linux-kernel - Re: [PATCH v4 4/4] mmc: sdhci-of-arasan: Enable UHS-1 support for Keem Bay SOC

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Date:   Fri, 9 Oct 2020 09:25:11 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
Cc:     "Hunter, Adrian" <adrian.hunter@...el.com>,
        Michal Simek <michal.simek@...inx.com>,
        "Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Raja Subramanian, Lakshmi Bai" 
        <lakshmi.bai.raja.subramanian@...el.com>,
        "Wan Mohamad, Wan Ahmad Zainie" 
        <wan.ahmad.zainie.wan.mohamad@...el.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v4 4/4] mmc: sdhci-of-arasan: Enable UHS-1 support for
 Keem Bay SOC



On 09. 10. 20 8:56, Ulf Hansson wrote:
> On Thu, 8 Oct 2020 at 19:21, Zulkifli, Muhammad Husaini
> <muhammad.husaini.zulkifli@...el.com> wrote:
>>
>> Hi,
>>
>>> -----Original Message-----
>>> From: Ulf Hansson <ulf.hansson@...aro.org>
>>> Sent: Thursday, October 8, 2020 11:19 PM
>>> To: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@...el.com>
>>> Cc: Hunter, Adrian <adrian.hunter@...el.com>; Michal Simek
>>> <michal.simek@...inx.com>; Shevchenko, Andriy
>>> <andriy.shevchenko@...el.com>; linux-mmc@...r.kernel.org; Linux ARM
>>> <linux-arm-kernel@...ts.infradead.org>; Linux Kernel Mailing List <linux-
>>> kernel@...r.kernel.org>; Raja Subramanian, Lakshmi Bai
>>> <lakshmi.bai.raja.subramanian@...el.com>; Wan Mohamad, Wan Ahmad
>>> Zainie <wan.ahmad.zainie.wan.mohamad@...el.com>; Arnd Bergmann
>>> <arnd@...db.de>
>>> Subject: Re: [PATCH v4 4/4] mmc: sdhci-of-arasan: Enable UHS-1 support for
>>> Keem Bay SOC
>>>
>>> On Thu, 8 Oct 2020 at 12:54, Zulkifli, Muhammad Husaini
>>> <muhammad.husaini.zulkifli@...el.com> wrote:
>>>>
>>>> Hi,
>>>>
>>>>> -----Original Message-----
>>>>> From: Ulf Hansson <ulf.hansson@...aro.org>
>>>>> Sent: Thursday, October 8, 2020 5:28 PM
>>>>> To: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@...el.com>
>>>>> Cc: Hunter, Adrian <adrian.hunter@...el.com>; Michal Simek
>>>>> <michal.simek@...inx.com>; Shevchenko, Andriy
>>>>> <andriy.shevchenko@...el.com>; linux-mmc@...r.kernel.org; Linux ARM
>>>>> <linux-arm-kernel@...ts.infradead.org>; Linux Kernel Mailing List
>>>>> <linux- kernel@...r.kernel.org>; Raja Subramanian, Lakshmi Bai
>>>>> <lakshmi.bai.raja.subramanian@...el.com>; Wan Mohamad, Wan Ahmad
>>>>> Zainie <wan.ahmad.zainie.wan.mohamad@...el.com>; Arnd Bergmann
>>>>> <arnd@...db.de>
>>>>> Subject: Re: [PATCH v4 4/4] mmc: sdhci-of-arasan: Enable UHS-1
>>>>> support for Keem Bay SOC
>>>>>
>>>>> On Thu, 8 Oct 2020 at 04:12, <muhammad.husaini.zulkifli@...el.com>
>>> wrote:
>>>>>>
>>>>>> From: Muhammad Husaini Zulkifli
>>>>>> <muhammad.husaini.zulkifli@...el.com>
>>>>>>
>>>>>> Voltage switching sequence is needed to support UHS-1 interface.
>>>>>> There are 2 places to control the voltage.
>>>>>> 1) By setting the AON register using firmware driver calling
>>>>>> system-level platform management layer (SMC) to set the register.
>>>>>> 2) By controlling the GPIO expander value to drive either 1.8V or
>>>>>> 3.3V for power mux input.
>>>>>>
