linux-kernel - Re: [PATCH 1/2] ALSA: cs35l41: Add shared boost feature

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Date:   Tue, 7 Feb 2023 15:49:28 +0000
From:   Lucas Tanure <lucas.tanure@...labora.com>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     David Rhodes <david.rhodes@...rus.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, patches@...nsource.cirrus.com,
        linux-kernel@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH 1/2] ALSA: cs35l41: Add shared boost feature

On 07-02-2023 11:48, Charles Keepax wrote:
> On Tue, Feb 07, 2023 at 10:40:20AM +0000, Lucas Tanure wrote:
>> Shared boost allows two amplifiers to share a single boost
>> circuit by communicating on the MDSYNC bus.
>> The passive amplifier does not control the boost and receives
>> data from the active amplifier.
>>
>> Shared Boost is not supported in HDA Systems.
>>
> 
> Probably would be nice to put at least a note to say based on
> David's patches.
ack
> 
>> +static const struct reg_sequence cs35l41_shd_boost_seq[] = {
>> +	{CS35L41_PWR_CTRL3,	0x01000110},
> 
> This will blat whatever the user set in the DRE switch.
> Technically blats the CLASS H enable from the DAPM widget too,
> but as that always turns on should be a no-op. Probably should
> either not register the DRE switch or have setting it return an
> error for these boost modes.
Fixed in v2.
Changed to regmap_update_bits.
> 
>> +int cs35l41_global_enable(struct regmap *regmap, enum cs35l41_boost_type b_type, int enable,
>> +			  struct completion *pll_lock)
>>   {
>>   	int ret;
>> +	unsigned int gpio1;
>>   
>>   	switch (b_type) {
>> +	case CS35L41_SHD_BOOST_ACTV:
>> +	case CS35L41_SHD_BOOST_PASS:
>> +		regmap_update_bits(regmap, CS35L41_PWR_CTRL3, CS35L41_SYNC_EN_MASK, 0);
>> +
>> +		gpio1 = enable ? CS35L41_GPIO1_MDSYNC : CS35L41_GPIO1_HIZ;
>> +		regmap_update_bits(regmap, CS35L41_GPIO_PAD_CONTROL, CS35L41_GPIO1_CTRL_MASK,
>> +				   gpio1 << CS35L41_GPIO1_CTRL_SHIFT);
>> +
>> +		ret = regmap_update_bits(regmap, CS35L41_PWR_CTRL1, CS35L41_GLOBAL_EN_MASK,
>> +					 enable << CS35L41_GLOBAL_EN_SHIFT);
>> +		usleep_range(3000, 3100);
>> +		if (!enable)
>> +			break;
>> +
>> +		if (!pll_lock)
>> +			return -EINVAL;
>> +
>> +		ret = wait_for_completion_timeout(pll_lock, msecs_to_jiffies(1000));
>> +		if (ret == 0)
>> +			ret = -ETIMEDOUT;
> 
> This feels kinda scary, in that you are relying on a 1 to 1
> correspondence between this code running and getting a PLL lock
> signal. The datasheet is helpfully completely vague on when PLL
> locks are triggered.
> 
> The PLL enable seems to be set through set_sysclk, which could
> be called multiple times, per DAPM power up.  Does the PLL
> lock only go once global enable has been set? Can't help
> but wonder if a reinit_completion should probably go somewhere
> to ensure we are getting this lock of the PLL not a past one.
Added a reinit_completion at cs35l41_pcm_startup

> 
>> @@ -483,6 +483,11 @@ static irqreturn_t cs35l41_irq(int irq, void *data)
>>   		ret = IRQ_HANDLED;
>>   	}
>>   
>> +	if (status[2] & CS35L41_PLL_LOCK) {
>> +		regmap_write(cs35l41->regmap, CS35L41_IRQ1_STATUS3, CS35L41_PLL_LOCK);
>> +		complete(&cs35l41->pll_lock);
>> +	}
>> +
> 
> If you fall into any of the error cases in this IRQ handler above
> this, it will blat values you don't want into BST_EN although, to
> be fair that does look currently broken for external boost as
> well.
Fixed with a new patch in v2 series.

> 
> Thanks,
> Charles
>