[PATCH 1/9] drm/ast: Handle configuration without P2A bridge

* [PATCH 1/9] drm/ast: Handle configuration without P2A bridge
@ 2017-02-17  5:32 Benjamin Herrenschmidt
  2017-02-17  5:32 ` [PATCH 2/9] drm/ast: const'ify mode setting tables Benjamin Herrenschmidt
                   ` (9 more replies)
  0 siblings, 10 replies; 16+ messages in thread
From: Benjamin Herrenschmidt @ 2017-02-17  5:32 UTC (permalink / raw)
  To: dri-devel; +Cc: airlied, eich

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 went in to try to check if that window is open
but it does so by trying to access the registers in question
and testing if the result is 0xffffffff.

This method will trigger a PCIe error when the window is closed
which on some systems will be fatal (it will trigger an EEH
for example on POWER which will take out the device).

This patch improves this in two ways:

 - First, if the firmware has put properties in the device-tree
containing the relevant configuration information, we use these.

 - Otherwise, a bit in one of the SCU scratch registers (which
are readable via the VGA register space and writeable by the BMC)
will indicate if the BMC has closed the window. This bit has been
defined by Y.C Chen from Aspeed.

If the window is closed and the configuration isn't available from
the device-tree, some sane defaults are used. Those defaults are
hopefully sufficient for standard video modes used on a server.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
--

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

v3. [BenH]
    - Moved the config mode detection to a separate functionn
    - Add reading of SCU 0x40 D[12] to detect the window is
      closed as to not trigger a bus error by just "trying".
      (change provided by Y.C. Chen)
---
 drivers/gpu/drm/ast/ast_drv.h  |   6 +-
 drivers/gpu/drm/ast/ast_main.c | 223 +++++++++++++++++++++++++----------------
 drivers/gpu/drm/ast/ast_post.c |   7 +-
 3 files changed, 141 insertions(+), 95 deletions(-)

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..823c68f 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -62,13 +62,58 @@ uint8_t ast_get_index_reg_mask(struct ast_private *ast,
 	return ret;
 }
 
+static void ast_detect_config_mode(struct drm_device *dev, u32 *scu_rev)
+{
+	struct device_node *np = dev->pdev->dev.of_node;
+	struct ast_private *ast = dev->dev_private;
+	uint32_t data, jreg;
+
+	/* 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");
+		return;
+	}
+
+	/*
+	 * The BMC will set SCU 0x40 D[12] to 1 if the P2 bridge
+	 * is disabled
+	 */
+	jreg = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xd1, 0xff);
+	if (!(jreg & 0x10)) {
+		/* Double check it's actually working */
+		data = ast_read32(ast, 0xf004);
+		if (data != 0xFFFFFFFF) {
+			/* 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);
+			return;
+		}
+	}
+
+	DRM_INFO("P2A bridge disabled, using default configuration\n");
+	ast->config_mode = ast_use_defaults;
+	*scu_rev = 0xffffffff;
+}
 
 static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 {
 	struct ast_private *ast = dev->dev_private;
-	uint32_t data, jreg;
+	uint32_t jreg, scu_rev;
+
 	ast_open_key(ast);
 
+	/* Find out whether P2A works or whether to use device-tree */
+	ast_detect_config_mode(dev, &scu_rev);
+
+	/* Identify chipset */
 	if (dev->pdev->device == PCI_CHIP_AST1180) {
 		ast->chip = AST1100;
 		DRM_INFO("AST 1180 detected\n");
@@ -80,12 +125,7 @@ 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 +164,6 @@ 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 +180,12 @@ 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 +249,101 @@ 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_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);
+		mcr_cfg = ast_read32(ast, 0x10004);
+		mcr_scu_mpll = ast_read32(ast, 0x10120);
+		mcr_scu_strap = ast_read32(ast, 0x10170);
+		break;
+	case ast_use_defaults:
+	default:
 		ast->dram_bus_width = 16;
 		ast->dram_type = AST_DRAM_1Gx16;
 		ast->mclk = 396;
+		return 0;
 	}
-	else
-	{
-		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;
 
-		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;
 		}
-		ast->mclk = ref_pll * (num + 2) / (denum + 2) * (div * 1000);
+	} 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;
+		}
+	}
+
+	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 */
 	}
-- 
2.9.3

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