From: Frank Li <Frank.li@nxp.com>
To: cassel@kernel.org, "Krzysztof Wilczyński" <kwilczynski@kernel.org>
Cc: bhelgaas@google.com, gustavo.pimentel@synopsys.com,
helgaas@kernel.org, imx@lists.linux.dev, jdmason@kudzu.us,
jingoohan1@gmail.com, kw@linux.com, linux-kernel@vger.kernel.org,
linux-pci@vger.kernel.org, lpieralisi@kernel.org,
mani@kernel.org, robh@kernel.org
Subject: Re: [PATCH v4 1/1] PCI: dwc: Fix index 0 incorrectly being interpreted as a free ATU slot
Date: Fri, 3 May 2024 10:23:16 -0400 [thread overview]
Message-ID: <ZjTzVNWAkNDJC3cs@lizhi-Precision-Tower-5810> (raw)
In-Reply-To: <20240412160841.925927-1-Frank.Li@nxp.com>
On Fri, Apr 12, 2024 at 12:08:41PM -0400, Frank Li wrote:
> When PERST# assert and deassert happens on the PERST# supported platforms,
> the both iATU0 and iATU6 will map inbound window to BAR0. DMA will access
> to the area that was previously allocated (iATU0) for BAR0, instead of the
> new area (iATU6) for BAR0.
>
> Right now, we dodge the bullet because both iATU0 and iATU6 should
> currently translate inbound accesses to BAR0 to the same allocated memory
> area. However, having two separate inbound mappings for the same BAR is a
> disaster waiting to happen.
>
> The mapping between PCI BAR and iATU inbound window are maintained in the
> dw_pcie_ep::bar_to_atu[] array. While allocating a new inbound iATU map for
> a BAR, dw_pcie_ep_inbound_atu() API will first check for the availability
> of the existing mapping in the array and if it is not found (i.e., value in
> the array indexed by the BAR is found to be 0), then it will allocate a new
> map value using find_first_zero_bit().
>
> The issue here is, the existing logic failed to consider the fact that the
> map value '0' is a valid value for BAR0. Because, find_first_zero_bit()
> will return '0' as the map value for BAR0 (note that it returns the first
> zero bit position).
>
> Due to this, when PERST# assert + deassert happens on the PERST# supported
> platforms, the inbound window allocation restarts from BAR0 and the
> existing logic to find the BAR mapping will return '6' for BAR0 instead of
> '0' due to the fact that it considers '0' as an invalid map value.
>
> So fix this issue by always incrementing the map value before assigning to
> bar_to_atu[] array and then decrementing it while fetching. This will make
> sure that the map value '0' always represents the invalid mapping."
>
> Reported-by: Niklas Cassel <Niklas.Cassel@wdc.com>
> Closes: https://lore.kernel.org/linux-pci/ZXsRp+Lzg3x%2Fnhk3@x1-carbon/
> Tested-by: Niklas Cassel <niklas.cassel@wdc.com>
> Fixes: 4284c88fff0e ("PCI: designware-ep: Allow pci_epc_set_bar() update inbound map address")
> Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
Anyone take care this patch? Krzysztof Wilczyński, Lorenzo?
Frank
>
> Notes:
> Change from v3 to v4
> - commit message add "Right now, we dodge..."
> - Add Reviewed-by: Manivannan Sadhasivam
>
> Change from v2 to v3
> - Add impact in commit message
> - Add mani's detail description
> - Fix Closes link
>
> Change from v1 to v2
> - update subject
> - use free_win + 1 solution
> - still leave MAX_IATU_IN as 256. I am not sure if there are platfrom have
> 256 ATU. Suppose it only use max 6 in current EP framework.
> - @Niklas, can you help test it. My platform become unstable today.
>
> drivers/pci/controller/dwc/pcie-designware-ep.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 5befed2dc02b7..ba932bafdb230 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -139,7 +139,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
> if (!ep->bar_to_atu[bar])
> free_win = find_first_zero_bit(ep->ib_window_map, pci->num_ib_windows);
> else
> - free_win = ep->bar_to_atu[bar];
> + free_win = ep->bar_to_atu[bar] - 1;
>
> if (free_win >= pci->num_ib_windows) {
> dev_err(pci->dev, "No free inbound window\n");
> @@ -153,7 +153,11 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
> return ret;
> }
>
> - ep->bar_to_atu[bar] = free_win;
> + /*
> + * Always increment free_win before assignment, since value 0 is used to identify
> + * unallocated mapping.
> + */
> + ep->bar_to_atu[bar] = free_win + 1;
> set_bit(free_win, ep->ib_window_map);
>
> return 0;
> @@ -190,7 +194,10 @@ static void dw_pcie_ep_clear_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct dw_pcie_ep *ep = epc_get_drvdata(epc);
> struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> enum pci_barno bar = epf_bar->barno;
> - u32 atu_index = ep->bar_to_atu[bar];
> + u32 atu_index = ep->bar_to_atu[bar] - 1;
> +
> + if (!ep->bar_to_atu[bar])
> + return;
>
> __dw_pcie_ep_reset_bar(pci, func_no, bar, epf_bar->flags);
>
> --
> 2.34.1
>
next prev parent reply other threads:[~2024-05-03 14:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 16:08 [PATCH v4 1/1] PCI: dwc: Fix index 0 incorrectly being interpreted as a free ATU slot Frank Li
2024-05-03 14:23 ` Frank Li [this message]
2024-05-17 17:06 ` Krzysztof Wilczyński
2024-05-21 10:16 ` Niklas Cassel
2024-05-21 14:14 ` Bjorn Helgaas
2024-05-21 14:19 ` Damien Le Moal
2024-05-21 14:50 ` Krzysztof Wilczyński
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