Add support for routing PCIe DMA traffic coherently when
Cache Coherent Interconnect (CCI) is enabled in the system.
The "dma-coherent" property is used to determine if CCI is enabled
or not.
Refer to https://developer.arm.com/documentation/ddi0470/k/preface
for the CCI specification.
Signed-off-by: Bharat Kumar Gogada <[email protected]>
---
drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c b/drivers/pci/controller/pcie-xilinx-nwl.c
index 07e36661bbc2..8689311c5ef6 100644
--- a/drivers/pci/controller/pcie-xilinx-nwl.c
+++ b/drivers/pci/controller/pcie-xilinx-nwl.c
@@ -26,6 +26,7 @@
/* Bridge core config registers */
#define BRCFG_PCIE_RX0 0x00000000
+#define BRCFG_PCIE_RX1 0x00000004
#define BRCFG_INTERRUPT 0x00000010
#define BRCFG_PCIE_RX_MSG_FILTER 0x00000020
@@ -128,6 +129,7 @@
#define NWL_ECAM_VALUE_DEFAULT 12
#define CFG_DMA_REG_BAR GENMASK(2, 0)
+#define CFG_PCIE_CACHE GENMASK(7, 0)
#define INT_PCI_MSI_NR (2 * 32)
@@ -675,6 +677,11 @@ static int nwl_pcie_bridge_init(struct nwl_pcie *pcie)
nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
BRCFG_PCIE_RX_MSG_FILTER);
+ /* This routes the PCIe DMA traffic to go through CCI path */
+ if (of_dma_is_coherent(dev->of_node))
+ nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, BRCFG_PCIE_RX1) |
+ CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
+
err = nwl_wait_for_link(pcie);
if (err)
return err;
--
2.17.1
Add optional dma-coherent property to support coherent PCIe DMA traffic.
Signed-off-by: Bharat Kumar Gogada <[email protected]>
---
Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt | 2 ++
1 file changed, 2 insertions(+)
diff --git a/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt b/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
index 01bf7fdf4c19..2d677e90a7e2 100644
--- a/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
+++ b/Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt
@@ -33,6 +33,8 @@ Required properties:
- #address-cells: specifies the number of cells needed to encode an
address. The value must be 0.
+Optional properties:
+- dma-coherent: present if DMA operations are coherent
Example:
++++++++
--
2.17.1
Ping.
> -----Original Message-----
> From: Bharat Kumar Gogada <[email protected]>
> Sent: Monday, February 22, 2021 2:18 PM
> To: [email protected]; [email protected]
> Cc: [email protected]; Bharat Kumar Gogada <[email protected]>
> Subject: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic
> using CCI
>
> Add support for routing PCIe DMA traffic coherently when Cache Coherent
> Interconnect (CCI) is enabled in the system.
> The "dma-coherent" property is used to determine if CCI is enabled or not.
> Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> for the CCI specification.
>
> Signed-off-by: Bharat Kumar Gogada <[email protected]>
> ---
> drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c
> b/drivers/pci/controller/pcie-xilinx-nwl.c
> index 07e36661bbc2..8689311c5ef6 100644
> --- a/drivers/pci/controller/pcie-xilinx-nwl.c
> +++ b/drivers/pci/controller/pcie-xilinx-nwl.c
> @@ -26,6 +26,7 @@
>
> /* Bridge core config registers */
> #define BRCFG_PCIE_RX0 0x00000000
> +#define BRCFG_PCIE_RX1 0x00000004
> #define BRCFG_INTERRUPT 0x00000010
> #define BRCFG_PCIE_RX_MSG_FILTER 0x00000020
>
> @@ -128,6 +129,7 @@
> #define NWL_ECAM_VALUE_DEFAULT 12
>
> #define CFG_DMA_REG_BAR GENMASK(2, 0)
> +#define CFG_PCIE_CACHE GENMASK(7, 0)
>
> #define INT_PCI_MSI_NR (2 * 32)
>
> @@ -675,6 +677,11 @@ static int nwl_pcie_bridge_init(struct nwl_pcie
> *pcie)
> nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
> BRCFG_PCIE_RX_MSG_FILTER);
>
> + /* This routes the PCIe DMA traffic to go through CCI path */
> + if (of_dma_is_coherent(dev->of_node))
> + nwl_bridge_writel(pcie, nwl_bridge_readl(pcie,
> BRCFG_PCIE_RX1) |
> + CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> +
> err = nwl_wait_for_link(pcie);
> if (err)
> return err;
> --
> 2.17.1
Ping.
