imx8mp: add potential fix for pmdomain kernel panic in audiomix

linux/patches6.10/imx8mp-mnt-pocket-reform/20240810-v3-pmdomain-imx-gpcv2-Add-delay-after-power-up-handshake.patch

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+From: Shengjiu Wang <shengjiu.wang@nxp.com>
+To: ulf.hansson@linaro.org,
+	heiko@sntech.de,
+	u.kleine-koenig@pengutronix.de,
+	geert+renesas@glider.be,
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+Cc: linux-clk@vger.kernel.org,
+	linux-arm-kernel@lists.infradead.org,
+	linux-kernel@vger.kernel.org
+Subject: [PATCH v3] pmdomain: imx: gpcv2: Add delay after power up handshake
+Date: Sat, 11 May 2024 10:55:25 +0800
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+
+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
+
+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@dolcini.it>
+Closes: https://lore.kernel.org/all/66293535.170a0220.21fe.a2e7@mx.google.com/
+Suggested-by: Frank Li <frank.li@nxp.com>
+Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
+Tested-by:  Adam Ford <aford173@gmail.com>
+Tested-by: Alexander Stein <alexander.stein@ew.tq-group.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 */