>>>>>> Signed-off-by: Muhammad Husaini Zulkifli
>>>>>> <muhammad.husaini.zulkifli@...el.com>
>>>>>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>
>>>>>> Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>
>>>>>> ---
>>>>>>  drivers/mmc/host/sdhci-of-arasan.c | 126
>>>>>> +++++++++++++++++++++++++++++
>>>>>>  1 file changed, 126 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/mmc/host/sdhci-of-arasan.c
>>>>>> b/drivers/mmc/host/sdhci-of-arasan.c
>>>>>> index 46aea6516133..ea2467b0073d 100644
>>>>>> --- a/drivers/mmc/host/sdhci-of-arasan.c
>>>>>> +++ b/drivers/mmc/host/sdhci-of-arasan.c
>>>>>> @@ -16,6 +16,7 @@
>>>>>>   */
>>>>>>
>>>>>>  #include <linux/clk-provider.h>
>>>>>> +#include <linux/gpio/consumer.h>
>>>>>>  #include <linux/mfd/syscon.h>
>>>>>>  #include <linux/module.h>
>>>>>>  #include <linux/of_device.h>
>>>>>> @@ -23,6 +24,7 @@
>>>>>>  #include <linux/regmap.h>
>>>>>>  #include <linux/of.h>
>>>>>>  #include <linux/firmware/xlnx-zynqmp.h>
>>>>>> +#include <linux/firmware/intel/keembay_firmware.h>
>>>>>>
>>>>>>  #include "cqhci.h"
>>>>>>  #include "sdhci-pltfm.h"
>>>>>> @@ -136,6 +138,7 @@ struct sdhci_arasan_clk_data {
>>>>>>   * @soc_ctl_base:      Pointer to regmap for syscon for soc_ctl registers.
>>>>>>   * @soc_ctl_map:       Map to get offsets into soc_ctl registers.
>>>>>>   * @quirks:            Arasan deviations from spec.
>>>>>> + * @uhs_gpio:          Pointer to the uhs gpio.
>>>>>>   */
>>>>>>  struct sdhci_arasan_data {
>>>>>>         struct sdhci_host *host;
>>>>>> @@ -150,6 +153,7 @@ struct sdhci_arasan_data {
>>>>>>         struct regmap   *soc_ctl_base;
>>>>>>         const struct sdhci_arasan_soc_ctl_map *soc_ctl_map;
>>>>>>         unsigned int    quirks;
>>>>>> +       struct gpio_desc *uhs_gpio;
>>>>>>
>>>>>>  /* Controller does not have CD wired and will not function
>>>>>> normally without
>>>>> */
>>>>>>  #define SDHCI_ARASAN_QUIRK_FORCE_CDTEST        BIT(0)
>>>>>> @@ -361,6 +365,112 @@ static int sdhci_arasan_voltage_switch(struct
>>>>> mmc_host *mmc,
>>>>>>         return -EINVAL;
>>>>>>  }
>>>>>>
>>>>>> +static int sdhci_arasan_keembay_voltage_switch(struct mmc_host
>>> *mmc,
>>>>>> +                                      struct mmc_ios *ios) {
>>>>>> +       struct sdhci_host *host = mmc_priv(mmc);
>>>>>> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>>>>>> +       struct sdhci_arasan_data *sdhci_arasan =
>>> sdhci_pltfm_priv(pltfm_host);
>>>>>> +       u16 ctrl_2, clk;
>>>>>> +       int ret;
>>>>>> +
>>>>>> +       switch (ios->signal_voltage) {
>>>>>> +       case MMC_SIGNAL_VOLTAGE_180:
>>>>>> +               clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
>>>>>> +               clk &= ~SDHCI_CLOCK_CARD_EN;
>>>>>> +               sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
>>>>>> +
>>>>>> +               clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
>>>>>> +               if (clk & SDHCI_CLOCK_CARD_EN)
>>>>>> +                       return -EAGAIN;
>>>>>> +
>>>>>> +               sdhci_writeb(host, SDHCI_POWER_ON | SDHCI_POWER_180,
>>>>>> +                                  SDHCI_POWER_CONTROL);
