[PATCH 1/5] fbdev: tdfxfb: Add helper to read config table from BIOS

@@ -71,6 +71,7 @@
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
 #include <linux/fb.h>
 #include <linux/init.h>
 #include <linux/pci.h>

@@ -336,6 +337,79 @@ static u32 do_calc_pll(int freq, int *freq_out)
 	return (n << 8) | (m << 2) | k;
 }
 
+/*
+ * Convert a pllctrl register value back to a frequency in kHz.
+ * Formula from 3dfx documentation.
+ */
+static u32 tdfx_pll_to_khz(u32 pll)
+{
+	return (14318 * (((pll >> 8) & 0xff) + 2) /
+		(((pll >> 2) & 0x3f) + 2)) >> (pll & 3);
+}
+
+/* Layout of the "OEM config" table in voodoo 3 BIOS */
+struct tdfx_bios_cfg {
+	__le32 pciinit0;	/* 0x00 */
+	__le32 miscinit0;	/* 0x04 */
+	__le32 miscinit1;	/* 0x08 */
+	__le32 draminit0;	/* 0x0c */
+	__le32 draminit1;	/* 0x10 */
+	__le32 agpinit0;	/* 0x14 */
+	__le32 pllctrl1;	/* 0x18 - memory PLL */
+	__le32 pllctrl2;	/* 0x1c - graphics PLL */
+	__le32 sgrammode;	/* 0x20 - SGRAM/SDRAM mode register data */
+} __packed;
+
+#define TDFX_ROM_CFG_PTR	0x50
+
+static bool tdfxfb_get_bios_cfg(struct pci_dev *pdev,
+				struct tdfx_bios_cfg *cfg)
+{
+	u16 romcfg, oemcfg;
+	void __iomem *rom;
+	size_t romsize;
+	u8 *image;
+	u32 khz;
+
+	rom = pci_map_rom(pdev, &romsize);
+	if (!rom || !romsize)
+		return false;
+
+	image = vmalloc(romsize);
+	if (!image) {
+		pci_unmap_rom(pdev, rom);
+		return false;
+	}
+	memcpy_fromio(image, rom, romsize);
+	pci_unmap_rom(pdev, rom);
+
+	/* ROM[0x50] -> ROM config table -> OEM config table */
+	if (TDFX_ROM_CFG_PTR + 2 > romsize)
+		goto out;
+	romcfg = image[TDFX_ROM_CFG_PTR] | image[TDFX_ROM_CFG_PTR + 1] << 8;
+	if (romcfg == 0xffff || romcfg + 2 > romsize)
+		goto out;
+	oemcfg = image[romcfg] | image[romcfg + 1] << 8;
+	if (oemcfg == 0xffff || oemcfg + sizeof(*cfg) > romsize)
+		goto out;
+	memcpy(cfg, image + oemcfg, sizeof(*cfg));
+	vfree(image);
+
+	/*
+	 * Make sure we didn't read garbage from the BIOS and will
+	 * end up setting a frequency that explodes someone's expensive
+	 * card.
+	 */
+	khz = tdfx_pll_to_khz(le32_to_cpu(cfg->pllctrl1));
+	if (khz < 40000 || khz > 250000 || !le32_to_cpu(cfg->draminit0))
+		return false;
+	return true;
+
+out:
+	vfree(image);
+	return false;
+}
+
 static void do_write_regs(struct fb_info *info, struct banshee_reg *reg)
 {
 	struct tdfx_par *par = info->par;