[PATCH v2 1/1] mfd: intel-lpss: Try to enable Memory-Write-Invalidate

[PATCH v2 1/1] mfd: intel-lpss: Try to enable Memory-Write-Invalidate

[Andy Shevchenko]

Enable MWI mechanism if PCI bus master supports it.

It might be potential benefit in some cases. Documentation [1] says that
standard Memory Write might supply more current data than in the CPU modified
cache line and "trashing a line in the cache may trash some data that is more
current that in the memory line". This allows to avoid potential retries and
other performance degradation issues on the bus.

[1] PCI System Architecture, 4th edition, ISBN: 0-201-30974-2, pp.117-119.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
In v2:
- extend commit message
 drivers/mfd/intel-lpss-pci.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mfd/intel-lpss-pci.c b/drivers/mfd/intel-lpss-pci.c
index 50e78db..4756153 100644
--- a/drivers/mfd/intel-lpss-pci.c
+++ b/drivers/mfd/intel-lpss-pci.c
@@ -41,6 +41,7 @@ static int intel_lpss_pci_probe(struct pci_dev *pdev,
 
 	/* Probably it is enough to set this for iDMA capable devices only */
 	pci_set_master(pdev);
+	pci_try_set_mwi(pdev);
 
 	ret = intel_lpss_probe(&pdev->dev, info);
 	if (ret)
-- 
2.9.3

Re: [PATCH v2 1/1] mfd: intel-lpss: Try to enable Memory-Write-Invalidate

[Mika Westerberg]

On Tue, Nov 15, 2016 at 12:37:04PM +0200, Andy Shevchenko wrote:
> Enable MWI mechanism if PCI bus master supports it.
> 
> It might be potential benefit in some cases. Documentation [1] says that
> standard Memory Write might supply more current data than in the CPU modified
> cache line and "trashing a line in the cache may trash some data that is more
> current that in the memory line". This allows to avoid potential retries and
> other performance degradation issues on the bus.
> 
> [1] PCI System Architecture, 4th edition, ISBN: 0-201-30974-2, pp.117-119.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Re: [PATCH v2 1/1] mfd: intel-lpss: Try to enable Memory-Write-Invalidate

[Lee Jones]

On Tue, 15 Nov 2016, Andy Shevchenko wrote:

> Enable MWI mechanism if PCI bus master supports it.
> 
> It might be potential benefit in some cases. Documentation [1] says that
> standard Memory Write might supply more current data than in the CPU modified
> cache line and "trashing a line in the cache may trash some data that is more
> current that in the memory line". This allows to avoid potential retries and
> other performance degradation issues on the bus.
> 
> [1] PCI System Architecture, 4th edition, ISBN: 0-201-30974-2, pp.117-119.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> In v2:
> - extend commit message
>  drivers/mfd/intel-lpss-pci.c | 1 +
>  1 file changed, 1 insertion(+)

Applied, thanks.

> diff --git a/drivers/mfd/intel-lpss-pci.c b/drivers/mfd/intel-lpss-pci.c
> index 50e78db..4756153 100644
> --- a/drivers/mfd/intel-lpss-pci.c
> +++ b/drivers/mfd/intel-lpss-pci.c
> @@ -41,6 +41,7 @@ static int intel_lpss_pci_probe(struct pci_dev *pdev,
>  
>  	/* Probably it is enough to set this for iDMA capable devices only */
>  	pci_set_master(pdev);
> +	pci_try_set_mwi(pdev);
>  
>  	ret = intel_lpss_probe(&pdev->dev, info);
>  	if (ret)

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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