[PATCH v2] soc: mediatek: mtk-infracfg: Disable ACP on MT8192

[Alyssa Rosenzweig]

MT8192 contains an experimental Accelerator Coherency Port
implementation, which does not work correctly but was unintentionally
enabled by default. For correct operation of the GPU, we must set a
chicken bit disabling ACP on MT8192.

Adapted from the following downstream change to the out-of-tree, legacy
Mali GPU driver:

https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2781271/5

Note this change is required for both Panfrost and the legacy kernel
driver.

v2: Move the change from clk-mt8192.c to mtk-infracfg.c (Robin).
Although it does not make sense to add this platform-specific hack to
the GPU driver, it has nothing to do with clocks. We already have
mtk-infracfg.c to manage other infracfg bits; the ACP disable should
live there too.

Co-developed-by: Robin Murphy <robin.murphy at arm.com>
Signed-off-by: Robin Murphy <robin.murphy at arm.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Cc: Nick Fan <Nick.Fan at mediatek.com>
Cc: Nicolas Boichat <drinkcat at chromium.org>
Cc: Chen-Yu Tsai <wenst at chromium.org>
Cc: Stephen Boyd <sboyd at kernel.org>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
---
 drivers/soc/mediatek/mtk-infracfg.c   | 19 +++++++++++++++++++
 include/linux/soc/mediatek/infracfg.h |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/drivers/soc/mediatek/mtk-infracfg.c b/drivers/soc/mediatek/mtk-infracfg.c
index 0590b68e0d78..2acf19676af2 100644
--- a/drivers/soc/mediatek/mtk-infracfg.c
+++ b/drivers/soc/mediatek/mtk-infracfg.c
@@ -6,6 +6,7 @@
 #include <linux/export.h>
 #include <linux/jiffies.h>
 #include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
 #include <linux/soc/mediatek/infracfg.h>
 #include <asm/processor.h>
 
@@ -72,3 +73,21 @@ int mtk_infracfg_clear_bus_protection(struct regmap *infracfg, u32 mask,
 
 	return ret;
 }
+
+static int __init mtk_infracfg_init(void)
+{
+	struct regmap *infracfg;
+
+	/*
+	 * MT8192 has an experimental path to route GPU traffic to the DSU's
+	 * Accelerator Coherency Port, which is inadvertently enabled by
+	 * default. It turns out not to work, so disable it to prevent spurious
+	 * GPU faults.
+	 */
+	infracfg = syscon_regmap_lookup_by_compatible("mediatek,mt8192-infracfg");
+	if (!IS_ERR(infracfg))
+		regmap_set_bits(infracfg, MT8192_INFRA_CTRL,
+				MT8192_INFRA_CTRL_DISABLE_MFG2ACP);
+	return 0;
+}
+postcore_initcall(mtk_infracfg_init);
diff --git a/include/linux/soc/mediatek/infracfg.h b/include/linux/soc/mediatek/infracfg.h
index d858e0bab7a2..fcbbd0dd5e55 100644
--- a/include/linux/soc/mediatek/infracfg.h
+++ b/include/linux/soc/mediatek/infracfg.h
@@ -229,6 +229,9 @@
 #define INFRA_TOPAXI_PROTECTEN_SET		0x0260
 #define INFRA_TOPAXI_PROTECTEN_CLR		0x0264
 
+#define MT8192_INFRA_CTRL			0x290
+#define MT8192_INFRA_CTRL_DISABLE_MFG2ACP	BIT(9)
+
 #define REG_INFRA_MISC				0xf00
 #define F_DDR_4GB_SUPPORT_EN			BIT(13)
 
-- 
2.34.1