Re: [PATCH v4 1/1] regmap: Synchronize cache for the page selector

[Andy Shevchenko]

On Wed, Feb 18, 2026 at 09:30:41AM +0100, Marek Szyprowski wrote:
> On 18.02.2026 08:46, Andy Shevchenko wrote:
> > If the selector register is represented in each page, its value
> > according to the debugfs is stale because it gets synchronized
> > only after the real page switch happens. Hence the regmap cache
> > initialisation from the HW inherits outdated data in the selector
> > register.
> >
> > Synchronize cache for the page selector just in time.
> >
> > Before (offset followed by hexdump, the first byte is selector):
> >
> >      // Real registers
> >      18: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
> >      ...
> >      // Virtual (per port)
> >      40: 05 ff 00 00 e0 e0 00 00 00 00 00 1f
> >      50: 00 ff 00 00 e0 e0 00 00 00 00 00 1f
> >      60: 01 ff 00 00 ff ff 00 00 00 00 00 00
> >      70: 02 ff 00 00 cf f3 00 00 00 00 00 0c
> >      80: 03 ff 00 00 00 00 00 00 00 00 00 ff
> >      90: 04 ff 00 00 ff 0f 00 00 f0 00 00 00
> >
> > After:
> >
> >      // Real registers
> >      18: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
> >      ...
> >      // Virtual (per port)
> >      40: 00 ff 00 00 e0 e0 00 00 00 00 00 1f
> >      50: 01 ff 00 00 e0 e0 00 00 00 00 00 1f
> >      60: 02 ff 00 00 ff ff 00 00 00 00 00 00
> >      70: 03 ff 00 00 cf f3 00 00 00 00 00 0c
> >      80: 04 ff 00 00 00 00 00 00 00 00 00 ff
> >      90: 05 ff 00 00 ff 0f 00 00 f0 00 00 00
> >
> > Fixes: 6863ca622759 ("regmap: Add support for register indirect addressing.")
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > ---
> > v4: reworked the approach completely
> >
> > Marek, Dmitry,
> > Please, test on your HW to be sure this will have no side effects
> > in your case with LT9611.
> 
> It looks that it ends in infinite recurrent calls after this patch:

Thank you for the prompt testing! Can you also _add_ the patch on top from
https://lore.kernel.org/all/Z4ppo8wV3nicOfAQ@xxxxxxxxxxxxxxxxxx/ ?

> Insufficient stack space to handle exception!
> ESR: 0x0000000096000047 -- DABT (current EL)
> FAR: 0xffff8000859bffe0
> Task stack:     [0xffff8000859c0000..0xffff8000859c4000]
> IRQ stack:      [0xffff800080030000..0xffff800080034000]
> Overflow stack: [0xffff0001fef36140..0xffff0001fef37140]
> CPU: 6 UID: 0 PID: 341 Comm: (udev-worker) Not tainted 
> 6.19.0-next-20260217+ #12215 PREEMPT
> Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : _regmap_select_page+0x4/0x120
> lr : _regmap_raw_read+0x240/0x340

-- 
With Best Regards,
Andy Shevchenko