Message-ID: <20231018163632.GA1364574@bhelgaas>
Date:   Wed, 18 Oct 2023 11:36:32 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Siddharth Vadapalli <s-vadapalli@...com>
Cc:     lpieralisi@...nel.org, robh@...nel.org, kw@...ux.com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        r-gunasekaran@...com, srk@...com,
        Serge Semin <fancer.lancer@...il.com>
Subject: Re: [PATCH v2] PCI: keystone: Fix ks_pcie_v3_65_add_bus() for AM654x
 SoC

[+cc Serge (please cc people who have commented on previous revisions)]

On Wed, Oct 18, 2023 at 01:20:38PM +0530, Siddharth Vadapalli wrote:
> The ks_pcie_v3_65_add_bus() member of "ks_pcie_ops" was added for
> platforms using DW PCIe IP-core version 3.65a. The AM654x SoC uses
> DW PCIe IP-core version 4.90a and ks_pcie_v3_65_add_bus() is not
> applicable to it.
> 
> The commit which added support for the AM654x SoC has reused majority
> of the functions with the help of the "is_am6" flag to handle AM654x
> separately where applicable. Thus, make use of the "is_am6" flag and
> change ks_pcie_v3_65_add_bus() to no-op for AM654x SoC.
> 
> Fixes: 18b0415bc802 ("PCI: keystone: Add support for PCIe RC in AM654x Platforms")
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
> ---
> Hello,
> 
> This patch is based on linux-next tagged next-20231018.
> 
> The v1 of this patch is at:
> https://lore.kernel.org/r/20231011123451.34827-1-s-vadapalli@ti.com/
> 
> While there are a lot of changes since v1 and this patch could have been
> posted as a v1 patch itself, I decided to post it as the v2 of the patch
> mentioned above since it aims to address the issue described by the v1
> patch and is similar in that sense. However, the solution to the issue
> described in the v1 patch appears to be completely different from what
> was implemented in the v1 patch. Thus, the commit message and subject of
> this patch have been modified accordingly.
> 
> Changes since v1:
> - Updated patch subject and commit message.
> - Determined that issue is not with the absence of Link as mentioned in
>   v1 patch. Even with Link up and endpoint device connected, if
>   ks_pcie_v3_65_add_bus() is invoked and executed, all reads to the
>   MSI-X offsets return 0xffffffff when pcieport driver attempts to setup
>   AER and PME services. The all Fs return value indicates that the MSI-X
>   configuration is failing even if Endpoint device is connected. This is
>   because the ks_pcie_v3_65_add_bus() function is not applicable to the
>   AM654x SoC which uses DW PCIe IP-core version 4.90a.

Thanks for verifying that this doesn't actually depend on whether the
link is up.

I think that means we should be able to get rid of the
ks_pcie_v3_65_add_bus() callback altogether and instead do this along
with the rest of the Root Port init.

>  drivers/pci/controller/dwc/pci-keystone.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
> index 0def919f89fa..3abd59335574 100644
> --- a/drivers/pci/controller/dwc/pci-keystone.c
> +++ b/drivers/pci/controller/dwc/pci-keystone.c
> @@ -459,7 +459,7 @@ static int ks_pcie_v3_65_add_bus(struct pci_bus *bus)
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>  	struct keystone_pcie *ks_pcie = to_keystone_pcie(pci);
>  
> -	if (!pci_is_root_bus(bus))
> +	if (!pci_is_root_bus(bus) || ks_pcie->is_am6)
>  		return 0;
>  
>  	/* Configure and set up BAR0 */
> -- 
> 2.34.1
> 
> 
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