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SubjectRe: [PATCH] fix Intel RNG detection
Date
On Thursday 27 July 2006 13:23, Jan Beulich wrote:

> +#ifdef CONFIG_SMP
> +static volatile char __initdata waitflag;

I don't think we want to add yet another use of volatile
(see the kernel archives for why).
Use memory barriers instead, please.

> +static void __init intel_init_wait (void *unused)
> +{
> + while (waitflag) {
> + cpu_relax();
rmb();
}
> +}
> +#endif
> +
> static int __init mod_init(void)
> {
> int err = -ENODEV;
> + unsigned i;
> + struct pci_dev *dev = NULL;
> void __iomem *mem;
> - u8 hw_status;
> -
> - if (!pci_dev_present(pci_tbl))
> + unsigned long flags;
> + u8 bios_cntl_off, fwh_dec_en1_off;
> + u8 bios_cntl_val = 0xff, fwh_dec_en1_val = 0xff;
> + u8 hw_status, mfg, dvc;
> +
> + for (i = 0; !dev && pci_tbl[i].vendor; ++i)
> + dev = pci_get_device(pci_tbl[i].vendor,
> pci_tbl[i].device, NULL);
> +
> + if (!dev)
> goto out; /* Device not found. */
>
> + /* Check for Intel 82802 */
> + if (dev->device < 0x2640) {
> + fwh_dec_en1_off = 0xe3;
> + bios_cntl_off = 0x4e;
> + }
> + else {
> + fwh_dec_en1_off = 0xd9; /* high byte of 16-bit register
> */
> + bios_cntl_off = 0xdc;
> + }
> +
> + pci_read_config_byte(dev, fwh_dec_en1_off, &fwh_dec_en1_val);
> + pci_read_config_byte(dev, bios_cntl_off, &bios_cntl_val);
> +
> + mem = ioremap_nocache(0xffff0000, 2);
> + if (mem == NULL) {
> + pci_dev_put(dev);
> + err = -EBUSY;
> + goto out;
> + }
> +
> +#ifdef CONFIG_SMP
> + waitflag = 1;
wmb();
> + if (smp_call_function(intel_init_wait, NULL, 1, 0) != 0) {
> + waitflag = 0;
> + pci_dev_put(dev);
> + printk(KERN_ERR PFX "cannot run on all processors\n");
> + err = -EAGAIN;
> + goto err_unmap;
> + }
> +#else
> +#define waitflag err

That's really confusing magic.

> +#endif
> + local_irq_save(flags);
> +
> + if (!(fwh_dec_en1_val & 0x80))
> + pci_write_config_byte(dev, fwh_dec_en1_off,
> fwh_dec_en1_val | 0x80);
> + if (!(bios_cntl_val & 0x03))
> + pci_write_config_byte(dev, bios_cntl_off, bios_cntl_val
> | 0x01);
> +
> + writeb(0xff, mem);
> + writeb(0x90, mem);
> + mfg = readb(mem + 0);
> + dvc = readb(mem + 1);
> + writeb(0xff, mem);

Do these magic registers have names? Possible to use #defines for it?

> + if (!(bios_cntl_val & 0x03))
> + pci_write_config_byte(dev, bios_cntl_off,
> bios_cntl_val);
> + if (!(fwh_dec_en1_val & 0x80))
> + pci_write_config_byte(dev, fwh_dec_en1_off,
> fwh_dec_en1_val);

Same for these magic bitmasks.

> + local_irq_restore(flags);
> + waitflag = 0;
smp_wmb();
> +
> + iounmap(mem);
> + pci_dev_put(dev);
> +
> + if (mfg != 0x89 || (dvc & ~0x01) != 0xac) {

magic values...

> + printk(KERN_ERR PFX "FWH not detected\n");
> + err = -ENODEV;
> + goto out;
> + }
> +
> err = -ENOMEM;
> mem = ioremap(INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
> if (!mem)
> goto out;
> intel_rng.priv = (unsigned long)mem;
>
> - /* Check for Intel 82802 */
> + /* Check for Random Number Generator */
> err = -ENODEV;
> hw_status = hwstatus_get(mem);
> if ((hw_status & INTEL_RNG_PRESENT) == 0)

--
Greetings Michael.
-
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