On Thu, Oct 29, 2020 at 11:09:59AM +0530, Vidya Sagar wrote: > DesignWare core has a TLP digest (TD) override bit in one of the control > registers of ATU. This bit also needs to be programmed for proper ECRC > functionality. This is currently identified as an issue with DesignWare > IP version 4.90a. This patch does the required programming in ATU upon > querying the system policy for ECRC.
I guess this is a hardware defect, right? How much of a problem would it be if we instead added a "no_ecrc" quirk for this hardware so we never enabled ECRC? IIUC, the current Linux support of ECRC is a single choice at boot-time: by default ECRC is not enabled, but if you boot with "pci=ecrc=on", we turn on ECRC for every device. That seems like the minimal support, but I think the spec allows ECRC to be enabled selectively, on individual devices. I can imagine a sysfs knob that would allow us to enable/disable ECRC per-device at run-time. If we had such a sysfs knob, it would be pretty ugly and maybe impractical to work around this hardware issue. So I'm a little bit hesitant to add functionality that might have to be removed in the future. > Signed-off-by: Vidya Sagar <[email protected]> > Reviewed-by: Jingoo Han <[email protected]> > --- > V3: > * Added 'Reviewed-by: Jingoo Han <[email protected]>' > > V2: > * Addressed Jingoo's review comment > * Removed saving 'td' bit information in 'dw_pcie' structure > > drivers/pci/controller/dwc/pcie-designware.c | 8 ++++++-- > drivers/pci/controller/dwc/pcie-designware.h | 1 + > 2 files changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c > b/drivers/pci/controller/dwc/pcie-designware.c > index b5e438b70cd5..cbd651b219d2 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.c > +++ b/drivers/pci/controller/dwc/pcie-designware.c > @@ -246,6 +246,8 @@ static void dw_pcie_prog_outbound_atu_unroll(struct > dw_pcie *pci, u8 func_no, > dw_pcie_writel_ob_unroll(pci, index, PCIE_ATU_UNR_UPPER_TARGET, > upper_32_bits(pci_addr)); > val = type | PCIE_ATU_FUNC_NUM(func_no); > + if (pci->version == 0x490A) > + val = val | pcie_is_ecrc_enabled() << PCIE_ATU_TD_SHIFT; > val = upper_32_bits(size - 1) ? > val | PCIE_ATU_INCREASE_REGION_SIZE : val; > dw_pcie_writel_ob_unroll(pci, index, PCIE_ATU_UNR_REGION_CTRL1, val); > @@ -294,8 +296,10 @@ static void __dw_pcie_prog_outbound_atu(struct dw_pcie > *pci, u8 func_no, > lower_32_bits(pci_addr)); > dw_pcie_writel_dbi(pci, PCIE_ATU_UPPER_TARGET, > upper_32_bits(pci_addr)); > - dw_pcie_writel_dbi(pci, PCIE_ATU_CR1, type | > - PCIE_ATU_FUNC_NUM(func_no)); > + val = type | PCIE_ATU_FUNC_NUM(func_no); > + if (pci->version == 0x490A) > + val = val | pcie_is_ecrc_enabled() << PCIE_ATU_TD_SHIFT; > + dw_pcie_writel_dbi(pci, PCIE_ATU_CR1, val); > dw_pcie_writel_dbi(pci, PCIE_ATU_CR2, PCIE_ATU_ENABLE); > > /* > diff --git a/drivers/pci/controller/dwc/pcie-designware.h > b/drivers/pci/controller/dwc/pcie-designware.h > index e7f441441db2..b01ef407fd52 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -89,6 +89,7 @@ > #define PCIE_ATU_TYPE_IO 0x2 > #define PCIE_ATU_TYPE_CFG0 0x4 > #define PCIE_ATU_TYPE_CFG1 0x5 > +#define PCIE_ATU_TD_SHIFT 8 > #define PCIE_ATU_FUNC_NUM(pf) ((pf) << 20) > #define PCIE_ATU_CR2 0x908 > #define PCIE_ATU_ENABLE BIT(31) > -- > 2.17.1 >
