linux-kernel - [PATCH 2/8] bus: fsl-mc: handle DMA config deferral in ACPI case

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Date:   Thu, 15 Jul 2021 17:07:12 +0300
From:   laurentiu.tudor@....com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Cc:     diana.craciun@....com, ioana.ciornei@....com, jon@...id-run.com,
        leoyang.li@....com, Laurentiu Tudor <laurentiu.tudor@....com>
Subject: [PATCH 2/8] bus: fsl-mc: handle DMA config deferral in ACPI case

From: Laurentiu Tudor <laurentiu.tudor@....com>

ACPI DMA configure API may return a defer status code, so handle it.
On top of this, move the MC firmware resume after the DMA setup
is completed to avoid crashing due to DMA setup not being done yet or
being deferred.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
---
 drivers/bus/fsl-mc/fsl-mc-bus.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index ffec838450f3..ffd7a1ff957a 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -1089,17 +1089,6 @@ static int fsl_mc_bus_probe(struct platform_device *pdev)
 	}
 
 	if (mc->fsl_mc_regs) {
-		/*
-		 * Some bootloaders pause the MC firmware before booting the
-		 * kernel so that MC will not cause faults as soon as the
-		 * SMMU probes due to the fact that there's no configuration
-		 * in place for MC.
-		 * At this point MC should have all its SMMU setup done so make
-		 * sure it is resumed.
-		 */
-		writel(readl(mc->fsl_mc_regs + FSL_MC_GCR1) & (~GCR1_P1_STOP),
-		       mc->fsl_mc_regs + FSL_MC_GCR1);
-
 		if (IS_ENABLED(CONFIG_ACPI) && !dev_of_node(&pdev->dev)) {
 			mc_stream_id = readl(mc->fsl_mc_regs + FSL_MC_FAPR);
 			/*
@@ -1113,11 +1102,24 @@ static int fsl_mc_bus_probe(struct platform_device *pdev)
 			error = acpi_dma_configure_id(&pdev->dev,
 						      DEV_DMA_COHERENT,
 						      &mc_stream_id);
+			if (error == -EPROBE_DEFER)
+				return error;
 			if (error)
 				dev_warn(&pdev->dev,
 					 "failed to configure dma: %d.\n",
 					 error);
 		}
+
+		/*
+		 * Some bootloaders pause the MC firmware before booting the
+		 * kernel so that MC will not cause faults as soon as the
+		 * SMMU probes due to the fact that there's no configuration
+		 * in place for MC.
+		 * At this point MC should have all its SMMU setup done so make
+		 * sure it is resumed.
+		 */
+		writel(readl(mc->fsl_mc_regs + FSL_MC_GCR1) & (~GCR1_P1_STOP),
+		       mc->fsl_mc_regs + FSL_MC_GCR1);
 	}
 
 	/*
-- 
2.17.1