drm/msm: gpu: Enable zap shader for A5XX

The A5XX GPU powers on in "secure" mode. In secure mode the GPU can
only render to buffers that are marked as secure and inaccessible
to the kernel and user through a series of hardware protections. In
practice secure mode is used to draw things like a UI on a secure
video frame.

In order to switch out of secure mode the GPU executes a special
shader that clears out the GMEM and other sensitve registers and
then writes a register. Because the kernel can't be trusted the
shader binary is signed and verified and programmed by the
secure world. To do this we need to read the MDT header and the
segments from the firmware location and put them in memory and
present them for approval.

For targets without secure support there is an out: if the
secure world doesn't support secure then there are no hardware
protections and we can freely write the SECVID_TRUST register from
the CPU. We don't have 100% confidence that we can query the
secure capabilities at run time but we have enough calls that
need to go right to give us some confidence that we're at least doing
something useful.

Of course if we guess wrong you trigger a permissions violation
which usually ends up in a system crash but thats a problem
that shows up immediately.

[v2: use child device per Bjorn]
[v3: use generic MDT loader per Bjorn]
[v4: use managed dma functions and ifdefs for the MDT loader]
[v5: Add depends for QCOM_MDT_LOADER]
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
[robclark: fix Kconfig to use select instead of depends + #if IS_ENABLED()]
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/Kconfig

@@ -5,6 +5,7 @@ config DRM_MSM
 	depends on ARCH_QCOM || (ARM && COMPILE_TEST)
 	depends on OF && COMMON_CLK
 	depends on MMU
+	select QCOM_MDT_LOADER
 	select REGULATOR
 	select DRM_KMS_HELPER
 	select DRM_PANEL

drivers/gpu/drm/msm/adreno/a5xx_gpu.c

@@ -11,6 +11,12 @@
  *
  */
 
+#include <linux/types.h>
+#include <linux/cpumask.h>
+#include <linux/qcom_scm.h>
+#include <linux/dma-mapping.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/soc/qcom/mdt_loader.h>
 #include "msm_gem.h"
 #include "msm_mmu.h"
 #include "a5xx_gpu.h"
@@ -18,6 +24,62 @@
 extern bool hang_debug;
 static void a5xx_dump(struct msm_gpu *gpu);
 
+#define GPU_PAS_ID 13
+
+#if IS_ENABLED(CONFIG_QCOM_MDT_LOADER)
+
+static int zap_shader_load_mdt(struct device *dev, const char *fwname)
+{
+	const struct firmware *fw;
+	phys_addr_t mem_phys;
+	ssize_t mem_size;
+	void *mem_region = NULL;
+	int ret;
+
+	/* Request the MDT file for the firmware */
+	ret = request_firmware(&fw, fwname, dev);
+	if (ret) {
+		DRM_DEV_ERROR(dev, "Unable to load %s\n", fwname);
+		return ret;
+	}
+
+	/* Figure out how much memory we need */
+	mem_size = qcom_mdt_get_size(fw);
+	if (mem_size < 0) {
+		ret = mem_size;
+		goto out;
+	}
+
+	/* Allocate memory for the firmware image */
+	mem_region = dmam_alloc_coherent(dev, mem_size, &mem_phys, GFP_KERNEL);
+	if (!mem_region) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* Load the rest of the MDT */
+	ret = qcom_mdt_load(dev, fw, fwname, GPU_PAS_ID, mem_region, mem_phys,
+		mem_size);
+	if (ret)
+		goto out;
+
+	/* Send the image to the secure world */
+	ret = qcom_scm_pas_auth_and_reset(GPU_PAS_ID);
+	if (ret)
+		DRM_DEV_ERROR(dev, "Unable to authorize the image\n");
+
+out:
+	release_firmware(fw);
+
+	return ret;
+}
+#else
+static int zap_shader_load_mdt(struct device *dev, const char *fwname)
+{
+	return -ENODEV;
+}
+#endif
+
 static void a5xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit,
 	struct msm_file_private *ctx)
 {
@@ -304,6 +366,98 @@ static int a5xx_ucode_init(struct msm_gpu *gpu)
 	return 0;
 }
 
