linux-kernel - [PATCH 3.2 105/153] drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE

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Date:   Wed, 30 May 2018 11:52:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Alex Deucher" <alexander.deucher@....com>,
        "Ben Crocker" <bcrocker@...hat.com>
Subject: [PATCH 3.2 105/153] drm/radeon: insist on 32-bit DMA for Cedar on
 PPC64/PPC64LE

3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Crocker <bcrocker@...hat.com>

commit 2c83029cda55a5e7665c7c6326909427d6a01350 upstream.

In radeon_device_init, set the need_dma32 flag for Cedar chips
(e.g. FirePro 2270).  This fixes, or at least works around, a bug
on PowerPC exposed by last year's commits

8e3f1b1d8255105f31556aacf8aeb6071b00d469 (Russell Currey)

and

253fd51e2f533552ae35a0c661705da6c4842c1b (Alistair Popple)

which enabled the 64-bit DMA iommu bypass.

This caused the device to freeze, in some cases unrecoverably, and is
the subject of several bug reports internal to Red Hat.

Signed-off-by: Ben Crocker <bcrocker@...hat.com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/radeon/radeon_device.c | 4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -784,6 +784,10 @@ int radeon_device_init(struct radeon_dev
 	if ((rdev->flags & RADEON_IS_PCI) &&
 	    (rdev->family <= CHIP_RS740))
 		rdev->need_dma32 = true;
+#ifdef CONFIG_PPC64
+	if (rdev->family == CHIP_CEDAR)
+		rdev->need_dma32 = true;
+#endif
 
 	dma_bits = rdev->need_dma32 ? 32 : 40;
 	r = pci_set_dma_mask(rdev->pdev, DMA_BIT_MASK(dma_bits));