[1/2] drm/ast: Support reading configuration values

Commit Message

Benjamin Herrenschmidt Feb. 16, 2017, 9:09 a.m. UTC

From: Russell Currey <[e-mail]>

The ast driver configures a window to enable access into BMC memory space
in order to read some configuration registers.  If this window is
disabled, which it can be from the BMC side, the ast driver can't
function.  Closing this window is a necessity for security if a machine's
host side and BMC side are controlled by different parties; i.e. a cloud
provider offering machines "bare metal".

A recent patch from Aspeed tries to detect whether that window is
enabled and uses default values if not. Unfortunately this won't work
on systems such as POWER machines that have strong PCIe error handling
as the attempt at detection will cause a PCIe abort if the window is
closed.

To work around this, enable reading these configuration values from the
device tree instead of through the window into BMC memory if the
corresponding DT properties are available. If not, the driver defaults
to the existing test which i cleaned up a little bit.

Signed-off-by: Russell Currey <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>
--
v2. [BenH]
    - Reworked on top of Aspeed P2A patch
    - Cleanup overall detection via a "config_mode" and log the
      selected mode for diagnostics purposes
    - Add a property for the SCU straps
---
 drivers/gpu/drm/ast/ast_drv.h  |   6 +-
 drivers/gpu/drm/ast/ast_main.c | 208 ++++++++++++++++++++++++-----------------
 drivers/gpu/drm/ast/ast_post.c |   7 +-
 3 files changed, 127 insertions(+), 94 deletions(-)

Patch

diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_drv.h
index 7abda94..3bedcf7 100644
--- a/drivers/gpu/drm/ast/ast_drv.h
+++ b/drivers/gpu/drm/ast/ast_drv.h
@@ -113,7 +113,11 @@  struct ast_private {
 	struct ttm_bo_kmap_obj cache_kmap;
 	int next_cursor;
 	bool support_wide_screen;
-	bool DisableP2A;
+	enum {
+		ast_use_p2a,
+		ast_use_dt,
+		ast_use_defaults
+	} config_mode;
 
 	enum ast_tx_chip tx_chip_type;
 	u8 dp501_maxclk;
diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 533e762..d42a4f5 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -65,10 +65,43 @@  uint8_t ast_get_index_reg_mask(struct ast_private *ast,
 
 static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 {
+	struct device_node *np = dev->pdev->dev.of_node;
 	struct ast_private *ast = dev->dev_private;
-	uint32_t data, jreg;
+	uint32_t data, jreg, scu_rev;
 	ast_open_key(ast);
 
+
+	/* Check if we have device-tree properties */
+	if (np && !of_property_read_u32(np, "ast,scu-revision-id", &scu_rev)) {
+		/* We do, disable P2A access */
+		ast->config_mode = ast_use_dt;
+		DRM_INFO("Using device-tree for configuration\n");
+	} else {
+		/*
+		 * Check if P2A access works. This will trigger a PCIe abort
+		 * if it doesn't so it's not recommended on platforms where
+		 * this is a fatal error. Those should use the device-tree
+		 * or Aspeed should come up with a different mechanism.
+		 */
+		data = ast_read32(ast, 0xf004);
+		if (data == 0xFFFFFFFF) {
+			ast->config_mode = ast_use_defaults;
+			scu_rev = 0xffffffff;
+			DRM_INFO("P2A bridge disabled, using default"
+				 " configuration\n");
+		} else {
+			/* P2A works, grab silicon revision */
+			ast->config_mode = ast_use_p2a;
+
+			DRM_INFO("Using P2A bridge for configuration\n");
+
+			/* Read SCU7c (silicon revision register) */
+			ast_write32(ast, 0xf004, 0x1e6e0000);
+			ast_write32(ast, 0xf000, 0x1);
+			scu_rev = ast_read32(ast, 0x1207c);
+		}
+	}
+
 	if (dev->pdev->device == PCI_CHIP_AST1180) {
 		ast->chip = AST1100;
 		DRM_INFO("AST 1180 detected\n");
@@ -80,12 +113,7 @@  static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 			ast->chip = AST2300;
 			DRM_INFO("AST 2300 detected\n");
 		} else if (dev->pdev->revision >= 0x10) {
-			uint32_t data;
-			ast_write32(ast, 0xf004, 0x1e6e0000);
-			ast_write32(ast, 0xf000, 0x1);
-
-			data = ast_read32(ast, 0x1207c);
-			switch (data & 0x0300) {
+			switch (scu_rev & 0x0300) {
 			case 0x0200:
 				ast->chip = AST1100;
 				DRM_INFO("AST 1100 detected\n");
@@ -124,12 +152,6 @@  static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 	} else
 		*need_post = false;
 