+#define SCM_GPU_ZAP_SHADER_RESUME 0
+
+static int a5xx_zap_shader_resume(struct msm_gpu *gpu)
+{
+	int ret;
+
+	ret = qcom_scm_set_remote_state(SCM_GPU_ZAP_SHADER_RESUME, GPU_PAS_ID);
+	if (ret)
+		DRM_ERROR("%s: zap-shader resume failed: %d\n",
+			gpu->name, ret);
+
+	return ret;
+}
+
+/* Set up a child device to "own" the zap shader */
+static int a5xx_zap_shader_dev_init(struct device *parent, struct device *dev)
+{
+	struct device_node *node;
+	int ret;
+
+	if (dev->parent)
+		return 0;
+
+	/* Find the sub-node for the zap shader */
+	node = of_get_child_by_name(parent->of_node, "zap-shader");
+	if (!node) {
+		DRM_DEV_ERROR(parent, "zap-shader not found in device tree\n");
+		return -ENODEV;
+	}
+
+	dev->parent = parent;
+	dev->of_node = node;
+	dev_set_name(dev, "adreno_zap_shader");
+
+	ret = device_register(dev);
+	if (ret) {
+		DRM_DEV_ERROR(parent, "Couldn't register zap shader device\n");
+		goto out;
+	}
+
+	ret = of_reserved_mem_device_init(dev);
+	if (ret) {
+		DRM_DEV_ERROR(parent, "Unable to set up the reserved memory\n");
+		device_unregister(dev);
+	}
+
+out:
+	if (ret)
+		dev->parent = NULL;
+
+	return ret;
+}
+
+static int a5xx_zap_shader_init(struct msm_gpu *gpu)
+{
+	static bool loaded;
+	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
+	struct a5xx_gpu *a5xx_gpu = to_a5xx_gpu(adreno_gpu);
+	struct platform_device *pdev = a5xx_gpu->pdev;
+	int ret;
+
+	/*
+	 * If the zap shader is already loaded into memory we just need to kick
+	 * the remote processor to reinitialize it
+	 */
+	if (loaded)
+		return a5xx_zap_shader_resume(gpu);
+
+	/* We need SCM to be able to load the firmware */
+	if (!qcom_scm_is_available()) {
+		DRM_DEV_ERROR(&pdev->dev, "SCM is not available\n");
+		return -EPROBE_DEFER;
+	}
+
+	/* Each GPU has a target specific zap shader firmware name to use */
+	if (!adreno_gpu->info->zapfw) {
+		DRM_DEV_ERROR(&pdev->dev,
+			"Zap shader firmware file not specified for this target\n");
+		return -ENODEV;
+	}
+
+	ret = a5xx_zap_shader_dev_init(&pdev->dev, &a5xx_gpu->zap_dev);
+
+	if (!ret)
+		ret = zap_shader_load_mdt(&a5xx_gpu->zap_dev,
+			adreno_gpu->info->zapfw);
+
+	loaded = !ret;
+
+	return ret;
+}
+
 #define A5XX_INT_MASK (A5XX_RBBM_INT_0_MASK_RBBM_AHB_ERROR | \
 	  A5XX_RBBM_INT_0_MASK_RBBM_TRANSFER_TIMEOUT | \
 	  A5XX_RBBM_INT_0_MASK_RBBM_ME_MS_TIMEOUT | \
@@ -488,8 +642,27 @@ static int a5xx_hw_init(struct msm_gpu *gpu)
 			return -EINVAL;
 	}
 
-	/* Put the GPU into unsecure mode */
+	/*
+	 * Try to load a zap shader into the secure world. If successful
+	 * we can use the CP to switch out of secure mode. If not then we
+	 * have no resource but to try to switch ourselves out manually. If we
+	 * guessed wrong then access to the RBBM_SECVID_TRUST_CNTL register will
+	 * be blocked and a permissions violation will soon follow.
+	 */
+	ret = a5xx_zap_shader_init(gpu);
+	if (!ret) {
+		OUT_PKT7(gpu->rb, CP_SET_SECURE_MODE, 1);
+		OUT_RING(gpu->rb, 0x00000000);
+
+		gpu->funcs->flush(gpu);
+		if (!gpu->funcs->idle(gpu))
+			return -EINVAL;
+	} else {
+		/* Print a warning so if we die, we know why */
+		dev_warn_once(gpu->dev->dev,
+			"Zap shader not enabled - using SECVID_TRUST_CNTL instead\n");
 		gpu_write(gpu, REG_A5XX_RBBM_SECVID_TRUST_CNTL, 0x0);
+	}
 
 	return 0;
 }
@@ -521,6 +694,9 @@ static void a5xx_destroy(struct msm_gpu *gpu)
 
 	DBG("%s", gpu->name);
 
+	if (a5xx_gpu->zap_dev.parent)
+		device_unregister(&a5xx_gpu->zap_dev);
+
 	if (a5xx_gpu->pm4_bo) {
 		if (a5xx_gpu->pm4_iova)
 			msm_gem_put_iova(a5xx_gpu->pm4_bo, gpu->id);

drivers/gpu/drm/msm/adreno/a5xx_gpu.h

@@ -36,6 +36,8 @@ struct a5xx_gpu {
 	uint32_t gpmu_dwords;
 
 	uint32_t lm_leakage;
+
+	struct device zap_dev;
 };
 
 #define to_a5xx_gpu(x) container_of(x, struct a5xx_gpu, base)

drivers/gpu/drm/msm/adreno/adreno_device.c

@@ -86,6 +86,7 @@ static const struct adreno_info gpulist[] = {
 			ADRENO_QUIRK_FAULT_DETECT_MASK,
 		.init = a5xx_gpu_init,
 		.gpmufw = "a530v3_gpmu.fw2",
+		.zapfw = "a530_zap.mdt",
 	},
 };
 

drivers/gpu/drm/msm/adreno/adreno_gpu.h

@@ -77,6 +77,7 @@ struct adreno_info {
 	uint32_t gmem;
 	enum adreno_quirks quirks;
 	struct msm_gpu *(*init)(struct drm_device *dev);
+	const char *zapfw;
 };
 
 const struct adreno_info *adreno_info(struct adreno_rev rev);