linux-kernel - Re: [PATCH 8/9] mmc: mmci: sdmmc: add voltage switch functions

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Date:   Mon, 27 Jan 2020 14:50:07 +0100
From:   Ludovic BARRE <ludovic.barre@...com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH 8/9] mmc: mmci: sdmmc: add voltage switch functions

hi Ulf

Le 1/24/20 à 2:16 PM, Ulf Hansson a écrit :
> On Fri, 10 Jan 2020 at 14:49, Ludovic Barre <ludovic.barre@...com> wrote:
>>
>> To prepare the voltage switch procedure, the VSWITCHEN bit must be
>> set before sending the cmd11.
>> To confirm completion of voltage switch, the VSWEND flag must be
>> checked.
>>
>> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
>> ---
>>   drivers/mmc/host/mmci.h             |  4 +++
>>   drivers/mmc/host/mmci_stm32_sdmmc.c | 40 ++++++++++++++++++++++++++++-
>>   2 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
>> index c04a144259a2..3634f98ad2d8 100644
>> --- a/drivers/mmc/host/mmci.h
>> +++ b/drivers/mmc/host/mmci.h
>> @@ -165,6 +165,7 @@
>>   /* Extended status bits for the STM32 variants */
>>   #define MCI_STM32_BUSYD0       BIT(20)
>>   #define MCI_STM32_BUSYD0END    BIT(21)
>> +#define MCI_STM32_VSWEND       BIT(25)
>>
>>   #define MMCICLEAR              0x038
>>   #define MCI_CMDCRCFAILCLR      (1 << 0)
>> @@ -182,6 +183,9 @@
>>   #define MCI_ST_SDIOITC         (1 << 22)
>>   #define MCI_ST_CEATAENDC       (1 << 23)
>>   #define MCI_ST_BUSYENDC                (1 << 24)
>> +/* Extended clear bits for the STM32 variants */
>> +#define MCI_STM32_VSWENDC      BIT(25)
>> +#define MCI_STM32_CKSTOPC      BIT(26)
>>
>>   #define MMCIMASK0              0x03c
>>   #define MCI_CMDCRCFAILMASK     (1 << 0)
>> diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
>> index 10059fa19f4a..9f43cf947c5f 100644
>> --- a/drivers/mmc/host/mmci_stm32_sdmmc.c
>> +++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
>> @@ -263,7 +263,9 @@ static void mmci_sdmmc_set_pwrreg(struct mmci_host *host, unsigned int pwr)
>>          struct mmc_ios ios = host->mmc->ios;
>>          struct sdmmc_dlyb *dlyb = host->variant_priv;
>>
>> -       pwr = host->pwr_reg_add;
>> +       /* adds OF options and preserves voltage switch bits */
>> +       pwr = host->pwr_reg_add |
>> +               (host->pwr_reg & (MCI_STM32_VSWITCHEN | MCI_STM32_VSWITCH));
>>
>>          sdmmc_dlyb_input_ck(dlyb);
>>
>> @@ -454,6 +456,40 @@ static int sdmmc_execute_tuning(struct mmc_host *mmc, u32 opcode)
>>          return sdmmc_dlyb_phase_tuning(host, opcode);
>>   }
>>
>> +static void sdmmc_prep_vswitch(struct mmci_host *host)
>> +{
>> +       /* clear the voltage switch completion flag */
>> +       writel_relaxed(MCI_STM32_VSWENDC, host->base + MMCICLEAR);
>> +       /* enable Voltage switch procedure */
>> +       mmci_write_pwrreg(host, host->pwr_reg | MCI_STM32_VSWITCHEN);
>> +}
>> +
>> +static int sdmmc_vswitch(struct mmci_host *host, struct mmc_ios *ios)
>> +{
>> +       unsigned long flags;
>> +       u32 status;
>> +       int ret = 0;
>> +
>> +       if (ios->signal_voltage == MMC_SIGNAL_VOLTAGE_180) {
>> +               spin_lock_irqsave(&host->lock, flags);
>> +               mmci_write_pwrreg(host, host->pwr_reg | MCI_STM32_VSWITCH);
>> +               spin_unlock_irqrestore(&host->lock, flags);
>> +
>> +               /* wait voltage switch completion while 10ms */
>> +               ret = readl_relaxed_poll_timeout(host->base + MMCISTATUS,
>> +                                                status,
>> +                                                (status & MCI_STM32_VSWEND),
>> +                                                10, 10000);
>> +
>> +               writel_relaxed(MCI_STM32_VSWENDC | MCI_STM32_CKSTOPC,
>> +                              host->base + MMCICLEAR);
>> +               mmci_write_pwrreg(host, host->pwr_reg &
>> +                                 ~(MCI_STM32_VSWITCHEN | MCI_STM32_VSWITCH));
>> +       }
> 
> Don't you need to manage things when resetting to
> MMC_SIGNAL_VOLTAGE_330, which for example happens during a card
> removal or at system suspend/resume?
> 

The VSWITCH sequence is used only for 3.3V to 1.8V.
If there are: card remove | suspend/resume.
The power cycle of sdmmc must be reinitialised
and the reset is mandatory.

>> +
>> +       return ret;
>> +}
>> +
>>   static struct mmci_host_ops sdmmc_variant_ops = {
>>          .validate_data = sdmmc_idma_validate_data,
>>          .prep_data = sdmmc_idma_prep_data,
>> @@ -465,6 +501,8 @@ static struct mmci_host_ops sdmmc_variant_ops = {
>>          .set_clkreg = mmci_sdmmc_set_clkreg,
>>          .set_pwrreg = mmci_sdmmc_set_pwrreg,
>>          .busy_complete = sdmmc_busy_complete,
>> +       .prep_volt_switch = sdmmc_prep_vswitch,
>> +       .volt_switch = sdmmc_vswitch,
>>   };
>>
>>   void sdmmc_variant_init(struct mmci_host *host)
>> --
>> 2.17.1
>>
> 
> Kind regards
> Uffe
>