linux-kernel - Re: [PATCH v2] PCI: endpoint: pci-epf-test: Limit PCIe BAR size for fixed BARs

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Message-ID: <aLrXQGzYBB8JVE0Z@ryzen>
Date: Fri, 5 Sep 2025 14:27:44 +0200
From: Niklas Cassel <cassel@...nel.org>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>
Cc: linux-pci@...r.kernel.org,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Damien Le Moal <dlemoal@...nel.org>, Frank Li <Frank.Li@....com>,
	Jerome Brunet <jbrunet@...libre.com>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Wang Jiang <jiangwang@...inos.cn>, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2] PCI: endpoint: pci-epf-test: Limit PCIe BAR size for
 fixed BARs

On Fri, Sep 05, 2025 at 02:12:43PM +0200, Marek Vasut wrote:
> Currently, the test allocates BAR sizes according to fixed table
> bar_size[] = { 512, 512, 1024, 16384, 131072, 1048576 } . This
> does not work with controllers which have fixed size BARs, like
> Renesas R-Car V4H PCIe controller, which has BAR4 size limited
> to 256 Bytes, which is much less than 131072 currently requested
> by this test.

Perhaps rephase this to more clearly state that:
This does not work with controllers with have fixed size BARs that is
smaller than the requested BAR size.

(Since a lot of controllers drivers in-tree have fixed size BARs,
and they do work perfectly fine, but it is only because their fixed
size is larger than the size requested by pci-epf-test.c)


> 
> Adjust the test such, that in case a fixed size BAR is detected
> on a controller, minimum of requested size and fixed size BAR
> size is used during the test instead.

This sentence needs to be updated, since you no longer take the minimum
of requested size and fixed size BAR.

Perhaps simply:
"Adjust the test such that in case a fixed size BAR is detected,
the fixed BAR size is used, as that is the only possibly option."


With that:
Reviewed-by: Niklas Cassel <cassel@...nel.org>


> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index e091193bd8a8a..2418add64104a 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -1050,7 +1050,12 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
>  		if (bar == test_reg_bar)
>  			continue;
>  
> -		base = pci_epf_alloc_space(epf, bar_size[bar], bar,
> +		if (epc_features->bar[bar].type == BAR_FIXED)
> +			test_reg_size = epc_features->bar[bar].fixed_size;
> +		else
> +			test_reg_size = bar_size[bar];
> +
> +		base = pci_epf_alloc_space(epf, test_reg_size, bar,
>  					   epc_features, PRIMARY_INTERFACE);
>  		if (!base)
>  			dev_err(dev, "Failed to allocate space for BAR%d\n",
> -- 
> 2.50.1
>