linux-kernel - Re: [PATCH v2] PCI: keystone: Fix ks_pcie_v3_65_add

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Date:   Wed, 18 Oct 2023 13:49:26 +0530
From:   Ravi Gunasekaran <r-gunasekaran@...com>
To:     Siddharth Vadapalli <s-vadapalli@...com>, <lpieralisi@...nel.org>,
        <robh@...nel.org>, <kw@...ux.com>, <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>
Subject: Re: [PATCH v2] PCI: keystone: Fix ks_pcie_v3_65_add_bus() for AM654x
 SoC

Siddharth,


On 10/18/23 1:20 PM, 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")

6ab15b5e7057 (PCI: dwc: keystone: Convert .scan_bus() callback to use add_bus)
is that one that seems to have introduced this issue. 

ks_pcie_v3_65_scan_bus() was for IP version 3.65 and this was renamed and
added to "ks_pcie_ops" which is used by other IP versions as well.


> 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.
> 
> Regards,
> Siddharth.
> 
>  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 */

-- 
Regards,
Ravi