On Fri, Feb 23, 2024 at 07:33:38PM +0530, Mrinmay Sarkar wrote:
Subject should be:
"PCI: qcom: Override NO_SNOOP attribute for SA8775P"
> Due to some hardware changes, SA8775P has set the NO_SNOOP attribute
> in its TLP for all the PCIe controllers. NO_SNOOP attribute when set,
> the requester is indicating that there no cache coherency issues exit
> for the addressed memory on the host i.e., memory is not cached. But
s/host/endpoint
> in reality, requester cannot assume this unless there is a complete
> control/visibility over the addressed memory on the host.
>
s/host/endpoint
> And worst case, if the memory is cached on the host, it may lead to
s/host/endpoint
> memory corruption issues. It should be noted that the caching of memory
> on the host is not solely dependent on the NO_SNOOP attribute in TLP.
>
s/host/endpoint
> So to avoid the corruption, this patch overrides the NO_SNOOP attribute
> by setting the PCIE_PARF_NO_SNOOP_OVERIDE register. This patch is not
> needed for other upstream supported platforms since they do not set
> NO_SNOOP attribute by default.
>
> 8775 has IP version 1.34.0 so intruduce a new cfg(cfg_1_34_0) for this
> platform. Assign enable_cache_snoop flag into struct qcom_pcie_cfg and
> set it true in cfg_1_34_0 and enable cache snooping if this particular
> flag is true.
>
> Signed-off-by: Mrinmay Sarkar <quic_msarkar@xxxxxxxxxxx>
> ---
> drivers/pci/controller/dwc/pcie-qcom.c | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 2ce2a3bd932b..872be7f7d7b3 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -51,6 +51,7 @@
> #define PARF_SID_OFFSET 0x234
> #define PARF_BDF_TRANSLATE_CFG 0x24c
> #define PARF_SLV_ADDR_SPACE_SIZE 0x358
> +#define PARF_NO_SNOOP_OVERIDE 0x3d4
> #define PARF_DEVICE_TYPE 0x1000
> #define PARF_BDF_TO_SID_TABLE_N 0x2000
>
> @@ -117,6 +118,10 @@
> /* PARF_LTSSM register fields */
> #define LTSSM_EN BIT(8)
>
> +/* PARF_NO_SNOOP_OVERIDE register fields */
> +#define WR_NO_SNOOP_OVERIDE_EN BIT(1)
> +#define RD_NO_SNOOP_OVERIDE_EN BIT(3)
> +
> /* PARF_DEVICE_TYPE register fields */
> #define DEVICE_TYPE_RC 0x4
>
> @@ -229,6 +234,7 @@ struct qcom_pcie_ops {
>
Please add Kdoc comments for this struct. And describe the "override_no_snoop"
member as below:
"Override NO_SNOOP attribute in TLP to enable cache snooping"
> struct qcom_pcie_cfg {
> const struct qcom_pcie_ops *ops;
> + bool enable_cache_snoop;
Rename this to "override_no_snoop"
> };
>
> struct qcom_pcie {
> @@ -961,6 +967,13 @@ static int qcom_pcie_init_2_7_0(struct qcom_pcie *pcie)
>
> static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie)
> {
> + const struct qcom_pcie_cfg *pcie_cfg = pcie->cfg;
> +
> + /* Enable cache snooping for SA8775P */
Remove this comment in favor of Kdoc mentioned above.
- Mani
--
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