>>>>>> +
>>>>>> +               /*
>>>>>> +                * Set VDDIO_B voltage to Low for 1.8V
>>>>>> +                * which is controlling by GPIO Expander.
>>>>>> +                */
>>>>>> +               gpiod_set_value_cansleep(sdhci_arasan->uhs_gpio,
>>>>>> + 0);
>>>>>> +
>>>>>> +               /*
>>>>>> +                * This is like a final gatekeeper. Need to ensure changed
>>> voltage
>>>>>> +                * is settled before and after turn on this bit.
>>>>>> +                */
>>>>>> +               usleep_range(1000, 1100);
>>>>>> +
>>>>>> +               ret =
>>> keembay_sd_voltage_selection(KEEMBAY_SET_1V8_VOLT);
>>>>>> +               if (ret)
>>>>>> +                       return ret;
>>>>>> +
>>>>>> +               usleep_range(1000, 1100);
>>>>>
>>>>> No, sorry, but I don't like this.
>>>>>
>>>>> This looks like a GPIO regulator with an extension of using the
>>>>> keembay_sd_voltage_selection() thingy. I think you can model these
>>>>> things behind a regulator and hook it up as a vqmmc supply in DT
>>>>> instead. BTW, this is the common way we deal with these things for mmc
>>> host drivers.
>>>>
>>>> The SDcard for Keem Bay SOC does not have its own voltage regulator.
>>>> There are 2 places to control the voltage.
>>>> 1) By setting the AON register calling system-level platform management
>>> layer (SMC)
>>>>    to set the I/O pads voltage for particular GPIOs line for clk,data and cmd.
>>>>    The reason why I use this keembay_sd_voltage_selection() via smccc
>>> interface it because during voltage switching
>>>>    I need to access to AON register. On a secure system, we could not
>>> directly access to AON register due to some security concern from driver side,
>>> thus
>>>>    cannot exposed any register or address.
>>>> 2) By controlling the GPIO expander value to drive either 1.8V or 3.3V for
>>> power mux input.
>>>
>>> I see, thanks for clarifying.
>>>
>>> To me, it sounds like the best fit is to implement a pinctrl (to manage the I/O
>>> pads) and a GPIO regulator.
>>>
>> Even with pinctrl, i still need to use the keembay_sd_voltage_selection() thingy for AON register.
> 
> Yes, I am fine by that.
> 
> Although, as it's really a pinctrl, it deserves to be modelled like
> that. Not as a soc specific hack in a mmc host driver.

:-)

> 
>> Plus, the GPIO pin that control the sd-voltage is in GPIO Expander not using Keembay SOC GPIO Pin.
>> The best option is using the gpio consumer function to toggle the pin.
> 
> As I said, please no.
> 
> The common way to model this is as a GPIO regulator. In this way, you
> can even rely on existing mmc DT bindings. All you have to do is to
> hook up a vqmmc supply to the mmc node.

regulators were mentioned here in v1
https://lore.kernel.org/linux-arm-kernel/21d34b75-5947-e115-7c9a-6d068375bbdd@xilinx.com/

> 
> To be clear, as long as there are no arguments for why a pinctrl and
> GPIO regulator can't be used - I am not going to pick up the patches.

I mentioned pinctrl here also in v1 thread.
http://lore.kernel.org/r/6b1c9c71-ca10-47b0-895c-adafc6881063@xilinx.com

Thanks,
Michal