linux-kernel - Re: [PATCH] PCI: keystone: Add workaround for Errata #i2037 (AM65x SR 1.0)

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Message-ID: <a0f50d92-defa-4241-9128-5d016f5915de@siemens.com>
Date: Thu, 27 Jun 2024 15:29:23 +0200
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Siddharth Vadapalli <s-vadapalli@...com>,
 Krzysztof Wilczyński <kw@...ux.com>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>, Rob Herring <robh@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Kishon Vijay Abraham I <kishon@...nel.org>,
 Vignesh Raghavendra <vigneshr@...com>, Nishanth Menon <nm@...com>,
 "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] PCI: keystone: Add workaround for Errata #i2037 (AM65x SR
 1.0)

On 27.06.24 14:24, Siddharth Vadapalli wrote:
> On Wed, Jun 26, 2024 at 12:10:41AM +0200, Jan Kiszka wrote:
>> From: Kishon Vijay Abraham I <kishon@...com>
>>
>> Errata #i2037 in AM65x/DRA80xM Processors Silicon Revision 1.0
>> (SPRZ452D_July 2018_Revised December 2019 [1]) mentions when an
>> inbound PCIe TLP spans more than two internal AXI 128-byte bursts,
>> the bus may corrupt the packet payload and the corrupt data may
>> cause associated applications or the processor to hang.
>>
>> The workaround for Errata #i2037 is to limit the maximum read
>> request size and maximum payload size to 128 Bytes. Add workaround
>> for Errata #i2037 here. The errata and workaround is applicable
>> only to AM65x SR 1.0 and later versions of the silicon will have
>> this fixed.
>>
>> [1] -> http://www.ti.com/lit/er/sprz452d/sprz452d.pdf
>>
>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>> Signed-off-by: Achal Verma <a-verma1@...com>
>> Link: https://lore.kernel.org/linux-pci/20210325090026.8843-7-kishon@ti.com/
> 
> Please drop the above. It needs to be mentioned as the v1 below the
> tear-line.
> 
>> Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
>> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
>> ---
>>
>> Needed for the IOT2050 PG1 variants. Pending downstream way too long.
>>
>>  drivers/pci/controller/dwc/pci-keystone.c | 42 +++++++++++++++++++++++
>>  1 file changed, 42 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
>> index d3a7d14ee685..a04f1087ce91 100644
>> --- a/drivers/pci/controller/dwc/pci-keystone.c
>> +++ b/drivers/pci/controller/dwc/pci-keystone.c
>> @@ -34,6 +34,11 @@
>>  #define PCIE_DEVICEID_SHIFT	16
> 
> [...]
> 
>>  
>> +	static const struct pci_device_id am6_pci_devids[] = {
>> +		{ PCI_DEVICE(PCI_VENDOR_ID_TI, PCI_DEVICE_ID_TI_AM654X),
>> +		 .class = PCI_CLASS_BRIDGE_PCI << 8, .class_mask = ~0, },
>> +		{ 0, },
>> +	};
>>  
>>  	if (pci_is_root_bus(bus))
>>  		bridge = dev;
>> @@ -562,6 +578,32 @@ static void ks_pcie_quirk(struct pci_dev *dev)
>>  			pcie_set_readrq(dev, 256);
>>  		}
>>  	}
>> +
>> +	/*
>> +	 * Memory transactions fail with PCI controller in AM654 PG1.0
>> +	 * when MRRS is set to more than 128 Bytes. Force the MRRS to
>> +	 * 128 Bytes in all downstream devices.
>> +	 */
> 
> Comments on the v1 patch at:
> https://lore.kernel.org/linux-pci/YF2K6+R1P3SNUoo5@rocinante/
> haven't been addressed in this patch. Kindly update the patch based on
> Krzysztof's feedback on the v1 patch.
> 

Oops, I didn't even realized that the link above pointed here - let me
fix this up quickly.

Jan

>> +	if (pci_match_id(am6_pci_devids, bridge)) {
>> +		bridge_dev = pci_get_host_bridge_device(dev);
>> +		if (!bridge_dev && !bridge_dev->parent)
>> +			return;
>> +
>> +		ks_pcie = dev_get_drvdata(bridge_dev->parent);
>> +		if (!ks_pcie)
>> +			return;
>> +
>> +		val = ks_pcie_app_readl(ks_pcie, PID);
>> +		val &= RTL;
>> +		val >>= RTL_SHIFT;
>> +		if (val != AM6_PCI_PG1_RTL_VER)
>> +			return;
>> +
>> +		if (pcie_get_readrq(dev) > 128) {
>> +			dev_info(&dev->dev, "limiting MRRS to 128\n");
>> +			pcie_set_readrq(dev, 128);
>> +		}
>> +	}
>>  }
>>  DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, ks_pcie_quirk);
> 
> Regards,
> Siddharth.

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