Re: [PATCH v4 6/9] PCI/PTM: Preserve RsvdP bits in PTM Control register

Sathyanarayanan Kuppuswamy
2022-09-09T23:46:55Z

On 9/9/22 1:25 PM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
>
> Even though only the low 16 bits of PTM Control are currently defined, the
> register is 32 bits wide and the unused bits are RsvdP ("Reserved and
> Preserved"), so software must preserve the values of those bits when
> writing the register.
>
> Update PTM Control reads and writes to use 32-bit accesses and preserve the
> reserved bits on writes.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

> drivers/pci/pcie/ptm.c | 25 ++++++++++++++-----------
> 1 file changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> index fc296b352fe2..5b8598b222b0 100644
> --- a/drivers/pci/pcie/ptm.c
> +++ b/drivers/pci/pcie/ptm.c
> @@ -12,14 +12,14 @@
> static void __pci_disable_ptm(struct pci_dev *dev)
> {
> u16 ptm = dev->ptm_cap;
> - u16 ctrl;
> + u32 ctrl;
>
> if (!ptm)
> return;
>
> - pci_read_config_word(dev, ptm + PCI_PTM_CTRL, &ctrl);
> + pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, &ctrl);
> ctrl &= ~(PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT);
> - pci_write_config_word(dev, ptm + PCI_PTM_CTRL, ctrl);
> + pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, ctrl);
> }
>
> /**
> @@ -41,7 +41,7 @@ void pci_save_ptm_state(struct pci_dev *dev)
> {
> u16 ptm = dev->ptm_cap;
> struct pci_cap_saved_state *save_state;
> - u16 *cap;
> + u32 *cap;
>
> if (!ptm)
> return;
> @@ -50,15 +50,15 @@ void pci_save_ptm_state(struct pci_dev *dev)
> if (!save_state)
> return;
>
> - cap = (u16 *)&save_state->cap.data[0];
> - pci_read_config_word(dev, ptm + PCI_PTM_CTRL, cap);
> + cap = (u32 *)&save_state->cap.data[0];
> + pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, cap);
> }
>
> void pci_restore_ptm_state(struct pci_dev *dev)
> {
> u16 ptm = dev->ptm_cap;
> struct pci_cap_saved_state *save_state;
> - u16 *cap;
> + u32 *cap;
>
> if (!ptm)
> return;
> @@ -67,8 +67,8 @@ void pci_restore_ptm_state(struct pci_dev *dev)
> if (!save_state)
> return;
>
> - cap = (u16 *)&save_state->cap.data[0];
> - pci_write_config_word(dev, ptm + PCI_PTM_CTRL, *cap);
> + cap = (u32 *)&save_state->cap.data[0];
> + pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, *cap);
> }
>
> /*
> @@ -112,7 +112,7 @@ void pci_ptm_init(struct pci_dev *dev)
> return;
>
> dev->ptm_cap = ptm;
> - pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_PTM, sizeof(u16));
> + pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_PTM, sizeof(u32));
>
> pci_read_config_dword(dev, ptm + PCI_PTM_CAP, &cap);
> dev->ptm_granularity = (cap & PCI_PTM_GRANULARITY_MASK) >> 8;
> @@ -170,7 +170,10 @@ static int __pci_enable_ptm(struct pci_dev *dev)
> return -EINVAL;
> }
>
> - ctrl = PCI_PTM_CTRL_ENABLE;
> + pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, &ctrl);
> +
> + ctrl |= PCI_PTM_CTRL_ENABLE;
> + ctrl &= ~PCI_PTM_GRANULARITY_MASK;
> ctrl |= dev->ptm_granularity << 8;
> if (dev->ptm_root)
> ctrl |= PCI_PTM_CTRL_ROOT;

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer