From: Li Chen <[email protected]>
Before this commit, epf cannot set BAR to be prefetchable.
Prefetchable BAR can also help epf device to use bridge's
prefetch memory window.
Signed-off-by: Li Chen <[email protected]>
---
Changes in v2:
Remove Gerrit Change-id
Changes in v3:
capitalize "BAR" in the subject and commit log as suggested by Bjorn.
Changes in v4:
This patch context doesn't change but resend with my Zoho mail account in that previous
company mail will contain un-removeable proprietary messages.
Add "From:" to the first line of the message body.
drivers/pci/endpoint/functions/pci-epf-test.c | 4 ++++
include/linux/pci-epc.h | 2 ++
2 files changed, 6 insertions(+)
diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 90d84d3bc868..96489cfdf58d 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -817,15 +817,19 @@ static void pci_epf_configure_bar(struct pci_epf *epf,
{
struct pci_epf_bar *epf_bar;
bool bar_fixed_64bit;
+ bool bar_prefetch;
int i;
for (i = 0; i < PCI_STD_NUM_BARS; i++) {
epf_bar = &epf->bar[i];
bar_fixed_64bit = !!(epc_features->bar_fixed_64bit & (1 << i));
+ bar_prefetch = !!(epc_features->bar_prefetch & (1 << i));
if (bar_fixed_64bit)
epf_bar->flags |= PCI_BASE_ADDRESS_MEM_TYPE_64;
if (epc_features->bar_fixed_size[i])
bar_size[i] = epc_features->bar_fixed_size[i];
+ if (bar_prefetch)
+ epf_bar->flags |= PCI_BASE_ADDRESS_MEM_PREFETCH;
}
}
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index a48778e1a4ee..825632d581d0 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -161,6 +161,7 @@ struct pci_epc {
* @msix_capable: indicate if the endpoint function has MSI-X capability
* @reserved_bar: bitmap to indicate reserved BAR unavailable to function driver
* @bar_fixed_64bit: bitmap to indicate fixed 64bit BARs
+ * @bar_prefetch: bitmap to indicate prefetchable BARs
* @bar_fixed_size: Array specifying the size supported by each BAR
* @align: alignment size required for BAR buffer allocation
*/
@@ -171,6 +172,7 @@ struct pci_epc_features {
unsigned int msix_capable : 1;
u8 reserved_bar;
u8 bar_fixed_64bit;
+ u8 bar_prefetch;
u64 bar_fixed_size[PCI_STD_NUM_BARS];
size_t align;
};
--
2.34.1
Reviewed-by: Shradha Todi <[email protected]>
This patch looks useful. Can we revisit this and get it merged?
>Date: Fri, 21 Jan 2022 12:12:56 +0800
>From: Li Chen <[email protected]>
>To: "Bjorn Helgaas" <[email protected]>
>Cc: "Kishon Vijay Abraham I" <[email protected]>,
> "Lorenzo Pieralisi" <[email protected]>,
> "Bjorn Helgaas" <[email protected]>,
> "linux-pci" <[email protected]>,
> "linux-kernel" <[email protected]>
>Message-ID: <[email protected]>
>In-Reply-To:
>Subject: [PATCH v4] PCI: endpoint: Add prefetch BAR support
>MIME-Version: 1.0
>Content-Type: text/plain; charset="UTF-8"
>Content-Transfer-Encoding: 7bit
>Importance: Medium
>User-Agent: Zoho Mail
>X-Mailer: Zoho Mail
>Precedence: bulk
>List-ID: <linux-pci.vger.kernel.org>
>X-Mailing-List: [email protected]
>
>From: Li Chen <[email protected]>
>
>Before this commit, epf cannot set BAR to be prefetchable.
>Prefetchable BAR can also help epf device to use bridge's
>prefetch memory window.
>
>Signed-off-by: Li Chen <[email protected]>
>---
>Changes in v2:
>Remove Gerrit Change-id
>Changes in v3:
>capitalize "BAR" in the subject and commit log as suggested by Bjorn.
>Changes in v4:
>This patch context doesn't change but resend with my Zoho mail account in that previous
>company mail will contain un-removeable proprietary messages.
>Add "From:" to the first line of the message body.
