Hi Jaehoon,
On 02/02/21 3:40 am, Jaehoon Chung wrote:
> Hi Aswath,
>
> On 1/29/21 11:47 PM, Aswath Govindraju wrote:
>> From: Faiz Abbas <faiz_abbas at ti.com>
>>
>> Add a set_voltage() function which handles the switch from 3.3V to 1.8V
>> for SD card UHS modes.
>>
>> Signed-off-by: Faiz Abbas <faiz_abbas at ti.com>
>> Signed-off-by: Aswath Govindraju <a-govindraju at ti.com>
>> ---
>> drivers/mmc/sdhci.c | 73 +++++++++++++++++++++++++++++++++++++++++++++
>> include/sdhci.h | 10 +++++++
>> 2 files changed, 83 insertions(+)
>>
>> diff --git a/drivers/mmc/sdhci.c b/drivers/mmc/sdhci.c
>> index 06289343124e..276b6a08e571 100644
>> --- a/drivers/mmc/sdhci.c
>> +++ b/drivers/mmc/sdhci.c
>> @@ -20,6 +20,7 @@
>> #include <linux/delay.h>
>> #include <linux/dma-mapping.h>
>> #include <phys2bus.h>
>> +#include <power/regulator.h>
>>
>> static void sdhci_reset(struct sdhci_host *host, u8 mask)
>> {
>> @@ -509,6 +510,78 @@ void sdhci_set_uhs_timing(struct sdhci_host *host)
>> sdhci_writew(host, reg, SDHCI_HOST_CONTROL2);
>> }
>>
>> +static void sdhci_set_voltage(struct sdhci_host *host)
>> +{
>> + if (IS_ENABLED(CONFIG_MMC_IO_VOLTAGE)) {
>> + struct mmc *mmc = (struct mmc *)host->mmc;
>> + u32 ctrl;
>> +
>> + ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>> +
>> + switch (mmc->signal_voltage) {
>> + case MMC_SIGNAL_VOLTAGE_330:
>> +#if CONFIG_IS_ENABLED(DM_REGULATOR)
>> + if (mmc->vqmmc_supply) {
>> + if (regulator_set_enable_if_allowed(mmc->vqmmc_supply, false)) {
>> + pr_err("failed to disable vqmmc-supply\n");
>> + return;
>> + }
>> +
>> + if (regulator_set_value(mmc->vqmmc_supply, 3300000)) {
>> + pr_err("failed to set vqmmc-voltage to 3.3V\n");
>> + return;
>> + }
>> +
>> + if (regulator_set_enable_if_allowed(mmc->vqmmc_supply, true)) {
>> + pr_err("failed to enable vqmmc-supply\n");
>> + return;
>> + }
>> + }
>> +#endif
>> + /* 3.3V regulator output should be stable within 5 ms */
>> + mdelay(5);
>> + if (IS_SD(mmc)) {
>> + ctrl &= ~SDHCI_CTRL_VDD_180;
>> + sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>> + }
>
> According to Specification, after Signal bit was changed to 0 from 1, it needs to wait for stable within 5ms.
> Isn't it right that mdelay(5) locates at here?
>
I searched the spec for this and found the following line in it,
```
If this status is not supported, Host Driver should take more than 5ms for
stable time of host voltage regulator from changing 1.8V Signaling
Enable. Specific Host Driver may use a specific time, which is provided by
Host System, instead of using 5ms.
```
This is from the row of "Host Regulator Voltage Stable" in table
describing "Present state register", "PartA2_SD
Host_Controller_Simplified_Specification_Ver4.20" document, page 66.
The status mentioned is about host regulator voltage stable. Yes I can
see that it has been mentioned that host driver has to wait for 5ms
after changing the 1.8V signal enable bit. In that case I suppose the
same has to be done at [1] as well right ?
>> + break;
>> + case MMC_SIGNAL_VOLTAGE_180:
>> +#if CONFIG_IS_ENABLED(DM_REGULATOR)
>> + if (mmc->vqmmc_supply) {
>> + if (regulator_set_enable_if_allowed(mmc->vqmmc_supply, false)) {
>> + pr_err("failed to disable vqmmc-supply\n");
>> + return;
>> + }
>> +
>> + if (regulator_set_value(mmc->vqmmc_supply, 1800000)) {
>> + pr_err("failed to set vqmmc-voltage to 1.8V\n");
>> + return;
>> + }
>> +
>> + if (regulator_set_enable_if_allowed(mmc->vqmmc_supply, true)) {
>> + pr_err("failed to enable vqmmc-supply\n");
>> + return;
>> + }
>> + }
>> +#endif
>> + if (IS_SD(mmc)) {
>> + ctrl |= SDHCI_CTRL_VDD_180;
>> + sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>> + }
[1]
For reference, I have also attached the page from where the above line
was taken.
Thank you for pointing it out. I will post a re-spin fixing it.
Thanks,
Aswath
>> + break;
>> + default:
>> + /* No signal voltage switch required */
>> + return;
>> + }
>> + }
>> +}
>> +
>> +void sdhci_set_control_reg(struct sdhci_host *host)
>> +{
>> + sdhci_set_voltage(host);
>> + sdhci_set_uhs_timing(host);
>> +}
>> +
>> #ifdef CONFIG_DM_MMC
>> static int sdhci_set_ios(struct udevice *dev)
>> {
>> diff --git a/include/sdhci.h b/include/sdhci.h
>> index 3e5a64981857..0ae9471ad749 100644
>> --- a/include/sdhci.h
>> +++ b/include/sdhci.h
>> @@ -491,6 +491,16 @@ void sdhci_set_uhs_timing(struct sdhci_host *host);
>> /* Export the operations to drivers */
>> int sdhci_probe(struct udevice *dev);
>> int sdhci_set_clock(struct mmc *mmc, unsigned int clock);
>> +
>> +/**
>> + * sdhci_set_control_reg - Set control registers
>> + *
>> + * This is used set up control registers for voltage level and UHS speed
>> + * mode.
>> + *
>> + * @host: SDHCI host structure
>> + */
>> +void sdhci_set_control_reg(struct sdhci_host *host);
>> extern const struct dm_mmc_ops sdhci_ops;
>> #else
>> #endif
>>
>
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