> -----Original Message-----
> From: Bharat Kumar Gogada
> Sent: Monday, March 15, 2021 11:43 AM
> To: Bharat Kumar Gogada <[email protected]>; linux-
> [email protected]; [email protected]
> Cc: [email protected]
> Subject: RE: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic
> using CCI
>
> Ping.
>
> > -----Original Message-----
> > From: Bharat Kumar Gogada <[email protected]>
> > Sent: Monday, February 22, 2021 2:18 PM
> > To: [email protected]; [email protected]
> > Cc: [email protected]; Bharat Kumar Gogada <[email protected]>
> > Subject: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA
> > traffic using CCI
> >
> > Add support for routing PCIe DMA traffic coherently when Cache
> > Coherent Interconnect (CCI) is enabled in the system.
> > The "dma-coherent" property is used to determine if CCI is enabled or not.
> > Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> > for the CCI specification.
> >
> > Signed-off-by: Bharat Kumar Gogada <[email protected]>
> > ---
> > drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c
> > b/drivers/pci/controller/pcie-xilinx-nwl.c
> > index 07e36661bbc2..8689311c5ef6 100644
> > --- a/drivers/pci/controller/pcie-xilinx-nwl.c
> > +++ b/drivers/pci/controller/pcie-xilinx-nwl.c
> > @@ -26,6 +26,7 @@
> >
> > /* Bridge core config registers */
> > #define BRCFG_PCIE_RX0 0x00000000
> > +#define BRCFG_PCIE_RX1 0x00000004
> > #define BRCFG_INTERRUPT 0x00000010
> > #define BRCFG_PCIE_RX_MSG_FILTER 0x00000020
> >
> > @@ -128,6 +129,7 @@
> > #define NWL_ECAM_VALUE_DEFAULT 12
> >
> > #define CFG_DMA_REG_BAR GENMASK(2, 0)
> > +#define CFG_PCIE_CACHE GENMASK(7, 0)
> >
> > #define INT_PCI_MSI_NR (2 * 32)
> >
> > @@ -675,6 +677,11 @@ static int nwl_pcie_bridge_init(struct nwl_pcie
> > *pcie)
> > nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
> > BRCFG_PCIE_RX_MSG_FILTER);
> >
> > + /* This routes the PCIe DMA traffic to go through CCI path */
> > + if (of_dma_is_coherent(dev->of_node))
> > + nwl_bridge_writel(pcie, nwl_bridge_readl(pcie,
> > BRCFG_PCIE_RX1) |
> > + CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> > +
> > err = nwl_wait_for_link(pcie);
> > if (err)
> > return err;
> > --
> > 2.17.1
Hi Lorenzo,
Any inputs on this ?
Regards,
Bharat
> -----Original Message-----
> From: Bharat Kumar Gogada
> Sent: Tuesday, March 23, 2021 4:48 PM
> To: Bharat Kumar Gogada <[email protected]>; linux-
> [email protected]; [email protected]
> Cc: [email protected]; Lorenzo Pieralisi <[email protected]>
> Subject: RE: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic
> using CCI
>
> Ping.
>
> > -----Original Message-----
> > From: Bharat Kumar Gogada
> > Sent: Monday, March 15, 2021 11:43 AM
> > To: Bharat Kumar Gogada <[email protected]>; linux-
> > [email protected]; [email protected]
> > Cc: [email protected]
> > Subject: RE: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA
> > traffic using CCI
> >
> > Ping.
> >
> > > -----Original Message-----
> > > From: Bharat Kumar Gogada <[email protected]>
> > > Sent: Monday, February 22, 2021 2:18 PM
> > > To: [email protected]; [email protected]
> > > Cc: [email protected]; Bharat Kumar Gogada <[email protected]>
> > > Subject: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA
> > > traffic using CCI
> > >
> > > Add support for routing PCIe DMA traffic coherently when Cache
> > > Coherent Interconnect (CCI) is enabled in the system.
> > > The "dma-coherent" property is used to determine if CCI is enabled or
> not.
> > > Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> > > for the CCI specification.
