linux-kernel - Re: [REGRESSION] OCTEON MMC driver failure with v4.19

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Date:   Tue, 6 Nov 2018 00:06:32 +0200
From:   Aaro Koskinen <aaro.koskinen@....fi>
To:     Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>, Rob Herring <robh@...nel.org>,
        Paul Burton <paul.burton@...s.com>, linux-mips@...ux-mips.org,
        linux-kernel@...r.kernel.org
Subject: Re: [REGRESSION] OCTEON MMC driver failure with v4.19

Hi,

On Fri, Oct 26, 2018 at 11:54:23PM +0300, Aaro Koskinen wrote:
> OCTEON (MIPS64) MMC driver probe fails with v4.19, because with
> 
> commit 6c2fb2ea76361da9b420a8e23a2a19e7842cbdda
> Author: Robin Murphy <robin.murphy@....com>
> Date:   Mon Jul 23 23:16:09 2018 +0100
> 
>     of/device: Set bus DMA mask as appropriate
> 
> we now get a default 32-bit bus DMA mask, and the device itself has
> 64-bit mask, so it gets rejected.
> 
> With the current mainline, the driver is again working (probably
> because of b4ebe6063204 ("dma-direct: implement complete bus_dma_mask
> handling")). But I think this is just because I happen to have < 4 GB RAM,
> and it probably could still fail on bigger systems..?

With the below change, the MMC card probe seems to with v4.19. But it
feels a bit hackish, don't you think... Is there some obvious simple
fix that I'm missing? Any comments?

diff --git a/arch/mips/cavium-octeon/octeon-platform.c b/arch/mips/cavium-octeon/octeon-platform.c
index 807cadaf554e..31fab09fadcc 100644
--- a/arch/mips/cavium-octeon/octeon-platform.c
+++ b/arch/mips/cavium-octeon/octeon-platform.c
@@ -1067,8 +1067,29 @@ int __init octeon_prune_device_tree(void)
 	return 0;
 }
 
+static int octeon_device_notifier_call(struct notifier_block *nb,
+				       unsigned long event, void *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+
+	if (event != BUS_NOTIFY_ADD_DEVICE ||
+	    !pdev || !pdev->dev.dma_mask || !pdev->dev.of_node)
+		return NOTIFY_DONE;
+
+	if (of_device_is_compatible(pdev->dev.of_node,
+				     "cavium,octeon-6130-mmc"))
+		*pdev->dev.dma_mask = DMA_BIT_MASK(64);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block platform_nb = {
+	.notifier_call = octeon_device_notifier_call,
+};
+
 static int __init octeon_publish_devices(void)
 {
+	bus_register_notifier(&platform_bus_type, &platform_nb);
 	return of_platform_populate(NULL, octeon_ids, NULL, NULL);
 }
 arch_initcall(octeon_publish_devices);

A.