diff mbox series

[2/4] PCI: Add pci_rebar_bytes_to_size()

Message ID 20210107175017.15893-3-nirmoy.das@amd.com (mailing list archive)
State New, archived
Headers show
Series A PCI quirk for resizable BAR 0 on Navi10 | expand

Commit Message

Das, Nirmoy Jan. 7, 2021, 5:50 p.m. UTC
Users of pci_resize_resource() need a way to calculate bar size
from desired bytes. Add a helper function and export it so that
modular drivers can use it.

Signed-off-by: Darren Salt <devspam@moreofthesa.me.uk>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
---
 drivers/pci/pci.c   | 2 +-
 include/linux/pci.h | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

Comments

Bjorn Helgaas Jan. 7, 2021, 9:17 p.m. UTC | #1
On Thu, Jan 07, 2021 at 06:50:15PM +0100, Nirmoy Das wrote:
> Users of pci_resize_resource() need a way to calculate bar size
> from desired bytes. Add a helper function and export it so that
> modular drivers can use it.

s/bar/BAR/

> Signed-off-by: Darren Salt <devspam@moreofthesa.me.uk>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
>  drivers/pci/pci.c   | 2 +-
>  include/linux/pci.h | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index ef80ed451415..16216186b51c 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1648,7 +1648,7 @@ static void pci_restore_rebar_state(struct pci_dev *pdev)
>  		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
>  		bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
>  		res = pdev->resource + bar_idx;
> -		size = ilog2(resource_size(res)) - 20;
> +		size = pci_rebar_bytes_to_size(resource_size(res));
>  		ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
>  		ctrl |= size << PCI_REBAR_CTRL_BAR_SHIFT;
>  		pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 9999040cfad9..77fed01523e0 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1226,6 +1226,12 @@ void pci_update_resource(struct pci_dev *dev, int resno);
>  int __must_check pci_assign_resource(struct pci_dev *dev, int i);
>  int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
>  void pci_release_resource(struct pci_dev *dev, int resno);
> +static inline int pci_rebar_bytes_to_size(u64 bytes)
> +{
> +	bytes = roundup_pow_of_two(bytes);
> +	return max(ilog2(bytes), 20) - 20;

This isn't returning a "size", is it?  It looks like it's returning
the log2 of the number of MB the BAR will be, i.e., the encoding used
by the Resizable BAR Control register "BAR Size" field.  Needs a brief
comment to that effect and/or a different function name.

> +}
> +
>  u32 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar);
>  int __must_check pci_resize_resource(struct pci_dev *dev, int i, int size);
>  int pci_select_bars(struct pci_dev *dev, unsigned long flags);
> -- 
> 2.29.2
>
Darren Salt Jan. 7, 2021, 11:31 p.m. UTC | #2
I demand that Bjorn Helgaas may or may not have written...

>> +static inline int pci_rebar_bytes_to_size(u64 bytes)
>> +{
>> +	bytes = roundup_pow_of_two(bytes);
>> +	return max(ilog2(bytes), 20) - 20;

> This isn't returning a "size", is it?  It looks like it's returning the
> log2 of the number of MB the BAR will be, i.e., the encoding used by the
> Resizable BAR Control register "BAR Size" field.  Needs a brief comment to
> that effect and/or a different function name.

Given that, it seems to me that pci_rebar_size_to_bytes should be similarly
commented and/or renamed.
Bjorn Helgaas Jan. 8, 2021, 1:01 a.m. UTC | #3
On Thu, Jan 07, 2021 at 11:31:36PM +0000, Darren Salt wrote:
> I demand that Bjorn Helgaas may or may not have written...

?

> >> +static inline int pci_rebar_bytes_to_size(u64 bytes)
> >> +{
> >> +	bytes = roundup_pow_of_two(bytes);
> >> +	return max(ilog2(bytes), 20) - 20;
> 
> > This isn't returning a "size", is it?  It looks like it's returning the
> > log2 of the number of MB the BAR will be, i.e., the encoding used by the
> > Resizable BAR Control register "BAR Size" field.  Needs a brief comment to
> > that effect and/or a different function name.
> 
> Given that, it seems to me that pci_rebar_size_to_bytes should be similarly
> commented and/or renamed.

Makes sense.  Something like this is sufficient:

  return 1ULL << (size + 20);  /* Convert PCI_REBAR_CTRL "BAR Size" */
diff mbox series

Patch

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index ef80ed451415..16216186b51c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1648,7 +1648,7 @@  static void pci_restore_rebar_state(struct pci_dev *pdev)
 		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
 		bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
 		res = pdev->resource + bar_idx;
-		size = ilog2(resource_size(res)) - 20;
+		size = pci_rebar_bytes_to_size(resource_size(res));
 		ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
 		ctrl |= size << PCI_REBAR_CTRL_BAR_SHIFT;
 		pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9999040cfad9..77fed01523e0 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1226,6 +1226,12 @@  void pci_update_resource(struct pci_dev *dev, int resno);
 int __must_check pci_assign_resource(struct pci_dev *dev, int i);
 int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
 void pci_release_resource(struct pci_dev *dev, int resno);
+static inline int pci_rebar_bytes_to_size(u64 bytes)
+{
+	bytes = roundup_pow_of_two(bytes);
+	return max(ilog2(bytes), 20) - 20;
+}
+
 u32 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar);
 int __must_check pci_resize_resource(struct pci_dev *dev, int i, int size);
 int pci_select_bars(struct pci_dev *dev, unsigned long flags);