>
> drivers/pci/endpoint/functions/pci-epf-test.c | 4 ++++
> include/linux/pci-epc.h | 2 ++
> 2 files changed, 6 insertions(+)
>
>diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
>index 90d84d3bc868..96489cfdf58d 100644
>--- a/drivers/pci/endpoint/functions/pci-epf-test.c
>+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
>@@ -817,15 +817,19 @@ static void pci_epf_configure_bar(struct pci_epf *epf,
> {
> struct pci_epf_bar *epf_bar;
> bool bar_fixed_64bit;
>+ bool bar_prefetch;
> int i;
>
> for (i = 0; i < PCI_STD_NUM_BARS; i++) {
> epf_bar = &epf->bar[i];
> bar_fixed_64bit = !!(epc_features->bar_fixed_64bit & (1 << i));
>+ bar_prefetch = !!(epc_features->bar_prefetch & (1 << i));
> if (bar_fixed_64bit)
> epf_bar->flags |= PCI_BASE_ADDRESS_MEM_TYPE_64;
> if (epc_features->bar_fixed_size[i])
> bar_size[i] = epc_features->bar_fixed_size[i];
>+ if (bar_prefetch)
>+ epf_bar->flags |= PCI_BASE_ADDRESS_MEM_PREFETCH;
> }
> }
>
>diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
>index a48778e1a4ee..825632d581d0 100644
>--- a/include/linux/pci-epc.h
>+++ b/include/linux/pci-epc.h
>@@ -161,6 +161,7 @@ struct pci_epc {
> * @msix_capable: indicate if the endpoint function has MSI-X capability
> * @reserved_bar: bitmap to indicate reserved BAR unavailable to function driver
> * @bar_fixed_64bit: bitmap to indicate fixed 64bit BARs
>+ * @bar_prefetch: bitmap to indicate prefetchable BARs
> * @bar_fixed_size: Array specifying the size supported by each BAR
> * @align: alignment size required for BAR buffer allocation
> */
>@@ -171,6 +172,7 @@ struct pci_epc_features {
> unsigned int msix_capable : 1;
> u8 reserved_bar;
> u8 bar_fixed_64bit;
>+ u8 bar_prefetch;
> u64 bar_fixed_size[PCI_STD_NUM_BARS];
> size_t align;
> };
>--
>2.34.1
>
>
>
On Wed, Feb 28, 2024 at 07:14:48PM +0530, Shradha Todi wrote:
> Reviewed-by: Shradha Todi <[email protected]>
>
> This patch looks useful. Can we revisit this and get it merged?
Hello Shradha,
This patch is two years old, and no longer applies to pci-next.
However:
Usually, fixed hardware requirements are specified in
struct pci_epc_features (more specifically struct pci_epc_bar_desc).
A requested BAR configuration by an EPF is specified in struct epf_bar.
I don't think that Prefetch is a fixed hardware requirement,
so I do not think that we should put it in struct pci_epc_features.
It seems more like something that an endpoint function driver can
chose to request (or not to request), just like MEM_TYPE_64.
From the PCIe base spec:
"Generally only 64-bit BARs are good candidates, since only Legacy
Endpoints are permitted to set the Prefetchable bit in 32-bit BARs,
and most scalable platforms map all 32-bit Memory BARs into
non-prefetchable Memory Space regardless of the Prefetchable bit value."
"For a PCI Express Endpoint, 64-bit addressing must be supported for all BARs
that have the Prefetchable bit Set. 32-bit addressing is permitted for all BARs
that do not have the Prefetchable bit Set."
"Any device that has a range that behaves like normal memory should mark the
range as prefetchable. A linear frame buffer in a graphics device is an example
of a range that should be marked prefetchable."
We are not a legacy endpoint, so we should never set Prefetch for 32-bit BARs.
For 64-bit BARs, we should always set it, if the EPF-core allocated the memory
(regular memory) for that BAR.
Thus, I think the best solution is to do:
diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index cd4ffb39dcdc..186c8cd87bb3 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -879,7 +879,8 @@ static void pci_epf_configure_bar(struct pci_epf *epf,
for (i = 0; i < PCI_STD_NUM_BARS; i++) {
epf_bar = &epf->bar[i];
if (epc_features->bar[i].only_64bit)
- epf_bar->flags |= PCI_BASE_ADDRESS_MEM_TYPE_64;
+ epf_bar->flags |= (PCI_BASE_ADDRESS_MEM_TYPE_64 |
+ PCI_BASE_ADDRESS_MEM_PREFETCH);
}
}
diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index 0a28a0b0911b..acb93055181b 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -305,7 +305,8 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
epf_bar[bar].size = size;
epf_bar[bar].barno = bar;
epf_bar[bar].flags |= upper_32_bits(size) ?
- PCI_BASE_ADDRESS_MEM_TYPE_64 :
+ (PCI_BASE_ADDRESS_MEM_TYPE_64 |
+ PCI_BASE_ADDRESS_MEM_PREFETCH) :
PCI_BASE_ADDRESS_MEM_TYPE_32;
return space;
Now when I look at it, the whole "if (epc_features->bar[i].only_64bit)"
should move to pci_epf_alloc_space() IMO, so that not all EPF drivers need to
duplicate this code.
Kind regards,
Niklas