-	/* Check P2A Access */
-	ast->DisableP2A = true;
-	data = ast_read32(ast, 0xf004);
-	if (data != 0xFFFFFFFF)
-		ast->DisableP2A = false;
-
 	/* Check if we support wide screen */
 	switch (ast->chip) {
 	case AST1180:
@@ -146,17 +168,12 @@  static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 			ast->support_wide_screen = true;
 		else {
 			ast->support_wide_screen = false;
-			if (ast->DisableP2A == false) {
-				/* Read SCU7c (silicon revision register) */
-				ast_write32(ast, 0xf004, 0x1e6e0000);
-				ast_write32(ast, 0xf000, 0x1);
-				data = ast_read32(ast, 0x1207c);
-				data &= 0x300;
-				if (ast->chip == AST2300 && data == 0x0) /* ast1300 */
-					ast->support_wide_screen = true;
-				if (ast->chip == AST2400 && data == 0x100) /* ast1400 */
-					ast->support_wide_screen = true;
-			}
+			if (ast->chip == AST2300 &&
+			    (scu_rev & 0x300) == 0x0) /* ast1300 */
+				ast->support_wide_screen = true;
+			if (ast->chip == AST2400 &&
+			    (scu_rev & 0x300) == 0x100) /* ast1400 */
+				ast->support_wide_screen = true;
 		}
 		break;
 	}
@@ -220,85 +237,100 @@  static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 
 static int ast_get_dram_info(struct drm_device *dev)
 {
+	struct device_node *np = dev->pdev->dev.of_node;
 	struct ast_private *ast = dev->dev_private;
-	uint32_t data, data2;
-	uint32_t denum, num, div, ref_pll;
+	uint32_t mcr_cfg, mcr_scu_mpll, mcr_scu_strap;
+	uint32_t denum, num, div, ref_pll, dsel;
 
-	if (ast->DisableP2A)
-	{
+	switch(ast->config_mode) {
+	case ast_use_defaults:
 		ast->dram_bus_width = 16;
 		ast->dram_type = AST_DRAM_1Gx16;
 		ast->mclk = 396;
-	}
-	else
-	{
+		return 0;
+	case ast_use_dt:
+		/*
+		 * If some properties are missing, use reasonable
+		 * defaults for AST2400
+		 */
+		if (of_property_read_u32(np, "ast,mcr-configuration", &mcr_cfg))
+			mcr_cfg = 0x00000577;
+		if (of_property_read_u32(np, "ast,ast,mcr-scu-mpll",
+					 &mcr_scu_mpll))
+			mcr_scu_mpll = 0x000050C0;
+		if (of_property_read_u32(np, "ast,ast,mcr-scu-strap",
+					 &mcr_scu_strap))
+			mcr_scu_strap = 0;
+		break;
+	case ast_use_p2a:
 		ast_write32(ast, 0xf004, 0x1e6e0000);
 		ast_write32(ast, 0xf000, 0x1);
-		data = ast_read32(ast, 0x10004);
-
-		if (data & 0x40)
-			ast->dram_bus_width = 16;
-		else
-			ast->dram_bus_width = 32;
+		mcr_cfg = ast_read32(ast, 0x10004);
+		mcr_scu_mpll = ast_read32(ast, 0x10120);
+		mcr_scu_strap = ast_read32(ast, 0x10170);
+		break;
+	}
 
