linux-kernel - Re: [ 65/79] powerpc/pseries: Make 32-bit MSI quirk work on systems lacking firmware support

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Date:	Wed, 12 Jun 2013 14:19:38 -0300
From:	Kleber Sacilotto de Souza <klebers@...ux.vnet.ibm.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Brian King <brking@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [ 65/79] powerpc/pseries: Make 32-bit MSI quirk work on systems
 lacking firmware support

On 06/11/2013 05:03 PM, Greg Kroah-Hartman wrote:
> 3.9-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Brian King <brking@...ux.vnet.ibm.com>
> 
> commit f1dd153121dcb872ae6cba8d52bec97519eb7d97 upstream.
> 
> 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.
> 
> [Small change to factor out the hack into a separate function -- BenH]
> 
> Signed-off-by: Brian King <brking@...ux.vnet.ibm.com>
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Signed-off-by: Kleber Sacilotto de Souza <klebers@...ux.vnet.ibm.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>   arch/powerpc/platforms/pseries/msi.c |   40 ++++++++++++++++++++++++++++++++---
>   1 file changed, 37 insertions(+), 3 deletions(-)
> 
> --- a/arch/powerpc/platforms/pseries/msi.c
> +++ b/arch/powerpc/platforms/pseries/msi.c
> @@ -394,6 +394,23 @@ static int check_msix_entries(struct pci
>   	return 0;
>   }
> 
> +static void rtas_hack_32bit_msi_gen2(struct pci_dev *pdev)
> +{
> +	u32 addr_hi, addr_lo;
> +
> +	/*
> +	 * We should only get in here for IODA1 configs. This is based on the
> +	 * fact that we using RTAS for MSIs, we don't have the 32 bit MSI RTAS
> +	 * support, and we are in a PCIe Gen2 slot.
> +	 */
> +	dev_info(&pdev->dev,
> +		 "rtas_msi: No 32 bit MSI firmware support, forcing 32 bit MSI\n");
> +	pci_read_config_dword(pdev, pdev->msi_cap + PCI_MSI_ADDRESS_HI, &addr_hi);
> +	addr_lo = 0xffff0000 | ((addr_hi >> (48 - 32)) << 4);
> +	pci_write_config_dword(pdev, pdev->msi_cap + PCI_MSI_ADDRESS_LO, addr_lo);
> +	pci_write_config_dword(pdev, pdev->msi_cap + PCI_MSI_ADDRESS_HI, 0);
> +}
> +
>   static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec_in, int type)
>   {
>   	struct pci_dn *pdn;
> @@ -401,6 +418,7 @@ static int rtas_setup_msi_irqs(struct pc
>   	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 +446,31 @@ 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;
> +			}
> +		} else
> +			rc = -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)
> +			rtas_hack_32bit_msi_gen2(pdev);
>   	} else
>   		rc = rtas_change_msi(pdn, RTAS_CHANGE_MSIX_FN, nvec);
> 
> 
> 

Greg,

This change depends on upstream commit e375b561817d9ae098cc4296a729fc88924a0159 to work, since this is when the msi_cap field was added to struct pci_dev. e375b561 was applied on 3.10-rc1 and it seems it is not on the stable tree, so in my request for the stable tree I sent a patch backported to 3.9.y with a modified version of rtas_hack_32bit_msi_gen2(). If e375b561 is not being brought to the stable tree as well, please consider the code I sent to the stable list on June/06, or else it will break the build for ppc.


Thank you,

-- 
Kleber Sacilotto de Souza
IBM Linux Technology Center

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