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

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Message-ID: <b3d5773d-c573-4491-b799-90405a8af6a9@kernel.org>
Date: Thu, 4 Sep 2025 11:40:15 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>, linux-pci@...r.kernel.org
Cc: Krzysztof Wilczyński <kwilczynski@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>, Frank Li <Frank.Li@....com>,
 Kishon Vijay Abraham I <kishon@...nel.org>,
 Manivannan Sadhasivam <mani@...nel.org>, Niklas Cassel <cassel@...nel.org>,
 Wang Jiang <jiangwang@...inos.cn>, linux-kernel@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] PCI: endpoint: pci-epf-test: Limit PCIe BAR size for
 fixed BARs

On 9/4/25 11:37 AM, 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.
> 
> 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 helps with test failures reported as follows:
> "
> pci_epf_test pci_epf_test.0: requested BAR size is larger than fixed size
> pci_epf_test pci_epf_test.0: Failed to allocate space for BAR4
> "
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>
> ---
> Cc: "Krzysztof Wilczyński" <kwilczynski@...nel.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Damien Le Moal <dlemoal@...nel.org>
> Cc: Frank Li <Frank.Li@....com>
> Cc: Kishon Vijay Abraham I <kishon@...nel.org>
> Cc: Manivannan Sadhasivam <mani@...nel.org>
> Cc: Niklas Cassel <cassel@...nel.org>
> Cc: Wang Jiang <jiangwang@...inos.cn>
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-pci@...r.kernel.org
> Cc: linux-renesas-soc@...r.kernel.org
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index e091193bd8a8a..d9c950d4c9a9e 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -1022,7 +1022,8 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
>  	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
>  	enum pci_barno bar;
>  	const struct pci_epc_features *epc_features = epf_test->epc_features;
> -	size_t test_reg_size;
> +	size_t test_reg_size, test_bar_size;
> +	u64 bar_fixed_size;
>  
>  	test_reg_bar_size = ALIGN(sizeof(struct pci_epf_test_reg), 128);
>  
> @@ -1050,7 +1051,13 @@ 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,
> +		test_bar_size = bar_size[bar];
> +
> +		bar_fixed_size = epc_features->bar[bar].fixed_size;
> +		if (epc_features->bar[bar].type == BAR_FIXED && bar_fixed_size)
> +			test_bar_size = min(bar_size[bar], bar_fixed_size);

I think this can be simplified to:

		if (epc_features->bar[bar].type == BAR_FIXED)
			test_bar_size = epc_features->bar[bar].fixed_size;
		else
			test_bar_size = bar_size[bar];

because if the bar type is BAR_FIXED, then the size of the bar can only be its
fixed size.

> +
> +		base = pci_epf_alloc_space(epf, test_bar_size, bar,
>  					   epc_features, PRIMARY_INTERFACE);
>  		if (!base)
>  			dev_err(dev, "Failed to allocate space for BAR%d\n",


-- 
Damien Le Moal
Western Digital Research