> > >
> > > Signed-off-by: Bharat Kumar Gogada <[email protected]>
> > > ---
> > > drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
> > > 1 file changed, 7 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c
> > > b/drivers/pci/controller/pcie-xilinx-nwl.c
> > > index 07e36661bbc2..8689311c5ef6 100644
> > > --- a/drivers/pci/controller/pcie-xilinx-nwl.c
> > > +++ b/drivers/pci/controller/pcie-xilinx-nwl.c
> > > @@ -26,6 +26,7 @@
> > >
> > > /* Bridge core config registers */
> > > #define BRCFG_PCIE_RX0 0x00000000
> > > +#define BRCFG_PCIE_RX1 0x00000004
> > > #define BRCFG_INTERRUPT 0x00000010
> > > #define BRCFG_PCIE_RX_MSG_FILTER 0x00000020
> > >
> > > @@ -128,6 +129,7 @@
> > > #define NWL_ECAM_VALUE_DEFAULT 12
> > >
> > > #define CFG_DMA_REG_BAR GENMASK(2, 0)
> > > +#define CFG_PCIE_CACHE GENMASK(7, 0)
> > >
> > > #define INT_PCI_MSI_NR (2 * 32)
> > >
> > > @@ -675,6 +677,11 @@ static int nwl_pcie_bridge_init(struct nwl_pcie
> > > *pcie)
> > > nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
> > > BRCFG_PCIE_RX_MSG_FILTER);
> > >
> > > + /* This routes the PCIe DMA traffic to go through CCI path */
> > > + if (of_dma_is_coherent(dev->of_node))
> > > + nwl_bridge_writel(pcie, nwl_bridge_readl(pcie,
> > > BRCFG_PCIE_RX1) |
> > > + CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> > > +
> > > err = nwl_wait_for_link(pcie);
> > > if (err)
> > > return err;
> > > --
> > > 2.17.1
[+ Rob, Robin]
On Mon, Feb 22, 2021 at 02:17:31PM +0530, Bharat Kumar Gogada wrote:
> Add support for routing PCIe DMA traffic coherently when
> Cache Coherent Interconnect (CCI) is enabled in the system.
> The "dma-coherent" property is used to determine if CCI is enabled
> or not.
> Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> for the CCI specification.
>
> Signed-off-by: Bharat Kumar Gogada <[email protected]>
> ---
> drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c b/drivers/pci/controller/pcie-xilinx-nwl.c
> index 07e36661bbc2..8689311c5ef6 100644
> --- a/drivers/pci/controller/pcie-xilinx-nwl.c
> +++ b/drivers/pci/controller/pcie-xilinx-nwl.c
> @@ -26,6 +26,7 @@
>
> /* Bridge core config registers */
> #define BRCFG_PCIE_RX0 0x00000000
> +#define BRCFG_PCIE_RX1 0x00000004
> #define BRCFG_INTERRUPT 0x00000010
> #define BRCFG_PCIE_RX_MSG_FILTER 0x00000020
>
> @@ -128,6 +129,7 @@
> #define NWL_ECAM_VALUE_DEFAULT 12
>
> #define CFG_DMA_REG_BAR GENMASK(2, 0)
> +#define CFG_PCIE_CACHE GENMASK(7, 0)
>
> #define INT_PCI_MSI_NR (2 * 32)
>
> @@ -675,6 +677,11 @@ static int nwl_pcie_bridge_init(struct nwl_pcie *pcie)
> nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
> BRCFG_PCIE_RX_MSG_FILTER);
>
> + /* This routes the PCIe DMA traffic to go through CCI path */
> + if (of_dma_is_coherent(dev->of_node))
> + nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, BRCFG_PCIE_RX1) |
> + CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> +
This is weird. FW is telling us that the RC is DMA coherent hence
we have to program the RC so that it is indeed DMA coherent.
It does not make much sense. I think this is a set-up that should be
programmed by firmware and reported to the kernel via the standard
"dma-coherent" property. The kernel can read that register to check the
HW configuration complies with the DT property.
I'd like to get RobH/Robin thoughts on this before proceeding - they
have more insights about the DT dma-coherent usage/bindings and
expected behaviour.
Thanks,
Lorenzo
> err = nwl_wait_for_link(pcie);
> if (err)
> return err;
> --
> 2.17.1
>
On Tue, Apr 6, 2021 at 9:20 AM Lorenzo Pieralisi
<[email protected]> wrote:
>
> [+ Rob, Robin]
>
> On Mon, Feb 22, 2021 at 02:17:31PM +0530, Bharat Kumar Gogada wrote:
> > Add support for routing PCIe DMA traffic coherently when
> > Cache Coherent Interconnect (CCI) is enabled in the system.
> > The "dma-coherent" property is used to determine if CCI is enabled
> > or not.
> > Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> > for the CCI specification.
