of DAT[3:0].
> > It indicates clock-off/on sequence fails when executing mmc_power_cycle().
Do you have any idea for this error case?

> >
> >>
> >> > >
> >> > >> >
> >> > >> >
> >> > >> >>> >> +static int dw_mci_switch_voltage(struct mmc_host *mmc, struct mmc_ios *ios)
> >> > >> >>> >> +{
> >> > >> >>> >> +     struct dw_mci_slot *slot = mmc_priv(mmc);
> >> > >> >>> >> +     struct dw_mci *host = slot->host;
> >> > >> >>> >> +     u32 uhs;
> >> > >> >>> >> +     u32 v18 = SDMMC_UHS_18V << slot->id;
> >> > >> >>> >> +     int min_uv, max_uv;
> >> > >> >>> >> +     int ret;
> >> > >> >>> >> +
> >> > >> >>> >> +     /*
> >> > >> >>> >> +      * Program the voltage.  Note that some instances of dw_mmc may use
> >> > >> >>> >> +      * the UHS_REG for this.  For other instances (like exynos) the UHS_REG
> >> > >> >>> >> +      * does no harm but you need to set the regulator directly.  Try both.
> >> > >> >>> >> +      */
> >> > >> >>> >> +     uhs = mci_readl(host, UHS_REG);
> >> > >> >>> >> +     if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_330) {
> >> > >> >>> >> +             min_uv = 2700000;
> >> > >> >>> >> +             max_uv = 3600000;
> >> > >> >>> >> +             uhs &= ~v18;
> >> > >> >>> >> +     } else {
> >> > >> >>> >> +             min_uv = 1700000;
> >> > >> >>> >> +             max_uv = 1950000;
> >> > >> >>> >> +             uhs |= v18;
> >> > >> >>> >> +     }
> >> > >> >>> >> +     if (!IS_ERR(mmc->supply.vqmmc)) {
> >> > >> >>> >> +             ret = regulator_set_voltage(mmc->supply.vqmmc, min_uv, max_uv);
> >> > >> >>> >> +
> >> > >> >>> >> +             /*
> >> > >> >>> >> +              * Only complain if regulator claims that it's not in the 1.8V
> >> > >> >>> >> +              * range.  This avoids a bunch of errors in the case that
> >> > >> >>> >> +              * we've got a fixed 1.8V regulator but the core SD code still
> >> > >> >>> >> +              * thinks it ought to try to switch to 3.3 and then back to 1.8
> >> > >> >>> >> +              */
> >> > >> >>> >> +             if (ret) {
> >> > >> >>> > I think if ret is error, printing message and returning error is good.
> >> > >> >>> > Currently, just returning '0' though it fails.
> >> > >> >> Any feedback?
> >> > >> >
> >> > >> > Whoops, right.  I think you're right that in the case it warns it
> >> > >> > should also return the error code.  In the case it doesn't warn it
> >> > >> > shouldn't.  Also: possibly we should use a trick like the mmc core
> >> > >> > does and use "regulator_count_voltages" to figure out if we're going
> >> > >> > to be able to switch voltages...
> >> > >> >
> >> > >> >>> > Artificially adding SDMMC_INT_CMD_DONE to pending is needed to complete cmd handling?
> >> > >> >>> > Is there any reason?
> >> > >> >>>
> >> > >> >>> I don't remember this for sure since I wrote this a long time ago.
> >> > >> >>> Maybe it's not needed?  I may have just been modeling on other
> >> > >> >>> interrupts.
> >> > >> >> If there is no specific reason, please remove it.
> >> > >> >
> >> > >> > OK, we'll see how Yuvaraj's testing goes without it.  My incredibly
> >> > >> > brief testing in our local Chrome OS 3.8 tree shows that the WiFi is
> >> > >> > not detected properly if I comment out the line:
