Re: [PATCH 2/8] pci: pci_mvebu: Fix read_config() with PCI_SIZE_8 or PCI_SIZE_16

Stefan Roese
2021-11-02T10:45:23Z

> When reading 8 or 16 bits from config space, use appropriate readb() or
> readw() calls. This ensures that PCIe controller does not read more bits
> from endpoint card as asked by read_config() function.
>
> Technically there should not be an issue with reading data from config
> space which are not later used as there are no clear-by-read registers.
> But it is better to use correct read operation based on requested size.
>
> Signed-off-by: Pali Rohár <pali@kernel.org>
> Reviewed-by: Marek Behún <marek.behun@nic.cz>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

> ---
> drivers/pci/pci_mvebu.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci_mvebu.c b/drivers/pci/pci_mvebu.c
> index 8175511514ab..3991086e0d29 100644
> --- a/drivers/pci/pci_mvebu.c
> +++ b/drivers/pci/pci_mvebu.c
> @@ -184,9 +184,22 @@ static int mvebu_pcie_read_config(const struct udevice *bus, pci_dev_t bdf,
> writel(PCIE_CONF_ADDR(bdf, offset), pcie->base + PCIE_CONF_ADDR_OFF);
>
> /* read data */
> - data = readl(pcie->base + PCIE_CONF_DATA_OFF);
> + switch (size) {
> + case PCI_SIZE_8:
> + data = readb(pcie->base + PCIE_CONF_DATA_OFF + (offset & 3));
> + break;
> + case PCI_SIZE_16:
> + data = readw(pcie->base + PCIE_CONF_DATA_OFF + (offset & 2));
> + break;
> + case PCI_SIZE_32:
> + data = readl(pcie->base + PCIE_CONF_DATA_OFF);
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> debug("(addr,size,val)=(0x%04x, %d, 0x%08x)\n", offset, size, data);
> - *valuep = pci_conv_32_to_size(data, offset, size);
> + *valuep = data;
>
> return 0;
> }
>

Viele Grüße,
Stefan

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