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Subject: Re: [PATCH V2 02/12] pinctrl: tegra: add suspend and resume support
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com, tglx@linutronix.de,
        jason@lakedaemon.net, marc.zyngier@arm.com,
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Cc:     pdeschrijver@nvidia.com, pgaikwad@nvidia.com, sboyd@kernel.org,
        linux-clk@vger.kernel.org, linux-gpio@vger.kernel.org,
        jckuo@nvidia.com, josephl@nvidia.com, talho@nvidia.com,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        mperttunen@nvidia.com, spatra@nvidia.com, robh+dt@kernel.org,
        devicetree@vger.kernel.org
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 <c4e9fc53-f457-3e1d-8c73-8b98c30d9c69@nvidia.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <33707409-3a5c-c49b-20fb-130e3fa9f3b6@gmail.com>
Date:   Thu, 30 May 2019 00:33:08 +0300
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30.05.2019 0:27, Sowjanya Komatineni пишет:
> 
> On 5/29/19 2:25 PM, Dmitry Osipenko wrote:
>> 29.05.2019 23:56, Sowjanya Komatineni пишет:
>>> On 5/29/19 1:47 PM, Dmitry Osipenko wrote:
>>>> 29.05.2019 23:11, Sowjanya Komatineni пишет:
>>>>> On 5/29/19 12:32 PM, Dmitry Osipenko wrote:
>>>>>> 29.05.2019 21:14, Sowjanya Komatineni пишет:
>>>>>>> On 5/29/19 8:29 AM, Dmitry Osipenko wrote:
>>>>>>>> 29.05.2019 2:08, Sowjanya Komatineni пишет:
>>>>>>>>> This patch adds suspend and resume support for Tegra pinctrl
>>>>>>>>> driver
>>>>>>>>> and registers them to syscore so the pinmux settings are restored
>>>>>>>>> before the devices resume.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>>>>>>>>> ---
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra.c    | 68
>>>>>>>>> +++++++++++++++++++++++++++++++-
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra.h    |  3 ++
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra114.c |  1 +
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra124.c |  1 +
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra20.c  |  1 +
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra210.c |  1 +
>>>>>>>>>      drivers/pinctrl/tegra/pinctrl-tegra30.c  |  1 +
>>>>>>>>>      7 files changed, 75 insertions(+), 1 deletion(-)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/pinctrl/tegra/pinctrl-tegra.c
>>>>>>>>> b/drivers/pinctrl/tegra/pinctrl-tegra.c
>>>>>>>>> index a5008c066bac..bdc47e62c457 100644
>>>>>>>>> --- a/drivers/pinctrl/tegra/pinctrl-tegra.c
>>>>>>>>> +++ b/drivers/pinctrl/tegra/pinctrl-tegra.c
>>>>>>>>> @@ -28,11 +28,18 @@
>>>>>>>>>      #include <linux/pinctrl/pinmux.h>
>>>>>>>>>      #include <linux/pinctrl/pinconf.h>
>>>>>>>>>      #include <linux/slab.h>
>>>>>>>>> +#include <linux/syscore_ops.h>
>>>>>>>>>        #include "../core.h"
>>>>>>>>>      #include "../pinctrl-utils.h"
>>>>>>>>>      #include "pinctrl-tegra.h"
>>>>>>>>>      +#define EMMC2_PAD_CFGPADCTRL_0            0x1c8
>>>>>>>>> +#define EMMC4_PAD_CFGPADCTRL_0            0x1e0
>>>>>>>>> +#define EMMC_DPD_PARKING            (0x1fff << 14)
>>>>>>>>> +
>>>>>>>>> +static struct tegra_pmx *pmx;
>>>>>>>>> +
>>>>>>>>>      static inline u32 pmx_readl(struct tegra_pmx *pmx, u32
>>>>>>>>> bank, u32
>>>>>>>>> reg)
>>>>>>>>>      {
>>>>>>>>>          return readl(pmx->regs[bank] + reg);
>>>>>>>>> @@ -629,6 +636,50 @@ static void
>>>>>>>>> tegra_pinctrl_clear_parked_bits(struct tegra_pmx *pmx)
>>>>>>>>>          }
>>>>>>>>>      }
>>>>>>>>>      +static int __maybe_unused tegra_pinctrl_suspend(void)
>>>>>>>>> +{
>>>>>>>>> +    u32 *backup_regs = pmx->backup_regs;
>>>>>>>>> +    u32 *regs;
>>>>>>>>> +    int i, j;
>>>>>>>>> +
>>>>>>>>> +    for (i = 0; i < pmx->nbanks; i++) {
>>>>>>>>> +        regs = pmx->regs[i];
>>>>>>>>> +        for (j = 0; j < pmx->reg_bank_size[i] / 4; j++)
>>>>>>>>> +            *backup_regs++ = readl(regs++);
>>>>>>>>> +    }
>>>>>>>>> +
>>>>>>>>> +    return pinctrl_force_sleep(pmx->pctl);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void __maybe_unused tegra_pinctrl_resume(void)
>>>>>>>>> +{
>>>>>>>>> +    u32 *backup_regs = pmx->backup_regs;
>>>>>>>>> +    u32 *regs;
>>>>>>>>> +    u32 val;
>>>>>>>>> +    int i, j;
>>>>>>>>> +
>>>>>>>>> +    for (i = 0; i < pmx->nbanks; i++) {
>>>>>>>>> +        regs = pmx->regs[i];
>>>>>>>>> +        for (j = 0; j < pmx->reg_bank_size[i] / 4; j++)
>>>>>>>>> +            writel(*backup_regs++, regs++);
>>>>>>>>> +    }
>>>>>>>>> +
>>>>>>>>> +    if (pmx->soc->has_park_padcfg) {
>>>>>>>>> +        val = pmx_readl(pmx, 0, EMMC2_PAD_CFGPADCTRL_0);
>>>>>>>>> +        val &= ~EMMC_DPD_PARKING;
>>>>>>>>> +        pmx_writel(pmx, val, 0, EMMC2_PAD_CFGPADCTRL_0);
>>>>>>>>> +
>>>>>>>>> +        val = pmx_readl(pmx, 0, EMMC4_PAD_CFGPADCTRL_0);
>>>>>>>>> +        val &= ~EMMC_DPD_PARKING;
>>>>>>>>> +        pmx_writel(pmx, val, 0, EMMC4_PAD_CFGPADCTRL_0);
>>>>>>>>> +    }
>>>>>>>>> +}
>>>>>>>>>
>>>>>>>> But the CFGPADCTRL registers are already programmed by restoring
>>>>>>>> the
>>>>>>>> backup_regs and hence the relevant EMMC's are already unparked.
