Re: [PATCH] PCI: dw-rockchip: Configure max payload size on host init

From: Niklas Cassel <cassel@kernel.org>
To: Hans Zhang <18255117159@163.com>, Bjorn Helgaas <helgaas@kernel.org>
Cc: Shawn Lin <shawn.lin@rock-chips.com>,
	lpieralisi@kernel.org, kw@linux.com, bhelgaas@google.com,
	heiko@sntech.de, manivannan.sadhasivam@linaro.org,
	robh@kernel.org, jingoohan1@gmail.com,
	thomas.richard@bootlin.com, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Subject: Re: [PATCH] PCI: dw-rockchip: Configure max payload size on host init
Date: Fri, 18 Apr 2025 16:55:13 +0200	[thread overview]
Message-ID: <225CC628-432C-4E88-AF2B-17C948B3790B@kernel.org> (raw)
In-Reply-To: <22720eef-f5a3-4e72-9c41-35335ec20f80@163.com>



On 18 April 2025 14:33:08 CEST, Hans Zhang <18255117159@163.com> wrote:
>
>Dear Bjorn,
>
>Thanks your for reply. Niklas and I attempted to modify the relevant logic in drivers/pci/probe.c and found that there was a lot of code judging the global variable pcie_bus_config. At present, there is no good method. I will keep trying.
>
>I wonder if you have any good suggestions? It seems that the code logic regarding pcie_bus_config is a little complicated and cannot be modified for the time being?


Hans,

If:

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 364fa2a514f8..2e1c92fdd577 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2983,6 +2983,13 @@ void pcie_bus_configure_settings(struct pci_bus *bus)
         if (!pci_is_pcie(bus->self))
                 return;
  +       /*
+        * Start off with DevCtl.MPS == DevCap.MPS, unless PCIE_BUS_TUNE_OFF.
+        * This might get overriden by a MPS strategy below.
+        */
+       if (pcie_bus_config != PCIE_BUS_TUNE_OFF)
+               smpss = pcie_get_mps(bus->self);
+
         /*
          * FIXME - Peer to peer DMA is possible, though the endpoint would need
          * to be aware of the MPS of the destination.  To work around this,



does not work, can't you modify the code slightly so that it works?

I haven't tried myself, but considering that it works when walking the bus, it seems that it should be possible to get something working.


Kind regards,
Niklas

_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip
