[PATCH v3] pmdomain: imx: gpcv2: Add delay after power up handshake

[Adam Ford]

On Fri, May 10, 2024 at 10:15 PM Shengjiu Wang <shengjiu.wang at nxp.com> wrote:
>
> AudioMix BLK-CTRL on i.MX8MP encountered an accessing register issue
> after power up.
>
> [    2.181035] Kernel panic - not syncing: Asynchronous SError Interrupt
> [    2.181038] CPU: 1 PID: 48 Comm: kworker/u16:2 Not tainted 6.9.0-rc5-next-20240424-00003-g21cec88845c6 #171
> [    2.181047] Hardware name: NXP i.MX8MPlus EVK board (DT)
> [    2.181050] Workqueue: events_unbound deferred_probe_work_func
> [    2.181064] Call trace:
> [...]
> [    2.181142]  arm64_serror_panic+0x6c/0x78
> [    2.181149]  do_serror+0x3c/0x70
> [    2.181157]  el1h_64_error_handler+0x30/0x48
> [    2.181164]  el1h_64_error+0x64/0x68
> [    2.181171]  clk_imx8mp_audiomix_runtime_resume+0x34/0x44
> [    2.181183]  __genpd_runtime_resume+0x30/0x80
> [    2.181195]  genpd_runtime_resume+0x110/0x244
> [    2.181205]  __rpm_callback+0x48/0x1d8
> [    2.181213]  rpm_callback+0x68/0x74
> [    2.181224]  rpm_resume+0x468/0x6c0
> [    2.181234]  __pm_runtime_resume+0x50/0x94
> [    2.181243]  pm_runtime_get_suppliers+0x60/0x8c
> [    2.181258]  __driver_probe_device+0x48/0x12c
> [    2.181268]  driver_probe_device+0xd8/0x15c
> [    2.181278]  __device_attach_driver+0xb8/0x134
> [    2.181290]  bus_for_each_drv+0x84/0xe0
> [    2.181302]  __device_attach+0x9c/0x188
> [    2.181312]  device_initial_probe+0x14/0x20
> [    2.181323]  bus_probe_device+0xac/0xb0
> [    2.181334]  deferred_probe_work_func+0x88/0xc0
> [    2.181344]  process_one_work+0x150/0x290
> [    2.181357]  worker_thread+0x2f8/0x408
> [    2.181370]  kthread+0x110/0x114
> [    2.181381]  ret_from_fork+0x10/0x20
> [    2.181391] SMP: stopping secondary CPUs
>

The imx8mp-beacon board suffers from this as well, and I can confirm
the patch also fixes it.  It might be a coincidence, but the etnaviv
NPU also enumerates more reliably now too.

adam

> According to comments in power up handshake:
>
>         /* request the ADB400 to power up */
>         if (domain->bits.hskreq) {
>                 regmap_update_bits(domain->regmap, domain->regs->hsk,
>                                    domain->bits.hskreq, domain->bits.hskreq);
>
>                 /*
>                  * ret = regmap_read_poll_timeout(domain->regmap, domain->regs->hsk, reg_val,
>                  *                                (reg_val & domain->bits.hskack), 0,
>                  *                                USEC_PER_MSEC);
>                  * Technically we need the commented code to wait handshake. But that needs
>                  * the BLK-CTL module BUS clk-en bit being set.
>                  *
>                  * There is a separate BLK-CTL module and we will have such a driver for it,
>                  * that driver will set the BUS clk-en bit and handshake will be triggered
>                  * automatically there. Just add a delay and suppose the handshake finish
>                  * after that.
>                  */
>         }
>
> The BLK-CTL module needs to add delay to wait for a handshake request finished.
> For some BLK-CTL module (eg. AudioMix on i.MX8MP) doesn't have BUS clk-en
> bit, it is better to add delay in this driver, as the BLK-CTL module doesn't
> need to care about how it is powered up.
>
> regmap_read_bypassed() is to make sure the above write IO transaction already
> reaches target before udelay().
>
> Fixes: 1496dd413b2e ("clk: imx: imx8mp: Add pm_runtime support for power saving")
> Reported-by: Francesco Dolcini <francesco at dolcini.it>
> Closes: https://lore.kernel.org/all/66293535.170a0220.21fe.a2e7@mx.google.com/
> Suggested-by: Frank Li <frank.li at nxp.com>
> Signed-off-by: Shengjiu Wang <shengjiu.wang at nxp.com>

Tested-by:  Adam Ford <aford173 at gmail.com>

> ---
> changes in v3:
> - move change to gpcv2.c, as it is more reasonable to let power driver
>   to handle such power issue, suggested by Frank Li
>
> changes in v2:
> - reduce size of panic log in commit message
>
>  drivers/pmdomain/imx/gpcv2.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/pmdomain/imx/gpcv2.c b/drivers/pmdomain/imx/gpcv2.c
> index 4b828d74a606..856eaac0ec14 100644
> --- a/drivers/pmdomain/imx/gpcv2.c
> +++ b/drivers/pmdomain/imx/gpcv2.c
> @@ -393,6 +393,17 @@ static int imx_pgc_power_up(struct generic_pm_domain *genpd)
>                  * automatically there. Just add a delay and suppose the handshake finish
>                  * after that.
>                  */
> +
> +               /*
> +                * For some BLK-CTL module (eg. AudioMix on i.MX8MP) doesn't have BUS
> +                * clk-en bit, it is better to add delay here, as the BLK-CTL module
> +                * doesn't need to care about how it is powered up.
> +                *
> +                * regmap_read_bypassed() is to make sure the above write IO transaction
> +                * already reaches target before udelay()
> +                */
> +               regmap_read_bypassed(domain->regmap, domain->regs->hsk, &reg_val);
> +               udelay(5);
>         }
>
>         /* Disable reset clocks for all devices in the domain */
> --
> 2.34.1
>
>