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SubjectRe: [PATCH] PCI: designware-ep: Fix ->get_msi() to check MSI_EN bit
On Wed, Nov 22, 2017 at 02:34:27PM +0530, Kishon Vijay Abraham I wrote:
> ->get_msi() now checks MSI_EN bit in the MSI CAPABILITY register to
> find whether the host supports MSI instead of using the
> MSI ADDRESS in the MSI CAPABILITY register.

I think that's a sensible thing to do regardless, given that I do not
understand why 0x0 can't be a valid MSI address in the first place.

> This fixes the issue with the following sequence
> 'modprobe pci_endpoint_test' enables MSI
> 'rmmod pci_endpoint_test' disables MSI but MSI address has a valid value
> 'modprobe pci_endpoint_test no_msi=1' - Since MSI address has a valid
> value (set during the previous insertion of the module), EP

Where is the address set ?

> thinks host supports MSI.

Add a Fixes: tag please.

> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
> drivers/pci/dwc/pcie-designware-ep.c | 12 +++---------
> drivers/pci/dwc/pcie-designware.h | 1 +
> 2 files changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
> index d53d5f168363..7c621877a939 100644
> --- a/drivers/pci/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/dwc/pcie-designware-ep.c
> @@ -197,20 +197,14 @@ static int dw_pcie_ep_map_addr(struct pci_epc *epc, phys_addr_t addr,
> static int dw_pcie_ep_get_msi(struct pci_epc *epc)
> {
> int val;
> - u32 lower_addr;
> - u32 upper_addr;
> struct dw_pcie_ep *ep = epc_get_drvdata(epc);
> struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>
> - val = dw_pcie_readb_dbi(pci, MSI_MESSAGE_CONTROL);
> - val = (val & MSI_CAP_MME_MASK) >> MSI_CAP_MME_SHIFT;
> -
> - lower_addr = dw_pcie_readl_dbi(pci, MSI_MESSAGE_ADDR_L32);
> - upper_addr = dw_pcie_readl_dbi(pci, MSI_MESSAGE_ADDR_U32);

I can't find code that writes these registers, see above for my
question.

On top of that I think that what's done the EPF test function driver in
struct pci_epf.bind() should be undone in struct pci_epf.unbind() and I
do not think that's happening for MSIs.

> -
> - if (!(lower_addr || upper_addr))
> + val = dw_pcie_readw_dbi(pci, MSI_MESSAGE_CONTROL);

MSI_MESSAGE_CONTROL is written in dw_pcie_ep_set_msi(), I assume a write
to bit[0] (ie MSI_CAP_MSI_EN_MASK) is ignored - it would be good if you
can clarify that as well please.

Thanks,
Lorenzo

> + if (!(val & MSI_CAP_MSI_EN_MASK))
> return -EINVAL;
>
> + val = (val & MSI_CAP_MME_MASK) >> MSI_CAP_MME_SHIFT;
> return val;
> }
>
> diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
> index e5d9d77b778e..cb493bcae8b4 100644
> --- a/drivers/pci/dwc/pcie-designware.h
> +++ b/drivers/pci/dwc/pcie-designware.h
> @@ -101,6 +101,7 @@
> #define MSI_MESSAGE_CONTROL 0x52
> #define MSI_CAP_MMC_SHIFT 1
> #define MSI_CAP_MME_SHIFT 4
> +#define MSI_CAP_MSI_EN_MASK 0x1
> #define MSI_CAP_MME_MASK (7 << MSI_CAP_MME_SHIFT)
> #define MSI_MESSAGE_ADDR_L32 0x54
> #define MSI_MESSAGE_ADDR_U32 0x58
> --
> 2.11.0
>

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