Re: [PATCH RFC 1/2] mmc: sdhci: Allow platform controlled voltage switching

From: Vijay Viswanath
Date: Tue Jul 17 2018 - 04:40:35 EST



On 7/17/2018 1:00 PM, Adrian Hunter wrote:
On 17/07/18 08:14, Vijay Viswanath wrote:


On 7/10/2018 4:37 PM, Adrian Hunter wrote:
On 21/06/18 15:23, Vijay Viswanath wrote:
Some controllers can have internal mechanism to inform the SW that it
is ready for voltage switching. For such controllers, changing voltage
before the HW is ready can result in various issues.

Add a quirk, which can be used by drivers of such controllers.

Signed-off-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
---
 drivers/mmc/host/sdhci.c | 20 +++++++++++++++-----
 drivers/mmc/host/sdhci.h | 2 ++
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 1c828e0..f0346d4 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1615,7 +1615,8 @@ void sdhci_set_power_noreg(struct sdhci_host *host,
unsigned char mode,
 void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ unsigned short vdd)
 {
-ÂÂÂ if (IS_ERR(host->mmc->supply.vmmc))
+ÂÂÂ if (IS_ERR(host->mmc->supply.vmmc) ||
+ÂÂÂÂÂÂÂÂÂÂÂ (host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))

I think you should provide your own ->set_power() instead of this


will do

ÂÂÂÂÂÂÂÂÂ sdhci_set_power_noreg(host, mode, vdd);
ÂÂÂÂÂ else
ÂÂÂÂÂÂÂÂÂ sdhci_set_power_reg(host, mode, vdd);
@@ -2009,7 +2010,9 @@ int sdhci_start_signal_voltage_switch(struct
mmc_host *mmc,
ÂÂÂÂÂÂÂÂÂ ctrl &= ~SDHCI_CTRL_VDD_180;
ÂÂÂÂÂÂÂÂÂ sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
 - if (!IS_ERR(mmc->supply.vqmmc)) {
+ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc) &&
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ !(host->quirks2 &
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {

And your own ->start_signal_voltage_switch()


sdhci_msm_start_signal_voltage_switch() would be an exact copy of
sdhci_start_signal_voltage_switch()..... will incorporate this if not using
quirk.

ÂÂÂÂÂÂÂÂÂÂÂÂÂ ret = mmc_regulator_set_vqmmc(mmc, ios);
ÂÂÂÂÂÂÂÂÂÂÂÂÂ if (ret) {
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_warn("%s: Switching to 3.3V signalling voltage
failed\n",
@@ -2032,7 +2035,8 @@ int sdhci_start_signal_voltage_switch(struct
mmc_host *mmc,
ÂÂÂÂÂ case MMC_SIGNAL_VOLTAGE_180:
ÂÂÂÂÂÂÂÂÂ if (!(host->flags & SDHCI_SIGNALING_180))
ÂÂÂÂÂÂÂÂÂÂÂÂÂ return -EINVAL;
-ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc)) {
+ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc) &&
+ÂÂÂÂÂÂÂÂÂÂÂ !(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {
ÂÂÂÂÂÂÂÂÂÂÂÂÂ ret = mmc_regulator_set_vqmmc(mmc, ios);
ÂÂÂÂÂÂÂÂÂÂÂÂÂ if (ret) {
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_warn("%s: Switching to 1.8V signalling voltage
failed\n",
@@ -3485,7 +3489,10 @@ int sdhci_setup_host(struct sdhci_host *host)
ÂÂÂÂÂÂ * the host can take the appropriate action if regulators are not
ÂÂÂÂÂÂ * available.
ÂÂÂÂÂÂ */
-ÂÂÂ ret = mmc_regulator_get_supply(mmc);
+ÂÂÂ if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))

Since we expect mmc_regulator_get_supply() to have been called, this could
be:

ÂÂÂÂif (!mmc->supply.vmmc) {
ÂÂÂÂÂÂÂ ret = mmc_regulator_get_supply(mmc);
ÂÂÂÂÂÂÂ enable_vqmmc = true;
ÂÂÂÂ} else {
ÂÂÂÂÂÂÂ ret = 0;
ÂÂÂÂ}
+ÂÂÂÂÂÂÂ ret = mmc_regulator_get_supply(mmc);
+ÂÂÂ else
+ÂÂÂÂÂÂÂ ret = 0;
ÂÂÂÂÂ if (ret)
ÂÂÂÂÂÂÂÂÂ return ret;
 @@ -3736,7 +3743,10 @@ int sdhci_setup_host(struct sdhci_host *host)
 Â /* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
ÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc)) {
-ÂÂÂÂÂÂÂ ret = regulator_enable(mmc->supply.vqmmc);
+ÂÂÂÂÂÂÂ if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))

And this could be:

ÂÂÂÂÂÂÂ if (enable_vqmmc)
ÂÂÂÂÂÂÂÂÂÂÂ ret = regulator_enable(mmc->supply.vqmmc);
ÂÂÂÂÂÂÂ else
ÂÂÂÂÂÂÂÂÂÂÂ ret = 0;
Â> However, you still need to ensure regulator_disable(mmc->supply.vqmmc) is
only called if regulator_enable() was called.
I missed this. Will cover it.

Also I missed one more place where we are doing regulator_disable. During
sdhci-msm unbinding, we would end up doing an extra regulator disable
(thanks Evan for pointing it out) in sdhci_remove_host.

To avoid the quirk( or having any flag), it would require copying the code
of sdhci_start_signal_voltage_switch() and sdhci_remove_host() and creating

You do not need to duplicate sdhci_remove_host(), just change it so that it
only disables what was enabled i.e.

if (host->vqmmc_enabled)
regulator_disable(mmc->supply.vqmmc);


Ok, so we will be adding a new flag "vqmmc_enabled" in sdhci_host, ryt ?
Just wanted to clarify

2 new functions in sdhci_msm layer which would do the exact same as above,
with just the regulator parts removed.

This looks messy (considering any future changes to the 2 sdhci API will
need to be copied to their duplicate sdhci_msm API) and a bit overkill to
avoid quirk. At the same time, I don't know how useful such a quirk would be
to other platform drivers.

Please let me know your view/suggestions.

Let's try without the quirk.


+ÂÂÂÂÂÂÂÂÂÂÂ ret = regulator_enable(mmc->supply.vqmmc);
+ÂÂÂÂÂÂÂ else
+ÂÂÂÂÂÂÂÂÂÂÂ ret = 0;
ÂÂÂÂÂÂÂÂÂ if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 1950000))
ÂÂÂÂÂÂÂÂÂÂÂÂÂ host->caps1 &= ~(SDHCI_SUPPORT_SDR104 |
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 23966f8..3b0c97a 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -450,6 +450,8 @@ struct sdhci_host {
ÂÂ * obtainable timeout.
ÂÂ */
 #define SDHCI_QUIRK2_DISABLE_HW_TIMEOUT (1<<17)
+/* Regulator voltage changes are being done from platform layer */
+#define SDHCI_QUIRK2_INTERNAL_PWR_CTLÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ (1<<18)

So maybe the quirk is not needed.

 Â int irq; /* Device IRQ */
ÂÂÂÂÂ void __iomem *ioaddr;ÂÂÂ /* Mapped address */



Thanks for the review & suggestions!
Vijay