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SubjectRe: [PATCH] PCI: designware-ep: Fix ->get_msi() to check MSI_EN bit
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Hi Lorenzo,

On Wednesday 22 November 2017 05:07 PM, Lorenzo Pieralisi wrote:
> 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

MSI address is written in the MSI capabiltiy register by the host.
>
> Where is the address set ?
>
>> thinks host supports MSI.
>
> Add a Fixes: tag please.

sure.
>
>> 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.

IIUC the host will write to these registers in __pci_write_msi_msg using the
configuration writes.
>
> 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.

Do you mean dw_pcie_ep_set_msi can overwrite MSI_CAP_MSI_EN and we should avoid
that?

Thanks
Kishon

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