Re: [PATCH] PCI: MSI: Restore read_msi_msg_desc(); add get_cached_msi_msg_desc()

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Fri, 2010-07-23 at 14:56 +0100, Ben Hutchings wrote:
> commit 2ca1af9aa3285c6a5f103ed31ad09f7399fc65d7 "PCI: MSI: Remove
> unsafe and unnecessary hardware access" changed read_msi_msg_desc() to
> return the last MSI message written instead of reading it from the
> device, since it may be called while the device is in a reduced
> power state.

Looks reasonable... Jesse ?

Cheers,
Ben.

> However, the pSeries platform code really does need to read messages
> from the device, since they are initially written by firmware.
> Therefore:
> - Restore the previous behaviour of read_msi_msg_desc()
> - Add new functions get_cached_msi_msg{,_desc}() which return the
>   last MSI message written
> - Use the new functions where appropriate
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
> ---
> Compile-tested only.
> 
> Ben.
> 
>  arch/ia64/kernel/msi_ia64.c    |    2 +-
>  arch/ia64/sn/kernel/msi_sn.c   |    2 +-
>  arch/x86/kernel/apic/io_apic.c |    2 +-
>  drivers/pci/msi.c              |   47 +++++++++++++++++++++++++++++++++++----
>  include/linux/msi.h            |    2 +
>  5 files changed, 47 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/ia64/kernel/msi_ia64.c b/arch/ia64/kernel/msi_ia64.c
> index 6c89228..4a746ea 100644
> --- a/arch/ia64/kernel/msi_ia64.c
> +++ b/arch/ia64/kernel/msi_ia64.c
> @@ -25,7 +25,7 @@ static int ia64_set_msi_irq_affinity(unsigned int irq,
>  	if (irq_prepare_move(irq, cpu))
>  		return -1;
>  
> -	read_msi_msg(irq, &msg);
> +	get_cached_msi_msg(irq, &msg);
>  
>  	addr = msg.address_lo;
>  	addr &= MSI_ADDR_DEST_ID_MASK;
> diff --git a/arch/ia64/sn/kernel/msi_sn.c b/arch/ia64/sn/kernel/msi_sn.c
> index ebfdd6a..0c72dd4 100644
> --- a/arch/ia64/sn/kernel/msi_sn.c
> +++ b/arch/ia64/sn/kernel/msi_sn.c
> @@ -175,7 +175,7 @@ static int sn_set_msi_irq_affinity(unsigned int irq,
>  	 * Release XIO resources for the old MSI PCI address
>  	 */
>  
> -	read_msi_msg(irq, &msg);
> +	get_cached_msi_msg(irq, &msg);
>          sn_pdev = (struct pcidev_info *)sn_irq_info->irq_pciioinfo;
>  	pdev = sn_pdev->pdi_linux_pcidev;
>  	provider = SN_PCIDEV_BUSPROVIDER(pdev);
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index e41ed24..4dc0084 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -3397,7 +3397,7 @@ static int set_msi_irq_affinity(unsigned int irq, const struct cpumask *mask)
>  
>  	cfg = desc->chip_data;
>  
> -	read_msi_msg_desc(desc, &msg);
> +	get_cached_msi_msg_desc(desc, &msg);
>  
>  	msg.data &= ~MSI_DATA_VECTOR_MASK;
>  	msg.data |= MSI_DATA_VECTOR(cfg->vector);
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 4c14f31..69b7be3 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -197,9 +197,46 @@ void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
>  {
>  	struct msi_desc *entry = get_irq_desc_msi(desc);
>  
> -	/* We do not touch the hardware (which may not even be
> -	 * accessible at the moment) but return the last message
> -	 * written.  Assert that this is valid, assuming that
> +	BUG_ON(entry->dev->current_state != PCI_D0);
> +
> +	if (entry->msi_attrib.is_msix) {
> +		void __iomem *base = entry->mask_base +
> +			entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;
> +
> +		msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
> +		msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
> +		msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
> +	} else {
> +		struct pci_dev *dev = entry->dev;
> +		int pos = entry->msi_attrib.pos;
> +		u16 data;
> +
> +		pci_read_config_dword(dev, msi_lower_address_reg(pos),
> +					&msg->address_lo);
> +		if (entry->msi_attrib.is_64) {
> +			pci_read_config_dword(dev, msi_upper_address_reg(pos),
> +						&msg->address_hi);
> +			pci_read_config_word(dev, msi_data_reg(pos, 1), &data);
> +		} else {
> +			msg->address_hi = 0;
> +			pci_read_config_word(dev, msi_data_reg(pos, 0), &data);
> +		}
> +		msg->data = data;
> +	}
> +}
> +
> +void read_msi_msg(unsigned int irq, struct msi_msg *msg)
> +{
> +	struct irq_desc *desc = irq_to_desc(irq);
> +
> +	read_msi_msg_desc(desc, msg);
> +}
> +
> +void get_cached_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
> +{
> +	struct msi_desc *entry = get_irq_desc_msi(desc);
> +
> +	/* Assert that the cache is valid, assuming that
>  	 * valid messages are not all-zeroes. */
>  	BUG_ON(!(entry->msg.address_hi | entry->msg.address_lo |
>  		 entry->msg.data));
> @@ -207,11 +244,11 @@ void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
>  	*msg = entry->msg;
>  }
>  
> -void read_msi_msg(unsigned int irq, struct msi_msg *msg)
> +void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
>  {
>  	struct irq_desc *desc = irq_to_desc(irq);
>  
> -	read_msi_msg_desc(desc, msg);
> +	get_cached_msi_msg_desc(desc, msg);
>  }
>  
>  void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 6991ab5..91b05c1 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -14,8 +14,10 @@ struct irq_desc;
>  extern void mask_msi_irq(unsigned int irq);
>  extern void unmask_msi_irq(unsigned int irq);
>  extern void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg);
> +extern void get_cached_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg);
>  extern void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg);
>  extern void read_msi_msg(unsigned int irq, struct msi_msg *msg);
> +extern void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
>  extern void write_msi_msg(unsigned int irq, struct msi_msg *msg);
>  
>  struct msi_desc {
> -- 
> 1.6.2.5
>