Message-ID: <DM6PR11MB2876F5F9A801E449B266011CB8030@DM6PR11MB2876.namprd11.prod.outlook.com>
Date:   Fri, 16 Oct 2020 07:23:17 +0000
From:   "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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

Hi Ulf,

>-----Original Message-----
>From: Ulf Hansson <ulf.hansson@...aro.org>
>Sent: Tuesday, October 13, 2020 4:42 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 Fri, 9 Oct 2020 at 19:50, Zulkifli, Muhammad Husaini
><muhammad.husaini.zulkifli@...el.com> wrote:
>>
>> Hi,
>>
>> >-----Original Message-----
>> >From: Ulf Hansson <ulf.hansson@...aro.org>
>> >Sent: Friday, October 9, 2020 2:56 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 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.
>> >
>> >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.
>> As I mentioned The SDcard does not have its own voltage regulator.
>> It only uses the voltage rails on the mux input.
>>
>> There are 2 things need to be configured before getting the output voltage:
>>
>> 1) V_VDDIO_B :
>> Supplied voltage applied to I/O Rail which is controlled from the Always on
>domain using specific bits in AON_CFG1 register.
>> This is where we set for V_VDDIO_B using the
>keembay_sd_voltage_selection() to set either 1.8v or 3.3v depending on the bit
>value.
>> IMHO, we do not pinctrl to do this.
>>
>> 2) V_VDDIO_B_MAIN:
>> The output V_VDDIO_B_MAIN (OUT1) will be either V_3P3_MAIN (IN1) or
>> V_1P8_MAIN (IN2), depending on the state of GPIO expander Pin value. There
>is a POWER MUX involving here.
>> IMHO, we do not need any gpio regulator/regulator api hook up for this.
>> Most important thing, there is no regulator ic at all.
>> We still need to manually control and toggle the pin value.
>>
>> The final IO voltage is set by V_VDDIO_B (= V_VDDIO_B_MAIN after passing
>through voltage sense resistor).
>>
>> Hope this will clarify.
>
>I think I get it, thanks.
>
>Again, I haven't seen any reasons for why this can't be modelled as a pinctrl and
>a gpio-regulator. So, please convert it to that.
For gpio-regulator, I believe I could not use the current gpio-regulator.c framework as there is no consumer API for me to change the state of gpio pin during voltage switching.
Do I need to create a specific gpio-regulator driver under drivers/regulator for keem bay?
>
>Kind regards
>Uffe

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