linux-kernel - Re: [PATCH v3 1/3] PCI: endpoint: Handle 64-bit BARs properly

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Message-ID: <20180228142148.GD21854@e107981-ln.cambridge.arm.com>
Date:   Wed, 28 Feb 2018 14:21:48 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Niklas Cassel <niklas.cassel@...s.com>
Cc:     kishon@...com, Bjorn Helgaas <bhelgaas@...gle.com>,
        Sekhar Nori <nsekhar@...com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Cyrille Pitchen <cyrille.pitchen@...e-electrons.com>,
        Niklas Cassel <niklass@...s.com>,
        John Keeping <john@...anate.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] PCI: endpoint: Handle 64-bit BARs properly

On Tue, Feb 27, 2018 at 12:59:05PM +0100, Niklas Cassel wrote:
> A 64-bit BAR uses the succeeding BAR for the upper bits, therefore
> we cannot call pci_epc_set_bar() on a BAR that follows a 64-bit BAR.
> 
> If pci_epc_set_bar() is called with flag PCI_BASE_ADDRESS_MEM_TYPE_64,

PCI_BASE_ADDRESS_MEM_TYPE_64 is detected through a sizeof(dma_addr_t).

I thought we decided to describe the BARs not as dma_addr_t + size but
as resources, which would allow you to have flags describing their
actual size.

Current code has a fixed BAR size defined by the dma_addr_t type size
and I do not think that's what we really want.

How is (in HW I mean) actually the BAR size configured in a given EPF ?

Thanks,
Lorenzo

> it has to be up to the controller driver to write both BAR[x] and BAR[x+1]
> (and BAR_mask[x] and BAR_mask[x+1]).
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@...s.com>
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 64d8a17f8094..ecbf6a7750dc 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -382,6 +382,8 @@ static int pci_epf_test_set_bar(struct pci_epf *epf)
>  			if (bar == test_reg_bar)
>  				return ret;
>  		}
> +		if (flags & PCI_BASE_ADDRESS_MEM_TYPE_64)
> +			bar++;
>  	}
>  
>  	return 0;
> -- 
> 2.14.2
>