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Date: Mon, 6 May 2024 14:21:43 -0400
From: Frank Li <Frank.li@nxp.com>
To: Shengjiu Wang <shengjiu.wang@nxp.com>
Cc: abelvesa@kernel.org, peng.fan@nxp.com, mturquette@baylibre.com,
	sboyd@kernel.org, shawnguo@kernel.org, s.hauer@pengutronix.de,
	kernel@pengutronix.de, festevam@gmail.com, imx@lists.linux.dev,
	shengjiu.wang@gmail.com, linux-clk@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] clk: imx: imx8mp: Add delay after power up
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On Mon, May 06, 2024 at 11:35:02AM +0800, Shengjiu Wang wrote:
> According to comments in drivers/pmdomain/imx/gpcv2.c:
> 
> 	/* 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
> before accessing registers, which is just after the enabling of the power domain.
> 
> Otherwise there is error:
> 
> [    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
> 
> Fixes: 1496dd413b2e ("clk: imx: imx8mp: Add pm_runtime support for power saving")
> Reported-by: Francesco Dolcini <francesco@dolcini.it>
> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> Revewied-by: Peng Fan <peng.fan@nxp.com>
> ---
> changes in v2:
> - reduce size of panic log in commit message
> 
>  drivers/clk/imx/clk-imx8mp-audiomix.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/clk/imx/clk-imx8mp-audiomix.c b/drivers/clk/imx/clk-imx8mp-audiomix.c
> index b381d6f784c8..ae2c0f254225 100644
> --- a/drivers/clk/imx/clk-imx8mp-audiomix.c
> +++ b/drivers/clk/imx/clk-imx8mp-audiomix.c
> @@ -6,6 +6,7 @@
>   */
>  
>  #include <linux/clk-provider.h>
> +#include <linux/delay.h>
>  #include <linux/device.h>
>  #include <linux/io.h>
>  #include <linux/mod_devicetable.h>
> @@ -360,6 +361,12 @@ static int clk_imx8mp_audiomix_runtime_suspend(struct device *dev)
>  
>  static int clk_imx8mp_audiomix_runtime_resume(struct device *dev)
>  {
> +	/*
> +	 * According to the drivers/pmdomain/imx/gpcv2.c
> +	 * need to wait for handshake request to propagate
> +	 */
> +	udelay(5);
> +

Did you address the issue I comments at v1?
It should not fix at here, I think it should be gpcv2.c to delay 5us.

Frank

>  	clk_imx8mp_audiomix_save_restore(dev, false);
>  
>  	return 0;
> -- 
> 2.34.1
>