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    SubjectRe: [RFC 2/9] PCI: pci-bridge-emul: Eliminate reserved member
    [+cc Thomas, Russell]

    On Fri, Feb 07, 2020 at 05:00:00PM -0700, Jon Derrick wrote:
    > Assume any bit not in the Read-Only, Read-Write, or Write-1-to-Clear
    > behavior masks is a Reserved bit and should return 0 on reads.

    This also seems like it makes sense on its own, especially if you can
    include a spec citation.

    > Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
    > ---
    > drivers/pci/pci-bridge-emul.c | 28 +++++++++++-----------------
    > 1 file changed, 11 insertions(+), 17 deletions(-)
    >
    > diff --git a/drivers/pci/pci-bridge-emul.c b/drivers/pci/pci-bridge-emul.c
    > index d065c2a..e0567ca 100644
    > --- a/drivers/pci/pci-bridge-emul.c
    > +++ b/drivers/pci/pci-bridge-emul.c
    > @@ -24,6 +24,15 @@
    > #define PCI_CAP_PCIE_START PCI_BRIDGE_CONF_END
    > #define PCI_CAP_PCIE_END (PCI_CAP_PCIE_START + PCI_EXP_SLTSTA2 + 2)
    >
    > +/**
    > + * struct pci_bridge_reg_behavior - register bits behaviors
    > + * @ro: Read-Only bits
    > + * @rw: Read-Write bits
    > + * @w1c: Write-1-to-Clear bits
    > + *
    > + * Reads and Writes will be filtered by specified behavior. All other bits not
    > + * declared are assumed 'Reserved' and will return 0 on reads.
    > + */
    > struct pci_bridge_reg_behavior {
    > /* Read-only bits */
    > u32 ro;
    > @@ -33,9 +42,6 @@ struct pci_bridge_reg_behavior {
    >
    > /* Write-1-to-clear bits */
    > u32 w1c;
    > -
    > - /* Reserved bits (hardwired to 0) */
    > - u32 rsvd;
    > };
    >
    > static const struct pci_bridge_reg_behavior pci_regs_behavior[] = {
    > @@ -49,7 +55,6 @@ struct pci_bridge_reg_behavior {
    > PCI_COMMAND_FAST_BACK) |
    > (PCI_STATUS_CAP_LIST | PCI_STATUS_66MHZ |
    > PCI_STATUS_FAST_BACK | PCI_STATUS_DEVSEL_MASK) << 16),
    > - .rsvd = GENMASK(15, 10) | ((BIT(6) | GENMASK(3, 0)) << 16),
    > .w1c = (PCI_STATUS_PARITY |
    > PCI_STATUS_SIG_TARGET_ABORT |
    > PCI_STATUS_REC_TARGET_ABORT |
    > @@ -106,8 +111,6 @@ struct pci_bridge_reg_behavior {
    > PCI_STATUS_REC_MASTER_ABORT |
    > PCI_STATUS_SIG_SYSTEM_ERROR |
    > PCI_STATUS_DETECTED_PARITY) << 16,
    > -
    > - .rsvd = ((BIT(6) | GENMASK(4, 0)) << 16),
    > },
    >
    > [PCI_MEMORY_BASE / 4] = {
    > @@ -140,12 +143,10 @@ struct pci_bridge_reg_behavior {
    >
    > [PCI_CAPABILITY_LIST / 4] = {
    > .ro = GENMASK(7, 0),
    > - .rsvd = GENMASK(31, 8),
    > },
    >
    > [PCI_ROM_ADDRESS1 / 4] = {
    > .rw = GENMASK(31, 11) | BIT(0),
    > - .rsvd = GENMASK(10, 1),
    > },
    >
    > /*
    > @@ -168,8 +169,6 @@ struct pci_bridge_reg_behavior {
    > .ro = (GENMASK(15, 8) | ((PCI_BRIDGE_CTL_FAST_BACK) << 16)),
    >
    > .w1c = BIT(10) << 16,
    > -
    > - .rsvd = (GENMASK(15, 12) | BIT(4)) << 16,
    > },
    > };
    >
    > @@ -196,13 +195,11 @@ struct pci_bridge_reg_behavior {
    > */
    > .w1c = (BIT(6) | GENMASK(3, 0)) << 16,
    > .ro = GENMASK(5, 4) << 16,
    > - .rsvd = GENMASK(15, 7) << 16,
    > },
    >
    > [PCI_EXP_LNKCAP / 4] = {
    > /* All bits are RO, except bit 23 which is reserved */
    > .ro = lower_32_bits(~BIT(23)),
    > - .rsvd = BIT(23),
    > },
    >
    > [PCI_EXP_LNKCTL / 4] = {
    > @@ -216,7 +213,6 @@ struct pci_bridge_reg_behavior {
    > .rw = GENMASK(15, 14) | GENMASK(11, 3) | GENMASK(1, 0),
    > .ro = GENMASK(13, 0) << 16,
    > .w1c = GENMASK(15, 14) << 16,
    > - .rsvd = GENMASK(13, 12) | BIT(2),
    > },
    >
    > [PCI_EXP_SLTCAP / 4] = {
    > @@ -234,7 +230,6 @@ struct pci_bridge_reg_behavior {
    > .rw = GENMASK(14, 0),
    > .w1c = (BIT(8) | GENMASK(4, 0)) << 16,
    > .ro = GENMASK(7, 5) << 16,
    > - .rsvd = BIT(15) | (GENMASK(15, 9) << 16),
    > },
    >
    > [PCI_EXP_RTCTL / 4] = {
    > @@ -246,7 +241,6 @@ struct pci_bridge_reg_behavior {
    > */
    > .rw = GENMASK(4, 0),
    > .ro = BIT(0) << 16,
    > - .rsvd = GENMASK(15, 5) | (GENMASK(15, 1) << 16),
    > },
    >
    > [PCI_EXP_RTSTA / 4] = {
    > @@ -256,7 +250,6 @@ struct pci_bridge_reg_behavior {
    > */
    > .ro = BIT(17) | GENMASK(15, 0),
    > .w1c = BIT(16),
    > - .rsvd = GENMASK(31, 18),
    > },
    > };
    >
    > @@ -364,7 +357,8 @@ int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
    > * Make sure we never return any reserved bit with a value
    > * different from 0.
    > */
    > - *value &= ~behavior[reg / 4].rsvd;
    > + *value &= behavior[reg / 4].ro | behavior[reg / 4].rw |
    > + behavior[reg / 4].w1c;
    >
    > if (size == 1)
    > *value = (*value >> (8 * (where & 3))) & 0xff;
    > --
    > 1.8.3.1
    >

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