Re: [PATCH v2 01/10] memory: tegra: Implement SID override programming

[Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>]

On 20/04/2021 19:26, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> Instead of programming all SID overrides during early boot, perform the
> operation on-demand after the SMMU translations have been set up for a
> device. This reuses data from device tree to match memory clients for a
> device and programs the SID specified in device tree, which corresponds
> to the SID used for the SMMU context banks for the device.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
>  drivers/memory/tegra/mc.c       |  9 +++++
>  drivers/memory/tegra/tegra186.c | 72 +++++++++++++++++++++++++++++++++
>  include/soc/tegra/mc.h          |  3 ++
>  3 files changed, 84 insertions(+)
> 
> diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
> index c854639cf30c..bace5ecfe770 100644
> --- a/drivers/memory/tegra/mc.c
> +++ b/drivers/memory/tegra/mc.c
> @@ -97,6 +97,15 @@ struct tegra_mc *devm_tegra_memory_controller_get(struct device *dev)
>  }
>  EXPORT_SYMBOL_GPL(devm_tegra_memory_controller_get);
>  
> +int tegra_mc_probe_device(struct tegra_mc *mc, struct device *dev)
> +{
> +	if (mc->soc->ops && mc->soc->ops->probe_device)
> +		return mc->soc->ops->probe_device(mc, dev);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(tegra_mc_probe_device);
> +
>  static int tegra_mc_block_dma_common(struct tegra_mc *mc,
>  				     const struct tegra_mc_reset *rst)
>  {
> diff --git a/drivers/memory/tegra/tegra186.c b/drivers/memory/tegra/tegra186.c
> index 1f87915ccd62..e65eac5764d4 100644
> --- a/drivers/memory/tegra/tegra186.c
> +++ b/drivers/memory/tegra/tegra186.c
> @@ -4,6 +4,7 @@
>   */
>  
>  #include <linux/io.h>
> +#include <linux/iommu.h>
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/of_device.h>
> @@ -15,6 +16,10 @@
>  #include <dt-bindings/memory/tegra186-mc.h>
>  #endif
>  
> +#define MC_SID_STREAMID_OVERRIDE_MASK GENMASK(7, 0)
> +#define MC_SID_STREAMID_SECURITY_WRITE_ACCESS_DISABLED BIT(16)
> +#define MC_SID_STREAMID_SECURITY_OVERRIDE BIT(8)
> +
>  static void tegra186_mc_program_sid(struct tegra_mc *mc)
>  {
>  	unsigned int i;
> @@ -66,10 +71,77 @@ static int tegra186_mc_resume(struct tegra_mc *mc)
>  	return 0;
>  }
>  
> +static void tegra186_mc_client_sid_override(struct tegra_mc *mc,
> +					    const struct tegra_mc_client *client,
> +					    unsigned int sid)
> +{
> +	u32 value, old;
> +
> +	value = readl(mc->regs + client->regs.sid.security);
> +	if ((value & MC_SID_STREAMID_SECURITY_OVERRIDE) == 0) {
> +		/*
> +		 * If the secure firmware has locked this down the override
> +		 * for this memory client, there's nothing we can do here.
> +		 */
> +		if (value & MC_SID_STREAMID_SECURITY_WRITE_ACCESS_DISABLED)
> +			return;
> +
> +		/*
> +		 * Otherwise, try to set the override itself. Typically the
> +		 * secure firmware will never have set this configuration.
> +		 * Instead, it will either have disabled write access to
> +		 * this field, or it will already have set an explicit
> +		 * override itself.
> +		 */
> +		WARN_ON((value & MC_SID_STREAMID_SECURITY_OVERRIDE) == 0);
> +
> +		value |= MC_SID_STREAMID_SECURITY_OVERRIDE;
> +		writel(value, mc->regs + client->regs.sid.security);
> +	}
> +
> +	value = readl(mc->regs + client->regs.sid.override);
> +	old = value & MC_SID_STREAMID_OVERRIDE_MASK;
> +
> +	if (old != sid) {
> +		dev_dbg(mc->dev, "overriding SID %x for %s with %x\n", old,
> +			client->name, sid);
> +		writel(sid, mc->regs + client->regs.sid.override);
> +	}
> +}
> +
> +static int tegra186_mc_probe_device(struct tegra_mc *mc, struct device *dev)
> +{
> +#if IS_ENABLED(CONFIG_IOMMU_API)

Is this part really build-time dependent? I don't see here any uses of
IOMMU specific fields, so maybe this should be runtime choice based on
enabled interconnect devices?

> +	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> +	struct of_phandle_args args;
> +	unsigned int i, index = 0;
> +
> +	while (!of_parse_phandle_with_args(dev->of_node, "interconnects", "#interconnect-cells",
> +					   index, &args)) {
> +		if (args.np == mc->dev->of_node && args.args_count != 0) {
> +			for (i = 0; i < mc->soc->num_clients; i++) {
> +				const struct tegra_mc_client *client = &mc->soc->clients[i];
> +
> +				if (client->id == args.args[0]) {
> +					u32 sid = fwspec->ids[0] & MC_SID_STREAMID_OVERRIDE_MASK;
> +
> +					tegra186_mc_client_sid_override(mc, client, sid);
> +				}
> +			}
> +		}
> +
> +		index++;
> +	}
> +#endif
> +
> +	return 0;
> +}
> +
>  const struct tegra_mc_ops tegra186_mc_ops = {
>  	.probe = tegra186_mc_probe,
>  	.remove = tegra186_mc_remove,
>  	.resume = tegra186_mc_resume,
> +	.probe_device = tegra186_mc_probe_device,
>  };
>  
>  #if defined(CONFIG_ARCH_TEGRA_186_SOC)
> diff --git a/include/soc/tegra/mc.h b/include/soc/tegra/mc.h
> index 1387747d574b..bbad6330008b 100644
> --- a/include/soc/tegra/mc.h
> +++ b/include/soc/tegra/mc.h
> @@ -176,6 +176,7 @@ struct tegra_mc_ops {
>  	int (*suspend)(struct tegra_mc *mc);
>  	int (*resume)(struct tegra_mc *mc);
>  	irqreturn_t (*handle_irq)(int irq, void *data);
> +	int (*probe_device)(struct tegra_mc *mc, struct device *dev);
>  };
>  
>  struct tegra_mc_soc {
> @@ -240,4 +241,6 @@ devm_tegra_memory_controller_get(struct device *dev)
>  }
>  #endif
>  
> +int tegra_mc_probe_device(struct tegra_mc *mc, struct device *dev);
> +

What about !CONFIG_TEGRA_MC? I think arm-smmmu will fail.

>  #endif /* __SOC_TEGRA_MC_H__ */
> 


Best regards,
Krzysztof

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