Re: [PATCH v4 28/37] memory: tegra: Register as interconnect provider

Georgi Djakov
2020-07-01T17:12:29Z

Hi Dmitry,

Thank you for updating the patches!

On 6/9/20 16:13, Dmitry Osipenko wrote:
> Now memory controller is a memory interconnection provider. This allows us
> to use interconnect API in order to change memory configuration.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/memory/tegra/Kconfig | 1 +
> drivers/memory/tegra/mc.c | 114 +++++++++++++++++++++++++++++++++++
> drivers/memory/tegra/mc.h | 8 +++
> include/soc/tegra/mc.h | 3 +
> 4 files changed, 126 insertions(+)
>
> diff --git a/drivers/memory/tegra/Kconfig b/drivers/memory/tegra/Kconfig
> index 5bf75b316a2f..7055fdef2c32 100644
> --- a/drivers/memory/tegra/Kconfig
> +++ b/drivers/memory/tegra/Kconfig
> @@ -3,6 +3,7 @@ config TEGRA_MC
> bool "NVIDIA Tegra Memory Controller support"
> default y
> depends on ARCH_TEGRA
> + select INTERCONNECT
> help
> This driver supports the Memory Controller (MC) hardware found on
> NVIDIA Tegra SoCs.
> diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
> index 772aa021b5f6..7ef7ac9e103e 100644
> --- a/drivers/memory/tegra/mc.c
> +++ b/drivers/memory/tegra/mc.c
> @@ -594,6 +594,118 @@ static __maybe_unused irqreturn_t tegra20_mc_irq(int irq, void *data)
> return IRQ_HANDLED;
> }
>
> +static int tegra_mc_icc_set(struct icc_node *src, struct icc_node *dst)
> +{
> + return 0;
> +}
> +
> +static int tegra_mc_icc_aggregate(struct icc_node *node,
> + u32 tag, u32 avg_bw, u32 peak_bw,
> + u32 *agg_avg, u32 *agg_peak)
> +{
> + *agg_avg = min((u64)avg_bw + (*agg_avg), (u64)U32_MAX);
> + *agg_peak = max(*agg_peak, peak_bw);
> +
> + return 0;
> +}
> +
> +/*
> + * Memory Controller (MC) has few Memory Clients that are issuing memory
> + * bandwidth allocation requests to the MC interconnect provider. The MC
> + * provider aggregates the requests and then sends the aggregated request
> + * up to the External Memory Controller (EMC) interconnect provider which
> + * re-configures hardware interface to External Memory (EMEM) in accordance
> + * to the required bandwidth. Each MC interconnect node represents an
> + * individual Memory Client.
> + *
> + * Memory interconnect topology:
> + *
> + * +----+
> + * +--------+ | |
> + * | TEXSRD +--->+ |
> + * +--------+ | |
> + * | | +-----+ +------+
> + * ... | MC +--->+ EMC +--->+ EMEM |
> + * | | +-----+ +------+
> + * +--------+ | |
> + * | DISP.. +--->+ |
> + * +--------+ | |
> + * +----+
> + */
> +static int tegra_mc_interconnect_setup(struct tegra_mc *mc)
> +{
> + struct icc_onecell_data *data;
> + struct icc_node *node;
> + unsigned int num_nodes;
> + unsigned int i;
> + int err;
> +
> + /* older device-trees don't have interconnect properties */
> + if (!of_find_property(mc->dev->of_node, "#interconnect-cells", NULL))
> + return 0;
> +
> + num_nodes = mc->soc->num_clients;
> +
> + data = devm_kzalloc(mc->dev, struct_size(data, nodes, num_nodes),
> + GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + mc->provider.dev = mc->dev;
> + mc->provider.set = tegra_mc_icc_set;

Hmm, maybe the core should not require a set() implementation and we can
just make it optional instead. Then the dummy function would not be needed.

> + mc->provider.data = data;
> + mc->provider.xlate = of_icc_xlate_onecell;
> + mc->provider.aggregate = tegra_mc_icc_aggregate;
> +
> + err = icc_provider_add(&mc->provider);
> + if (err)
> + goto err_msg;

Nit: I am planning to re-organize some of the existing drivers to call
icc_provider_add() after the topology is populated. Could you please move
this after the nodes are created and linked.

> +
> + /* create Memory Controller node */
> + node = icc_node_create(TEGRA_ICC_MC);
> + err = PTR_ERR_OR_ZERO(node);
> + if (err)
> + goto del_provider;
> +
> + node->name = "Memory Controller";
> + icc_node_add(node, &mc->provider);
> +
> + /* link Memory Controller to External Memory Controller */
> + err = icc_link_create(node, TEGRA_ICC_EMC);
> + if (err)
> + goto remove_nodes;
> +
> + for (i = 0; i < num_nodes; i++) {
> + /* create MC client node */
> + node = icc_node_create(mc->soc->clients[i].id);
> + err = PTR_ERR_OR_ZERO(node);
> + if (err)
> + goto remove_nodes;
> +
> + node->name = mc->soc->clients[i].name;
> + icc_node_add(node, &mc->provider);
> +
> + /* link Memory Client to Memory Controller */
> + err = icc_link_create(node, TEGRA_ICC_MC);
> + if (err)
> + goto remove_nodes;
> +
> + data->nodes[i] = node;
> + }
> + data->num_nodes = num_nodes;
> +
> + return 0;
> +
> +remove_nodes:
> + icc_nodes_remove(&mc->provider);
> +del_provider:
> + icc_provider_del(&mc->provider);
> +err_msg:
> + dev_err(mc->dev, "failed to initialize ICC: %d\n", err);
> +
> + return err;
> +}
> +
> static int tegra_mc_probe(struct platform_device *pdev)
> {
> struct resource *res;
> @@ -702,6 +814,8 @@ static int tegra_mc_probe(struct platform_device *pdev)
> }
> }
>
> + tegra_mc_interconnect_setup(mc);
> +
> return 0;
> }
>
> diff --git a/drivers/memory/tegra/mc.h b/drivers/memory/tegra/mc.h
> index afa3ba45c9e6..abeb6a2cc36a 100644
> --- a/drivers/memory/tegra/mc.h
> +++ b/drivers/memory/tegra/mc.h
> @@ -115,4 +115,12 @@ extern const struct tegra_mc_soc tegra132_mc_soc;
> extern const struct tegra_mc_soc tegra210_mc_soc;
> #endif
>
> +/*
> + * These IDs are for internal use of Tegra's ICC, the values are chosen
> + * such that they don't conflict with the device-tree ICC node IDs.
> + */
> +#define TEGRA_ICC_EMC 1000
> +#define TEGRA_ICC_EMEM 2000
> +#define TEGRA_ICC_MC 3000
> +
> #endif /* MEMORY_TEGRA_MC_H */
> diff --git a/include/soc/tegra/mc.h b/include/soc/tegra/mc.h
> index 1238e35653d1..71de023f9f47 100644
> --- a/include/soc/tegra/mc.h
> +++ b/include/soc/tegra/mc.h
> @@ -7,6 +7,7 @@
> #define __SOC_TEGRA_MC_H__
>
> #include <linux/err.h>
> +#include <linux/interconnect-provider.h>
> #include <linux/reset-controller.h>
> #include <linux/types.h>
>
> @@ -178,6 +179,8 @@ struct tegra_mc {
>
> struct reset_controller_dev reset;
>
> + struct icc_provider provider;
> +
> spinlock_t lock;
> };

The rest looks good to me!

Thanks,
Georgi