>>>>>>>> Hence
>>>>>>>> why do you need to force-unpark both of the EMMC's? What if EMMC is
>>>>>>>> unpopulated on a board, why do you need to unpark it then?
>>>>>>> PARK bit for EMMC2/EMMC4 (EMMC2_PAD_CFGPADCTRL and
>>>>>>> EMMC4_PAD_CFGPADCTRL)
>>>>>>> are not part of pinmux.
>>>>>>>
>>>>>>> They are part of CFGPADCTRL register so pinctrl driver pingroup
>>>>>>> doesn't
>>>>>>> include these registers.
>>>>>> I'm looking at the tegra210_groups and it clearly has these both
>>>>>> registers as a part of pinctrl setup because the rest of the bits
>>>>>> configure drive of the pads.
>>>>>>
>>>>>>    From pinctrl-tegra210.c:
>>>>>>
>>>>>> #define DRV_PINGROUP_REG_A        0x8d4    /* bank 0 */
>>>>>>
>>>>>> DRV_PINGROUP(sdmmc2, 0xa9c, 2,  6,  8,  6,  28, 2,  30, 2),
>>>>>> DRV_PINGROUP(sdmmc4, 0xab4, 2,  6,  8,  6,  28, 2,  30, 2),
>>>>>>
>>>>>> ...
>>>>>>
>>>>>> 0xa9c - 0x8d4 = 0x1c8
>>>>>> 0xab4 - 0x8d4 = 0x1e0
>>>>>>
>>>>>> Hence the PARK bits are already getting unset by restoring the
>>>>>> backup_regs because the CFGPADCTRL registers are a part of the
>>>>>> "bank 0"
>>>>>> registers.
>>>>>>
>>>>>> Am I still missing something?
>>>>> DRV_PINGROUP parked_bit is -1 and will not be programmed so store and
>>>>> restore will not take care of it.
>>>>>
>>>>> Also EMMC PADCFG is the only padcfg register which has parked bit and
>>>>> for other IO pads its part of pinmux
>>>> You're storing raw values of all of the PINCTRL registers and then
>>>> restoring the raw values (if I'm not misreading that part on the
>>>> patch),
>>>> it's absolutely meaningless that DRV_PINGROUP doesn't define the PARK
>>>> bits.
>>>>
>>>> In a result, the backup_regs array contains raw CFGPADCTRL value with
>>>> the PARK bits being unset on store, that value is written out on the
>>>> restore as-is and hence the PARK bits are getting unset as well.
>>>>
>>>> And why DRV_PINGROUP misses PARK bits for the EMMC's? Looks like a
>>>> driver's drawback that need to be addressed.
>>> Parked bits from padcfg are available only for couple of EMMC registers.
>>>
>>> default PARK bits are set so stored value contains park bit set. on
>>> resume, after restoring park bit is cleared.
>> TRM says that the PARK bits are set on HW reset (and on DPD IIUC) and
>> then SW should unset the bits. I assume that the PARK bits of the EMMC
>> pads are unset by bootloader and that's why it doesn't cause problems
>> for kernel, in oppose to PARK bits of the rest of pinmux that are unset
>> by the driver in tegra_pinctrl_clear_parked_bits() on driver's probe.
>>
>>> on subsequence DPD entry, stored value contains park bit 0 and HW clamps
>>> park bit to logic 1 during DPD entry and cleared again on resume.
>> I assume that EMMC won't work properly if pads are "parked" and the PARK
>> bits should be in unset state on kernel boot-up as I wrote above, hence
>> stored value should always contain 0 for the EMMC PARK bits. No?
> 
> On bootup, pads still works. PARK bit is to keep pads in DPD once they
> enter into DPD (LP0) and on resume they need to be cleared to be out of DPD
> 
> 

Ah okay, thank you for the clarification.

Indeed, it will be better to unset the PARK bits in
pinctrl_clear_parked_bits, as you suggested in the other email. Seems it
should be simple to turn parked_bit into parked_bitmask.