linux-kernel - Re: [PATCH 3/3] arch/tile: tilegx PCI root complex support

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Date:	Mon, 9 Apr 2012 13:59:12 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Chris Metcalf <cmetcalf@...era.com>
Cc:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Myron Stowe <myron.stowe@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>, Joe Perches <joe@...ches.com>,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH 3/3] arch/tile: tilegx PCI root complex support

On Saturday 07 April 2012, Chris Metcalf wrote:
> This change implements PCIe root complex support for tilegx using
> the kernel support layer for accessing the TRIO hardware shim.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>

Hi Chris,

I don't know if we discussed it during the initial merge, but I notice that the PIO
accessors (inb/outb and friends) are still not implemented in this patch. Normally
PIO can just be mapped into the MMIO address space, so that inb() becomes
a call to readb() with an offset on the address.

> +/*
> + * Second PCI initialization entry point, called by subsys_initcall.
> + *
> + * The controllers have been set up by the time we get here, by a call to
> + * tile_pci_init.
> + */
> +int __devinit pcibios_init(void)
> +{
> +	resource_size_t offset;
> +	int i;
> +
> +        if (num_rc_controllers == 0 && num_ep_controllers == 0)
> +		return 0;
> +
> +	pr_info("PCI: Probing PCI hardware\n");
> +
> +	/*
> +	 * We loop over all the TRIO shims and set up the MMIO mappings.
> +	 * This step can't be done in tile_pci_init because the MM subsystem
> +	 * hasn't been initialized then.
> +	 */
> +	for (i = 0; i < TILEGX_NUM_TRIO; i++) {
> +		gxio_trio_context_t *context = &trio_contexts[i];
> +
> +		if (context->fd < 0)
> +			continue;
> +
> +		/*
> +		 * Map in the MMIO space for the MAC.
> +                 */
> +		offset = 0;
> +		context->mmio_base_mac =
> +			iorpc_ioremap(context->fd, offset,
> +				      HV_TRIO_CONFIG_IOREMAP_SIZE);
> +		if (context->mmio_base_mac == NULL) {
> +			pr_err("PCI: MAC map failure on TRIO %d\n", i);
> +
> +			hv_dev_close(context->fd);
> +			context->fd = -1;
> +			continue;
> +		}
> +	}
> +
> +	/*
> +	 * Delay a bit in case devices aren't ready.  Some devices are
> +	 * known to require at least 20ms here, but we use a more
> +	 * conservative value.
> +	 */
> +	mdelay(250);

Using mdelay is generally considered very rude. Since you are not in atomic
context here, just use msleep() instead.

	Arnd
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