[PATCH 3/3] mmc: dw_mmc: Support voltage changes
Doug Anderson
dianders at chromium.org
Wed Jun 25 10:46:15 PDT 2014
Seungwon,
On Wed, Jun 25, 2014 at 6:08 AM, Seungwon Jeon <tgih.jun at samsung.com> wrote:
> On Mon, June 23, 2014, Yuvaraj Kumar C D wrote:
>> Subject: [PATCH 3/3] mmc: dw_mmc: Support voltage changes
>>
>> From: Doug Anderson <dianders at chromium.org>
>>
>> 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.
>> Signed-off-by: Doug Anderson <dianders at chromium.org>
>> Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd at samsung.com>
>>
>> ---
>> 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:
* 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?
>
>> + }
>> +
>> 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.
>> if (!clock) {
>> mci_writel(host, CLKENA, 0);
>> - mci_send_cmd(slot,
>> - SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> + mci_send_cmd(slot, sdmmc_cmd_bits, 0);
>> } else if (clock != host->current_speed || force_clkinit) {
>> div = host->bus_hz / clock;
>> if (host->bus_hz % clock && host->bus_hz > clock)
>> @@ -804,15 +838,13 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>> mci_writel(host, CLKSRC, 0);
>>
>> /* inform CIU */
>> - mci_send_cmd(slot,
>> - SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> + mci_send_cmd(slot, sdmmc_cmd_bits, 0);
>>
>> /* set clock to desired speed */
>> mci_writel(host, CLKDIV, div);
>>
>> /* inform CIU */
>> - mci_send_cmd(slot,
>> - SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> + mci_send_cmd(slot, sdmmc_cmd_bits, 0);
>>
>> /* enable clock; only low power if no SDIO */
>> clk_en_a = SDMMC_CLKEN_ENABLE << slot->id;
>> @@ -821,8 +853,7 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>> mci_writel(host, CLKENA, clk_en_a);
>>
>> /* inform CIU */
>> - mci_send_cmd(slot,
>> - SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
>> + mci_send_cmd(slot, sdmmc_cmd_bits, 0);
>>
>> /* keep the clock with reflecting clock dividor */
>> slot->__clk_old = clock << div;
>> @@ -898,6 +929,17 @@ static void dw_mci_queue_request(struct dw_mci *host, struct dw_mci_slot *slot,
>>
>> slot->mrq = mrq;
>>
>> + if (host->state == STATE_WAITING_CMD11_DONE) {
>> + dev_warn(&slot->mmc->class_dev,
>> + "Voltage change didn't complete\n");
>> + /*
>> + * this case isn't expected to happen, so we can
>> + * either crash here or just try to continue on
>> + * in the closest possible state
>> + */
>> + host->state = STATE_IDLE;
>> + }
>> +
>> if (host->state == STATE_IDLE) {
>> host->state = STATE_SENDING_CMD;
>> dw_mci_start_request(host, slot);
>> @@ -993,6 +1035,9 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>> /* Slot specific timing and width adjustment */
>> dw_mci_setup_bus(slot, false);
>>
>> + if (slot->host->state == STATE_WAITING_CMD11_DONE && ios->clock != 0)
>> + slot->host->state = STATE_IDLE;
>> +
>> switch (ios->power_mode) {
>> case MMC_POWER_UP:
>> if ((!IS_ERR(mmc->supply.vmmc)) &&
>> @@ -1039,6 +1084,68 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>> }
>> }
>>
>> +static int dw_mci_card_busy(struct mmc_host *mmc)
>> +{
>> + struct dw_mci_slot *slot = mmc_priv(mmc);
>> + u32 status;
>> +
>> + /*
>> + * Check the busy bit which is low when DAT[3:0]
>> + * (the data lines) are 0000
>> + */
>> + status = mci_readl(slot->host, STATUS);
>> +
>> + return !!(status & SDMMC_STATUS_BUSY);
>> +}
>> +
>> +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.
>
>> + int cur_voltage = 0;
>> +
>> + cur_voltage = regulator_get_voltage(mmc->supply.vqmmc);
>> + if (cur_voltage < 1700000 || cur_voltage > 1950000)
>> + dev_warn(&mmc->class_dev,
>> + "Regulator set error %d: %d - %d\n",
>> + ret, min_uv, max_uv);
>> + }
>> + }
>> + mci_writel(host, UHS_REG, uhs);
>> +
>> + return 0;
>> +}
>> +
>> static int dw_mci_get_ro(struct mmc_host *mmc)
>> {
>> int read_only;
>> @@ -1180,6 +1287,9 @@ static const struct mmc_host_ops dw_mci_ops = {
>> .get_cd = dw_mci_get_cd,
>> .enable_sdio_irq = dw_mci_enable_sdio_irq,
>> .execute_tuning = dw_mci_execute_tuning,
>> + .card_busy = dw_mci_card_busy,
>> + .start_signal_voltage_switch = dw_mci_switch_voltage,
>> +
>> };
>>
>> static void dw_mci_request_end(struct dw_mci *host, struct mmc_request *mrq)
>> @@ -1203,7 +1313,11 @@ static void dw_mci_request_end(struct dw_mci *host, struct mmc_request *mrq)
>> dw_mci_start_request(host, slot);
>> } else {
>> dev_vdbg(host->dev, "list empty\n");
>> - host->state = STATE_IDLE;
>> +
>> + if (host->state == STATE_SENDING_CMD11)
>> + host->state = STATE_WAITING_CMD11_DONE;
>> + else
>> + host->state = STATE_IDLE;
>> }
>>
>> spin_unlock(&host->lock);
>> @@ -1314,8 +1428,10 @@ static void dw_mci_tasklet_func(unsigned long priv)
>>
>> switch (state) {
>> case STATE_IDLE:
>> + case STATE_WAITING_CMD11_DONE:
>> break;
>>
>> + case STATE_SENDING_CMD11:
>> case STATE_SENDING_CMD:
>> if (!test_and_clear_bit(EVENT_CMD_COMPLETE,
>> &host->pending_events))
>> @@ -1870,6 +1986,15 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
>> }
>>
>> if (pending) {
>> + /* Check volt switch first, since it can look like an error */
>> + if ((host->state == STATE_SENDING_CMD11) &&
>> + (pending & SDMMC_INT_VOLT_SWITCH)) {
>> + mci_writel(host, RINTSTS, SDMMC_INT_VOLT_SWITCH);
>> + pending &= ~SDMMC_INT_VOLT_SWITCH;
>> + dw_mci_cmd_interrupt(host,
>> + pending | SDMMC_INT_CMD_DONE);
> 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.
-Doug
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