[PATCH] PCI/VGA: Make the vga_is_firmware_default() arch-independent

From: Sui Jingfeng <suijingfeng@loongson.cn>
To: suijingfeng@loongson.cn
Cc: bhelgaas@google.com, linux-pci@vger.kernel.org,
	loongson-kernel@lists.loongnix.cn, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org
Subject: [PATCH] PCI/VGA: Make the vga_is_firmware_default() arch-independent
Date: Thu,  3 Aug 2023 16:17:58 +0800	[thread overview]
Message-ID: <20230803081758.968742-1-suijingfeng@loongson.cn> (raw)
In-Reply-To: <20230801183706.702567-1-suijingfeng@loongson.cn>

Currently, the vga_is_firmware_default() function works on x86 and IA64
architectures, but it is a no-op on ARM64, PPC, RISC-V, etc. This patch
completes the implementation by tracking the firmware framebuffer's address
range. The added code is trying to identify the VRAM aperture that contains
the firmware framebuffer. Once found, related information about the VRAM
aperture will be tracked.

Note that the initial VRAM aperture (the one that contains firmware fb)
identification should be done before the PCI resource relocation. This is
because we need to lock the VRAM aperture before it is moved. We achieve
this by using DECLARE_PCI_FIXUP_CLASS_HEADER(), which ensures that
vga_arb_firmware_fb_addr_tracker() gets called before PCI resource
allocation.

This patch overcame the VRAM bar relocation issue by updating the cached
firmware framebuffer's address range accordingly if the VRAM bar of the
primary GPU do moved. We achieve that by monitoring the address changes of
the VRAM aperture.

This patch make the vga_is_firmware_default() function works on whatever
arch that has UEFI GOP support, including x86 and IA64. But at the first
step, we make it available only on platforms which PCI resource relocation
do happens. Once provided to be effective and reliable, it can be expanded
to other arch easily.

This patch is tested on LS3A5000+LS7A2000 platform and LS3A5000+LS7A1000
platform. This patch can be applied on pci-next (6.5.0-rc1+) branch cleanly

v2:
	* Fix test robot warnnings and fix typos

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/pci/vgaarb.c | 140 ++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 125 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
index 5a696078b382..1f2d464e5812 100644
--- a/drivers/pci/vgaarb.c
+++ b/drivers/pci/vgaarb.c
@@ -61,6 +61,82 @@ static bool vga_arbiter_used;
 static DEFINE_SPINLOCK(vga_lock);
 static DECLARE_WAIT_QUEUE_HEAD(vga_wait_queue);
 
+static struct firmware_fb_tracker {
+	/* The PCI(e) device who owns the firmware framebuffer */
+	struct pci_dev *pdev;
+	/* The index of the VRAM Bar */
+	unsigned int bar;
+	/* Firmware fb's offset from the VRAM aperture start */
+	resource_size_t offset;
+	/* The firmware fb's size, in bytes */
+	resource_size_t size;
+
+	/* Firmware fb's address range, suffer from change */
+	resource_size_t start;
+	resource_size_t end;
+} firmware_fb;
+
+static bool vga_arb_get_fb_range_from_screen_info(resource_size_t *start,
+						  resource_size_t *end)
+{
+	resource_size_t fb_start;
+	resource_size_t fb_end;
+	resource_size_t fb_size;
+
+	fb_start = screen_info.lfb_base;
+	if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
+		fb_start |= (u64)screen_info.ext_lfb_base << 32;
+
+	fb_size = screen_info.lfb_size;
+
+	/* No firmware framebuffer support */
+	if (!fb_start || !fb_size)
+		return false;
+
+	fb_end = fb_start + fb_size - 1;
+
+	*start = fb_start;
+	*end = fb_end;
+
+	return true;
+}
+
+static bool vga_arb_get_fb_range_from_tracker(resource_size_t *start,
+					      resource_size_t *end)
+{
+	struct pci_dev *pdev = firmware_fb.pdev;
+	resource_size_t new_vram_base;
+	resource_size_t new_fb_start;
+	resource_size_t old_fb_start;
+	resource_size_t old_fb_end;
+
+	/*
+	 * No firmware framebuffer support or no aperture that contains the
+	 * firmware FB is found. In this case, the firmware_fb.pdev will be
+	 * NULL. We will return immediately.
+	 */
+	if (!pdev)
+		return false;
+
+	new_vram_base = pdev->resource[firmware_fb.bar].start;
+	new_fb_start = new_vram_base + firmware_fb.offset;
+	old_fb_start = firmware_fb.start;
+	old_fb_end = firmware_fb.end;
+
+	if (new_fb_start != old_fb_start) {
+		firmware_fb.start = new_fb_start;
+		firmware_fb.end = new_fb_start + firmware_fb.size - 1;
+		vgaarb_dbg(&pdev->dev,
+			   "[0x%llx, 0x%llx] -> [0x%llx, 0x%llx]\n",
+			   (u64)old_fb_start, (u64)old_fb_end,
+			   (u64)firmware_fb.start, (u64)firmware_fb.end);
+	}
+
+	*start = firmware_fb.start;
+	*end = firmware_fb.end;
+
+	return true;
+}
 
