Re: [PATCH V3 4/8] memory: tegra: Add Tegra210 EMC clock driver

Dmitry Osipenko
2019-05-14T17:04:08Z

10.05.2019 11:47, Joseph Lo пишет:
> This is the initial patch for Tegra210 EMC clock driver, which doesn't
> include the support code and detail sequence for clock scaling yet.
>
> The driver is designed to support LPDDR4 SDRAM. Because of the LPDDR4
> devices need to do initial time training before it can be used, the
> firmware will help to do that at early boot stage. Then, the trained
> table for the rates we support will pass to the kernel via DT. So the
> driver can get the trained table for clock scaling support.
>
> For the higher rate support (above 800MHz), the periodic training is
> needed for the timing compensation. So basically, two methodologies for
> clock scaling are supported, one is following the clock changing
> sequence to update the EMC table to EMC registers and another is if the
> rate needs periodic training, then we will start a timer to do that
> periodically until it scales to the lower rate.
>
> Based on the work of Peter De Schrijver <pdeschrijver@nvidia.com>.
>
> Signed-off-by: Joseph Lo <josephl@nvidia.com>
> ---

[snip]

> +static int tegra210_emc_probe(struct platform_device *pdev)
> +{
> + int i;
> + unsigned long table_rate;
> + unsigned long current_rate;
> + struct device_node *np;
> + struct platform_device *mc;
> + struct tegra_emc *emc;
> + struct clk_init_data init;
> + struct clk *clk;
> + struct resource *r, res;
> + void *table_addr;
> +
> + emc = devm_kzalloc(&pdev->dev, sizeof(*emc), GFP_KERNEL);
> + if (!emc)
> + return -ENOMEM;
> +
> + np = of_parse_phandle(pdev->dev.of_node, "nvidia,memory-controller", 0);
> + if (!np) {
> + dev_err(&pdev->dev, "could not get memory controller\n");
> + return -ENOENT;
> + }
> +
> + mc = of_find_device_by_node(np);
> + of_node_put(np);
> + if (!mc)
> + return -ENOENT;
> +
> + emc->mc = platform_get_drvdata(mc);
> + if (!emc->mc)
> + return -EPROBE_DEFER;
> +
> + emc->ram_code = tegra_read_ram_code();

emc->ram_code isn't used anywhere in the code.

I haven't checked other fields. Please remove everything that is unused.

> + r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + emc->emc_base[REG_EMC] = devm_ioremap_resource(&pdev->dev, r);
> + r = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> + emc->emc_base[REG_EMC0] = devm_ioremap_resource(&pdev->dev, r);
> + r = platform_get_resource(pdev, IORESOURCE_MEM, 2);
> + emc->emc_base[REG_EMC1] = devm_ioremap_resource(&pdev->dev, r);

Use devm_platform_ioremap_resource().

> + for (i = 0; i < TEGRA_EMC_SRC_COUNT; i++) {
> + emc_src[i] = devm_clk_get(&pdev->dev,
> + emc_src_names[i]);
> + if (IS_ERR(emc_src[i])) {
> + dev_err(&pdev->dev, "Can not find EMC source clock\n");
> + return -ENODATA;
> + }
> + }
> +
> + np = of_parse_phandle(pdev->dev.of_node, "memory-region", 0);
> + if (!np) {
> + dev_err(&pdev->dev, "could not find EMC table\n");
> + goto emc_clk_register;
> + }
> +
> + if (!of_device_is_compatible(np, "nvidia,tegra210-emc-table") ||
> + !of_device_is_available(np)) {
> + dev_err(&pdev->dev, "EMC table is invalid\n");
> + goto emc_clk_register;
> + }
> +
> + of_address_to_resource(np, 0, &res);
> + table_addr = memremap(res.start, resource_size(&res), MEMREMAP_WB);
> + of_node_put(np);
> + if (!table_addr) {
> + dev_err(&pdev->dev, "could not map EMC table\n");
> + goto emc_clk_register;
> + }
> + emc->emc_table = (struct emc_table *)table_addr;
> +
> + for (i = 0; i < TEGRA_EMC_MAX_FREQS; i++)
> + if (emc->emc_table[i].rev != 0)
> + emc->emc_table_size++;
> + else
> + break;
> +
> + /* Init EMC rate statistic data */
> + emc_stats.clkchange_count = 0;
> + spin_lock_init(&emc_stats.spinlock);
> + emc_stats.last_update = get_jiffies_64();
> + emc_stats.last_sel = TEGRA_EMC_MAX_FREQS;
> +
> + /* Check the supported sequence */
> + while (seq->table_rev) {
> + if (seq->table_rev == emc->emc_table[0].rev)
> + break;
> + seq++;
> + }
> + if (!seq->set_clock) {
> + seq = NULL;
> + dev_err(&pdev->dev, "Invalid EMC sequence for table Rev. %d\n",
> + emc->emc_table[0].rev);
> + goto emc_clk_register;

Why do you want to register EMC clock if something fails? KMSG will be
flooded with errors coming from clk_set_rate.

> + }
> +
> + emc_clk_sel = devm_kcalloc(&pdev->dev,
> + emc->emc_table_size,
> + sizeof(struct emc_sel),
> + GFP_KERNEL);
> +
> + /* calculate the rate from source clock */
> + current_rate = emc_get_src_clk_rate() / 1000;
> +
> + /* validate the table */

Please be consistent and start all of the one-line comments with a
lowercase letter.

--
Dmitry