Subject: Re: [PATCH 1/1] powerpc: Force 32 bit MSIs on systems lacking firmware support

From: Mike Qiu <[email-masked]>
Date: Wed, 22 May 2013 14:28:24 +0800

于 2013/5/22 5:54, Brian King 写道:
> Recent commit e61133dda480062d221f09e4fc18f66763f8ecd0 added support
> for a new firmware feature to force an adapter to use 32 bit MSIs.
> However, this firmware is not available for all systems. The hack below
> allows devices needing 32 bit MSIs to work on these systems as well.
> It is careful to only enable this on Gen2 slots, which should limit
> this to configurations where this hack is needed and tested to work.
>
> Signed-off-by: Brian King <[email-masked]>
> ---
>
>   arch/powerpc/platforms/pseries/msi.c |   31 +++++++++++++++++++++++++++----
>   1 file changed, 27 insertions(+), 4 deletions(-)
>
> diff -puN arch/powerpc/platforms/pseries/msi.c~powerpc_32bit_msi_hack_on_papr arch/powerpc/platforms/pseries/msi.c
> --- linux/arch/powerpc/platforms/pseries/msi.c~powerpc_32bit_msi_hack_on_papr	2013-05-15 10:44:46.000000000 -0500
> +++ linux-bjking1/arch/powerpc/platforms/pseries/msi.c	2013-05-20 15:24:52.000000000 -0500
> @@ -397,10 +397,11 @@ static int check_msix_entries(struct pci
>   static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec_in, int type)
>   {
>   	struct pci_dn *pdn;
> -	int hwirq, virq, i, rc;
> +	int hwirq, virq, i, rc = -1;
>   	struct msi_desc *entry;
>   	struct msi_msg msg;
>   	int nvec = nvec_in;
> +	int use_32bit_msi_hack = 0;
>
>   	pdn = get_pdn(pdev);
>   	if (!pdn)
> @@ -428,15 +429,37 @@ static int rtas_setup_msi_irqs(struct pc
>   	 */
>   again:
>   	if (type == PCI_CAP_ID_MSI) {
> -		if (pdn->force_32bit_msi)
> +		if (pdn->force_32bit_msi) {
>   			rc = rtas_change_msi(pdn, RTAS_CHANGE_32MSI_FN, nvec);
> -		else
> +			if (rc < 0) {
> +				/* We only want to run the 32 bit MSI hack below if
> +				 the max bus speed is Gen2 speed. */
> +				if (pdev->bus->max_bus_speed != PCIE_SPEED_5_0GT)
> +					return rc;
> +
> +				use_32bit_msi_hack = 1;
> +			}
> +		}
> +
> +		if (rc < 0)
>   			rc = rtas_change_msi(pdn, RTAS_CHANGE_MSI_FN, nvec);
>
> -		if (rc < 0 && !pdn->force_32bit_msi) {
> +		if (rc < 0) {
>   			pr_debug("rtas_msi: trying the old firmware call.\n");
>   			rc = rtas_change_msi(pdn, RTAS_CHANGE_FN, nvec);
>   		}
> +
> +		if (use_32bit_msi_hack && rc > 0) {
> +			int pos;
> +			u32 addr_hi, addr_lo;
> +
> +			dev_info(&pdev->dev, "rtas_msi: No 32 bit MSI firmware support, forcing 32 bit MSI\n");
> +			pos = pci_find_capability(pdev, PCI_CAP_ID_MSI);
> +			pci_read_config_dword(pdev, pos + PCI_MSI_ADDRESS_HI, &addr_hi);
> +			addr_lo = 0xffff0000 | ((addr_hi >> (48 - 32)) << 4);
> +			pci_write_config_dword(pdev, pos + PCI_MSI_ADDRESS_LO, addr_lo);
> +			pci_write_config_dword(pdev, pos + PCI_MSI_ADDRESS_HI, 0);
I think here you can use catched dev->msi_cap for better.

Thanks
Mike
> +		}
>   	} else
>   		rc = rtas_change_msi(pdn, RTAS_CHANGE_MSIX_FN, nvec);
>
> _
>
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