 static const char *vga_iostate_to_str(unsigned int iostate)
 {
@@ -543,20 +619,21 @@ void vga_put(struct pci_dev *pdev, unsigned int rsrc)
 }
 EXPORT_SYMBOL(vga_put);
 
+/* Select the device owning the boot framebuffer if there is one */
 static bool vga_is_firmware_default(struct pci_dev *pdev)
 {
-#if defined(CONFIG_X86) || defined(CONFIG_IA64)
-	u64 base = screen_info.lfb_base;
-	u64 size = screen_info.lfb_size;
 	struct resource *r;
-	u64 limit;
-
-	/* Select the device owning the boot framebuffer if there is one */
+	resource_size_t fb_start;
+	resource_size_t fb_end;
+	bool ret;
 
-	if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
-		base |= (u64)screen_info.ext_lfb_base << 32;
-
-	limit = base + size;
+#if defined(CONFIG_X86) || defined(CONFIG_IA64)
+	ret = vga_arb_get_fb_range_from_screen_info(&fb_start, &fb_end);
+#else
+	ret = vga_arb_get_fb_range_from_tracker(&fb_start, &fb_end);
+#endif
+	if (!ret)
+		return false;
 
 	/* Does firmware framebuffer belong to us? */
 	pci_dev_for_each_resource(pdev, r) {
@@ -566,12 +643,10 @@ static bool vga_is_firmware_default(struct pci_dev *pdev)
 		if (!r->start || !r->end)
 			continue;
 
-		if (base < r->start || limit >= r->end)
-			continue;
-
-		return true;
+		if (fb_start >= r->start && fb_end <= r->end)
+			return true;
 	}
-#endif
+
 	return false;
 }
 
@@ -1555,3 +1630,38 @@ static int __init vga_arb_device_init(void)
 	return rc;
 }
 subsys_initcall_sync(vga_arb_device_init);
+
+static void vga_arb_firmware_fb_addr_tracker(struct pci_dev *pdev)
+{
+	resource_size_t fb_start;
+	resource_size_t fb_end;
+	unsigned int i;
+
+	if (!vga_arb_get_fb_range_from_screen_info(&fb_start, &fb_end))
+		return;
+
+	for (i = 0; i < PCI_STD_NUM_BARS; i++) {
+		struct resource *ap = &pdev->resource[i];
+
+		if (resource_type(ap) != IORESOURCE_MEM)
+			continue;
+
+		if (!ap->start || !ap->end)
+			continue;
+
+		if (ap->start <= fb_start && fb_end <= ap->end) {
+			firmware_fb.pdev = pdev;
+			firmware_fb.bar = i;
+			firmware_fb.size = fb_end - fb_start + 1;
+			firmware_fb.offset = fb_start - ap->start;
+			firmware_fb.start = fb_start;
+			firmware_fb.end = fb_end;
+
+			vgaarb_dbg(&pdev->dev,
+				   "BAR %u contains firmware FB\n", i);
+			break;
+		}
+	}
+}
+DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_CLASS_DISPLAY_VGA,
+			       8, vga_arb_firmware_fb_addr_tracker);
-- 
2.34.1

