On 9/5/23 21:11, Rhodes, David wrote:
On 9/5/23 5:29 AM, Charles Keepax wrote:
On Sun, Sep 03, 2023 at 12:06:16AM +0300, Cristian Ciocaltea wrote:
Enabling the active/passive shared boosts involves writing the MDSYNC UP register sequence, which cannot be performed before receiving the PLL lock signal.
Thanks for looking at this apologies this was missed in the initial review of the patch.
Thanks Cristian, I agree with the intent of your patch. We do not expect that clocks are always available before the DAPM PMU event and shared boost should still be configured if they are not.
+int cs35l41_mdsync_up(struct regmap *regmap) +{ + struct reg_sequence cs35l41_mdsync_up_seq[] = { + {CS35L41_PWR_CTRL3, 0}, + {CS35L41_PWR_CTRL1, 0x00000000, 3000}, + {CS35L41_PWR_CTRL1, 0x00000001, 3000}, + };
I don't know why PWR_CTRL1 is included in the up sequence here. This toggles GLOBAL_EN, which will cause the PLL to unlock and lock again. Doing this defeats the purpose of setting SYNC_EN in a separate operation, which is to only do so when the amp is powered on and has locked the PLL. GLOBAL_EN is set by the mdsync_down_seq, so all that is needed when the PLL is locked is to set SYNC_EN.
Unfortunately I had to rely on the existing implementation as I don't have access to the datasheet.
If I got it right, we should drop all write operations on PWR_CTRL1, and simply set the CS35L41_SYNC_EN_MASK bit in PWR_CTRL3.
Is this now safe? By pulling this out into a worker thread, it is no longer under the DAPM lock, which makes me worry this can race with the other uses of PWR_CTRL3 which could theoretically change state between when you read the reg and when you write it.
That's a good point, it should be fixed implicitly by replacing the read/write operations with a single regmap_update_bits() call, which is protected by regmap's internal lock.
The Class-H DAPM widget also uses the PWR_CTRL3 register.
One question I might also have would be does a worker thread make more sense or would it be simpler to do the mdsync power up directly in response to the PLL lock IRQ?
I agree with implementing this in the PLL lock IRQ. As I described above, all that would need to be done is to set SYNC_EN in the PLL Lock IRQ handler.
As a matter of fact I initially considered doing this in the IRQ handler, but I also wanted to understand the reasoning behind current solution. Therefore I searched the ML archive for any relevant review comments, and I came across [1] which raises some concerns regarding the PLL lock signal, e.g. lack of documentation regarding trigger time & frequency.
If going with the IRQ handler approach is still the recommended approach, I will handle it in v2.
Thanks for reviewing, Cristian
[1] https://lore.kernel.org/all/20230207114855.GC36097@ediswmail.ad.cirrus.com/