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Date: Thu, 25 Apr 2024 16:49:42 -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] clk: imx: imx8mp: Add delay after power up
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On Thu, Apr 25, 2024 at 06:19:24PM +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 power domain.
> 
> Otherwise there is error:
> 
> [    2.180834] SError Interrupt on CPU1, code 0x00000000bf000002 -- SError
> [    2.180849] CPU: 1 PID: 48 Comm: kworker/u16:2 Not tainted 6.9.0-rc5-next-20240424-00003-g21cec88845c6 #171
> [    2.180856] Hardware name: NXP i.MX8MPlus EVK board (DT)
> [    2.180861] Workqueue: events_unbound deferred_probe_work_func
> [    2.180878] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [    2.180885] pc : clk_imx8mp_audiomix_runtime_resume+0x34/0x44
> [    2.180900] lr : pm_generic_runtime_resume+0x2c/0x44
> [    2.180910] sp : ffff800083423a20
> [    2.180913] x29: ffff800083423a20 x28: 0000000000000000 x27: 0000000000000000
> [    2.180922] x26: ffff0000c0e4e410 x25: 0000000000000000 x24: 0000000000000000
> [    2.180935] x23: 0000000000000000 x22: ffff0000c02afd20 x21: 0000000000000000
> [    2.180945] x20: ffff0000c162a000 x19: ffff0000c0e52810 x18: ffffffffffffffff
> [    2.180959] x17: 0000000000000000 x16: 0000000000000100 x15: ffff8000834239f0
> [    2.180970] x14: ffff0000c03d0a1c x13: ffff0000c0a03440 x12: 00000000000003c7
> [    2.180982] x11: 0000000000000000 x10: ffff8000825010ba x9 : 0000000000000008
> [    2.180993] x8 : 0000000000000008 x7 : 0000000000000000 x6 : 0000000000000000
> [    2.181005] x5 : ffff8000838b0000 x4 : ffff0000c0e66088 x3 : ffff8000813852c0
> [    2.181018] x2 : 0000000000000000 x1 : 0000000000000004 x0 : ffff8000838b0300
> [    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:
> [    2.181066]  dump_backtrace+0x90/0xe8
> [    2.181080]  show_stack+0x18/0x24
> [    2.181091]  dump_stack_lvl+0x34/0x8c
> [    2.181104]  dump_stack+0x18/0x24
> [    2.181117]  panic+0x39c/0x3d0
> [    2.181129]  nmi_panic+0x48/0x94
> [    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
> [    2.181400] Kernel Offset: disabled
> [    2.181403] CPU features: 0x0,00000040,00100000,4200421b
> [    2.181407] Memory Limit: none
> [    2.463040] ---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]---
> 
> 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>
> ---
>  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 e4231e9c8f05..cb44c460548e 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>
> @@ -362,6 +363,12 @@ 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);
> +

https://lore.kernel.org/imx/20230727152503.2199550-1-shenwei.wang@nxp.com/T/#m2dc5111e9628235f031c0bad2a137222b0205a61

supposed clk_imx8mp_audiomix_save_restore() is that write save data into
some registers.

See above link for detail, it may not delay 5us before write to register. 
You need 
	readl();
	udelay(5);
	writel();

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