Re: [PATCH v4 4/4] mmc: sdhci-of-arasan: Enable UHS-1 support for Keem Bay SOC
From: Michal Simek
Date: Fri Oct 09 2020 - 03:25:34 EST
On 09. 10. 20 8:56, Ulf Hansson wrote:
> On Thu, 8 Oct 2020 at 19:21, Zulkifli, Muhammad Husaini
> <muhammad.husaini.zulkifli@xxxxxxxxx> wrote:
>>
>> Hi,
>>
>>> -----Original Message-----
>>> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>>> Sent: Thursday, October 8, 2020 11:19 PM
>>> To: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@xxxxxxxxx>
>>> Cc: Hunter, Adrian <adrian.hunter@xxxxxxxxx>; Michal Simek
>>> <michal.simek@xxxxxxxxxx>; Shevchenko, Andriy
>>> <andriy.shevchenko@xxxxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx; Linux ARM
>>> <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux-
>>> kernel@xxxxxxxxxxxxxxx>; Raja Subramanian, Lakshmi Bai
>>> <lakshmi.bai.raja.subramanian@xxxxxxxxx>; Wan Mohamad, Wan Ahmad
>>> Zainie <wan.ahmad.zainie.wan.mohamad@xxxxxxxxx>; Arnd Bergmann
>>> <arnd@xxxxxxxx>
>>> 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@xxxxxxxxx> wrote:
>>>>
>>>> Hi,
>>>>
>>>>> -----Original Message-----
>>>>> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>>>>> Sent: Thursday, October 8, 2020 5:28 PM
>>>>> To: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@xxxxxxxxx>
>>>>> Cc: Hunter, Adrian <adrian.hunter@xxxxxxxxx>; Michal Simek
>>>>> <michal.simek@xxxxxxxxxx>; Shevchenko, Andriy
>>>>> <andriy.shevchenko@xxxxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx; Linux ARM
>>>>> <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Linux Kernel Mailing List
>>>>> <linux- kernel@xxxxxxxxxxxxxxx>; Raja Subramanian, Lakshmi Bai
>>>>> <lakshmi.bai.raja.subramanian@xxxxxxxxx>; Wan Mohamad, Wan Ahmad
>>>>> Zainie <wan.ahmad.zainie.wan.mohamad@xxxxxxxxx>; Arnd Bergmann
>>>>> <arnd@xxxxxxxx>
>>>>> 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@xxxxxxxxx>
>>> wrote:
>>>>>>
>>>>>> From: Muhammad Husaini Zulkifli
>>>>>> <muhammad.husaini.zulkifli@xxxxxxxxx>
>>>>>>
>>>>>> 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@xxxxxxxxx>
>>>>>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
>>>>>> Reviewed-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>>>>>> ---
>>>>>> 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@xxxxxxxxxx/
>
> 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@xxxxxxxxxx
Thanks,
Michal