imx_dsp_rproc: Use reset controller API to control the DSP

DSP on i.MX8MP doesn't have a direct reset line so according to hardware
design team in order to handle assert/deassert/reset functionality we
need to use a combination of control bits from two modules. Audio block
control module for Run/Stall control of the DSP and DAP module in order
to do software reset.

In a first step, for i.MX8MP we are switching on using the reset
controller API to handle the DSP Run/Stall bits i.MX8MP. This comes with
the advantage of offering a better probe ordering and a more natural way
of abstracting the Audio block control bits.

Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20250311085812.1296243-9-daniel.baluta@nxp.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

Author: dbaluta

drivers/remoteproc/imx_dsp_rproc.c

@@ -19,6 +19,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/remoteproc.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 
 #include "imx_rproc.h"
@@ -111,6 +112,7 @@ enum imx_dsp_rp_mbox_messages {
  */
 struct imx_dsp_rproc {
 	struct regmap				*regmap;
+	struct reset_control			*run_stall;
 	struct rproc				*rproc;
 	const struct imx_dsp_rproc_dcfg		*dsp_dcfg;
 	struct clk_bulk_data			clks[DSP_RPROC_CLK_MAX];
@@ -192,9 +194,7 @@ static int imx8mp_dsp_reset(struct imx_dsp_rproc *priv)
 	/* Keep reset asserted for 10 cycles */
 	usleep_range(1, 2);
 
-	regmap_update_bits(priv->regmap, IMX8M_AudioDSP_REG2,
-			   IMX8M_AudioDSP_REG2_RUNSTALL,
-			   IMX8M_AudioDSP_REG2_RUNSTALL);
+	reset_control_assert(priv->run_stall);
 
 	/* Take the DSP out of reset and keep stalled for FW loading */
 	pwrctl = readl(dap + IMX8M_DAP_PWRCTL);
@@ -231,13 +231,9 @@ static int imx8ulp_dsp_reset(struct imx_dsp_rproc *priv)
 
 /* Specific configuration for i.MX8MP */
 static const struct imx_rproc_dcfg dsp_rproc_cfg_imx8mp = {
-	.src_reg	= IMX8M_AudioDSP_REG2,
-	.src_mask	= IMX8M_AudioDSP_REG2_RUNSTALL,
-	.src_start	= 0,
-	.src_stop	= IMX8M_AudioDSP_REG2_RUNSTALL,
 	.att		= imx_dsp_rproc_att_imx8mp,
 	.att_size	= ARRAY_SIZE(imx_dsp_rproc_att_imx8mp),
-	.method		= IMX_RPROC_MMIO,
+	.method		= IMX_RPROC_RESET_CONTROLLER,
 };
 
 static const struct imx_dsp_rproc_dcfg imx_dsp_rproc_cfg_imx8mp = {
@@ -329,6 +325,9 @@ static int imx_dsp_rproc_start(struct rproc *rproc)
 					  true,
 					  rproc->bootaddr);
 		break;
+	case IMX_RPROC_RESET_CONTROLLER:
+		ret = reset_control_deassert(priv->run_stall);
+		break;
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -369,6 +368,9 @@ static int imx_dsp_rproc_stop(struct rproc *rproc)
 					  false,
 					  rproc->bootaddr);
 		break;
+	case IMX_RPROC_RESET_CONTROLLER:
+		ret = reset_control_assert(priv->run_stall);
+		break;
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -995,6 +997,13 @@ static int imx_dsp_rproc_detect_mode(struct imx_dsp_rproc *priv)
 
 		priv->regmap = regmap;
 		break;
+	case IMX_RPROC_RESET_CONTROLLER:
+		priv->run_stall = devm_reset_control_get_exclusive(dev, "runstall");
+		if (IS_ERR(priv->run_stall)) {
+			dev_err(dev, "Failed to get DSP runstall reset control\n");
+			return PTR_ERR(priv->run_stall);
+		}
+		break;
 	default:
 		ret = -EOPNOTSUPP;
 		break;

drivers/remoteproc/imx_rproc.h

@@ -24,6 +24,8 @@ enum imx_rproc_method {
 	IMX_RPROC_SMC,
 	/* Through System Control Unit API */
 	IMX_RPROC_SCU_API,
+	/* Through Reset Controller API */
+	IMX_RPROC_RESET_CONTROLLER,
 };
 
 /* dcfg flags */