> >
> > Signed-off-by: Bharat Kumar Gogada <[email protected]>
> > ---
> > drivers/pci/controller/pcie-xilinx-nwl.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c b/drivers/pci/controller/pcie-xilinx-nwl.c
> > index 07e36661bbc2..8689311c5ef6 100644
> > --- a/drivers/pci/controller/pcie-xilinx-nwl.c
> > +++ b/drivers/pci/controller/pcie-xilinx-nwl.c
> > @@ -26,6 +26,7 @@
> >
> > /* Bridge core config registers */
> > #define BRCFG_PCIE_RX0 0x00000000
> > +#define BRCFG_PCIE_RX1 0x00000004
> > #define BRCFG_INTERRUPT 0x00000010
> > #define BRCFG_PCIE_RX_MSG_FILTER 0x00000020
> >
> > @@ -128,6 +129,7 @@
> > #define NWL_ECAM_VALUE_DEFAULT 12
> >
> > #define CFG_DMA_REG_BAR GENMASK(2, 0)
> > +#define CFG_PCIE_CACHE GENMASK(7, 0)
> >
> > #define INT_PCI_MSI_NR (2 * 32)
> >
> > @@ -675,6 +677,11 @@ static int nwl_pcie_bridge_init(struct nwl_pcie *pcie)
> > nwl_bridge_writel(pcie, CFG_ENABLE_MSG_FILTER_MASK,
> > BRCFG_PCIE_RX_MSG_FILTER);
> >
> > + /* This routes the PCIe DMA traffic to go through CCI path */
> > + if (of_dma_is_coherent(dev->of_node))
> > + nwl_bridge_writel(pcie, nwl_bridge_readl(pcie, BRCFG_PCIE_RX1) |
> > + CFG_PCIE_CACHE, BRCFG_PCIE_RX1);
> > +
>
> This is weird. FW is telling us that the RC is DMA coherent hence
> we have to program the RC so that it is indeed DMA coherent.
>
> It does not make much sense. I think this is a set-up that should be
> programmed by firmware and reported to the kernel via the standard
> "dma-coherent" property. The kernel can read that register to check the
> HW configuration complies with the DT property.
>
> I'd like to get RobH/Robin thoughts on this before proceeding - they
> have more insights about the DT dma-coherent usage/bindings and
> expected behaviour.
Without the above change or firmware setup, a DT with 'dma-coherent'
and a kernel without it will be broken because the above register
won't be configured, yet we'll be using coherent DMA ops.
Originally when I added 'dma-coherent' (for Calxeda h/w), I had to do
all the coherent path setup in the kernel to ensure the h/w setup was
in-sync with the DMA ops. Nowadays, it's probably safe to assume the
OS has coherent support, but can we say that for sure for all OSs?
It also is going to depend if this register survives resets of the
module. If not, then it needs to be done in the kernel.
Rob
On Mon, 22 Feb 2021 14:17:31 +0530, Bharat Kumar Gogada wrote:
> Add support for routing PCIe DMA traffic coherently when
> Cache Coherent Interconnect (CCI) is enabled in the system.
> The "dma-coherent" property is used to determine if CCI is enabled
> or not.
> Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> for the CCI specification.
Applied to pci/xilinx, thanks!
[1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI
https://git.kernel.org/lpieralisi/pci/c/213e122052
[2/2] PCI: xilinx-nwl: Add optional "dma-coherent" property
https://git.kernel.org/lpieralisi/pci/c/1c4422f226
Thanks,
Lorenzo
Thanks Lorenzo.
> -----Original Message-----
> From: Lorenzo Pieralisi <[email protected]>
> Sent: Wednesday, April 7, 2021 9:32 PM
> To: [email protected]; Bharat Kumar Gogada <[email protected]>;
> [email protected]
> Cc: [email protected]; [email protected]
> Subject: Re: [PATCH v3 1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic
> using CCI
>
> On Mon, 22 Feb 2021 14:17:31 +0530, Bharat Kumar Gogada wrote:
> > Add support for routing PCIe DMA traffic coherently when Cache
> > Coherent Interconnect (CCI) is enabled in the system.
> > The "dma-coherent" property is used to determine if CCI is enabled or
> > not.
> > Refer to https://developer.arm.com/documentation/ddi0470/k/preface
> > for the CCI specification.
>
> Applied to pci/xilinx, thanks!
>
> [1/2] PCI: xilinx-nwl: Enable coherent PCIe DMA traffic using CCI
> https://git.kernel.org/lpieralisi/pci/c/213e122052
> [2/2] PCI: xilinx-nwl: Add optional "dma-coherent" property
> https://git.kernel.org/lpieralisi/pci/c/1c4422f226
>
> Thanks,
> Lorenzo