-		if (ast->chip == AST2300 || ast->chip == AST2400) {
-			switch (data & 0x03) {
-			case 0:
-				ast->dram_type = AST_DRAM_512Mx16;
-				break;
-			default:
-			case 1:
-				ast->dram_type = AST_DRAM_1Gx16;
-				break;
-			case 2:
-				ast->dram_type = AST_DRAM_2Gx16;
-				break;
-			case 3:
-				ast->dram_type = AST_DRAM_4Gx16;
-				break;
-			}
-		} else {
-			switch (data & 0x0c) {
-			case 0:
-			case 4:
-				ast->dram_type = AST_DRAM_512Mx16;
-				break;
-			case 8:
-				if (data & 0x40)
-					ast->dram_type = AST_DRAM_1Gx16;
-				else
-					ast->dram_type = AST_DRAM_512Mx32;
-				break;
-			case 0xc:
-				ast->dram_type = AST_DRAM_1Gx32;
-				break;
-			}
-		}
+	if (mcr_cfg & 0x40)
+		ast->dram_bus_width = 16;
+	else
+		ast->dram_bus_width = 32;
 
-		data = ast_read32(ast, 0x10120);
-		data2 = ast_read32(ast, 0x10170);
-		if (data2 & 0x2000)
-			ref_pll = 14318;
-		else
-			ref_pll = 12000;
-
-		denum = data & 0x1f;
-		num = (data & 0x3fe0) >> 5;
-		data = (data & 0xc000) >> 14;
-		switch (data) {
-		case 3:
-			div = 0x4;
+	if (ast->chip == AST2300 || ast->chip == AST2400) {
+		switch (mcr_cfg & 0x03) {
+		case 0:
+			ast->dram_type = AST_DRAM_512Mx16;
 			break;
-		case 2:
+		default:
 		case 1:
-			div = 0x2;
+			ast->dram_type = AST_DRAM_1Gx16;
 			break;
-		default:
-			div = 0x1;
+		case 2:
+			ast->dram_type = AST_DRAM_2Gx16;
+			break;
+		case 3:
+			ast->dram_type = AST_DRAM_4Gx16;
+			break;
+		}
+	} else {
+		switch (mcr_cfg & 0x0c) {
+		case 0:
+		case 4:
+			ast->dram_type = AST_DRAM_512Mx16;
+			break;
+		case 8:
+			if (mcr_cfg & 0x40)
+				ast->dram_type = AST_DRAM_1Gx16;
+			else
+				ast->dram_type = AST_DRAM_512Mx32;
+			break;
+		case 0xc:
+			ast->dram_type = AST_DRAM_1Gx32;
 			break;
 		}
-		ast->mclk = ref_pll * (num + 2) / (denum + 2) * (div * 1000);
 	}
+
+	if (mcr_scu_strap & 0x2000)
+		ref_pll = 14318;
+	else
+		ref_pll = 12000;
+
+	denum = mcr_scu_mpll & 0x1f;
+	num = (mcr_scu_mpll & 0x3fe0) >> 5;
+	dsel = (mcr_scu_mpll & 0xc000) >> 14;
+	switch (dsel) {
+	case 3:
+		div = 0x4;
+		break;
+	case 2:
+	case 1:
+		div = 0x2;
+		break;
+	default:
+		div = 0x1;
+		break;
+	}
+	ast->mclk = ref_pll * (num + 2) / (denum + 2) * (div * 1000);
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/ast/ast_post.c b/drivers/gpu/drm/ast/ast_post.c
index 5331ee1..7197635 100644
--- a/drivers/gpu/drm/ast/ast_post.c
+++ b/drivers/gpu/drm/ast/ast_post.c
@@ -379,17 +379,14 @@  void ast_post_gpu(struct drm_device *dev)
 	ast_open_key(ast);
 	ast_set_def_ext_reg(dev);
 
-	if (ast->DisableP2A == false)
-	{
+	if (ast->config_mode == ast_use_p2a) {
 		if (ast->chip == AST2300 || ast->chip == AST2400)
 			ast_init_dram_2300(dev);
 		else
 			ast_init_dram_reg(dev);
 
 		ast_init_3rdtx(dev);
-	}
-	else
-	{
+	} else {
 		if (ast->tx_chip_type != AST_TX_NONE)
 			ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xa3, 0xcf, 0x80);	/* Enable DVO */
 	}