> >> > >> >   dw_mci_cmd_interrupt(host,
> >> > >> >     pending | SDMMC_INT_CMD_DONE);
> >> > >> >
> >> > >> > It may be sufficient to simply schedule the tasklet or to do some
> >> > >> > other subset of dw_mci_cmd_interrupt().  Yuvaraj can confirm on the
> >> > >> > latest kernel and also investigate further.
> >> > > How about completing CMD without SDMMC_INT_CMD_DONE?
> >> > Without this tuning fails.
> >> > [    2.525284] mmc_host mmc0: Bus speed (slot 0) = 200000000Hz (slot
> >> > req 200000000Hz, actual 200000000HZ div = 0)
> >> > [  198.556573] random: nonblocking pool is initialized
> >> > [  240.226044] INFO: task kworker/u8:0:6 blocked for more than 120 seconds.
> >> > [  240.231276]       Not tainted 3.16.0-rc1-00010-g2f7a756-dirty #55
> >> > [  240.237359] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> >> > disables this message.
> >> > [  240.245150] kworker/u8:0    D c03a58a0     0     6      2 0x00000000
> >> > [  240.251487] Workqueue: kmmcd mmc_rescan
> >> > [  240.255297] [<c03a58a0>] (__schedule) from [<c03a5330>]
> >> > (schedule_timeout+0x130/0x170)
> >> > [  240.263201] [<c03a5330>] (schedule_timeout) from [<c03a6540>]
> >> > (wait_for_common+0xbc/0x14c)
> >> > [  240.271441] [<c03a6540>] (wait_for_common) from [<c02ca6e4>]
> >> > (mmc_wait_for_req_done+0x6c/0xf0)
> >> > [  240.280031] [<c02ca6e4>] (mmc_wait_for_req_done) from [<c02e3f10>]
> >> > (dw_mci_exynos_execute_tuning+0x1d4/0x2c4)
> >> > [  240.289919] [<c02e3f10>] (dw_mci_exynos_execute_tuning) from
> >> > [<c02e0198>] (dw_mci_execute_tuning+0x54/0xb4)
> >> > [  240.299635] [<c02e0198>] (dw_mci_execute_tuning) from [<c02cf47c>]
> >> > (mmc_init_card+0xeec/0x14ac)
> >> > [  240.308309] [<c02cf47c>] (mmc_init_card) from [<c02cfc34>]
> >> > (mmc_attach_mmc+0x8c/0x160)
> >> > [  240.316202] [<c02cfc34>] (mmc_attach_mmc) from [<c02cca0c>]
> >> > (mmc_rescan+0x2b0/0x308)
> >> > [  240.323924] [<c02cca0c>] (mmc_rescan) from [<c0032f60>]
> >> > (process_one_work+0xf8/0x364)
> >> > [  240.331732] [<c0032f60>] (process_one_work) from [<c0033800>]
> >> > (worker_thread+0x50/0x5a0)
> >> > [  240.339799] [<c0033800>] (worker_thread) from [<c0038e7c>]
> >> > (kthread+0xd8/0xf0)
> >> > [  240.346999] [<c0038e7c>] (kthread) from [<c000e438>]
> >> > (ret_from_fork+0x14/0x3c)
> >>
> >> Thank you for test.
> >> I want to clear it why CMD_DONE is related to tuning.
> > In my case, SDMMC_INT_CMD_DONE doesn't affect.
> I rechecked this.SDMMC_INT_CMD_DONE flag doesn't affect.Simply
> sheduling the tasklet is enough.Sorry,I misunderstood your comments
> earlier.
> > And do you check VOLT_SWITCH interrupt occurs twice during voltage-switching.
> No.Only once.

VOLT_SWITCH interrupt occurs totally twice. First is under CMD11. And second is after 1.8V voltage completed.
I actually found twice. Please check Voltage Switch Normal Scenario in the manual.

Thanks,
Seungwon Jeon

> > For last one, if-statement in dw_mci_interrupt() disturbs clearing interrupt.
> > if ((host->state == STATE_SENDING_CMD11) &&
> >
> > In addition, I suggest adding another flag instead of using host's state.
> > Can you consider it?
> Sure.I will check this.
> >
> > Thanks,
> > Seungwon Jeon
> >
> --
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