EMC driver will become mandatory after making it interconnect provider
because interconnect users like display controller driver will fail to
probe using newer device-trees that have interconnect properties. Thus
make driver to probe even if timings or IRQ are missing in device-tree,
the frequency scaling won't be available in this case because there will
be only one frequency available, the frequency that is left from
bootloader.

Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
---
 drivers/memory/tegra/tegra20-emc.c | 61 +++++++++++++++---------------
 1 file changed, 31 insertions(+), 30 deletions(-)

diff --git a/drivers/memory/tegra/tegra20-emc.c 
b/drivers/memory/tegra/tegra20-emc.c
index d2efd0c658c0..28bd9fd4c3c9 100644
--- a/drivers/memory/tegra/tegra20-emc.c
+++ b/drivers/memory/tegra/tegra20-emc.c
@@ -381,6 +381,11 @@ tegra_emc_find_node_by_ram_code(struct device *dev)
        u32 value, ram_code;
        int err;
 
+       if (of_get_child_count(dev->of_node) == 0) {
+               dev_info(dev, "device-tree doesn't have memory timings\n");
+               return NULL;
+       }
+
        if (!of_property_read_bool(dev->of_node, "nvidia,use-ram-code"))
                return of_node_get(dev->of_node);
 
@@ -449,6 +454,9 @@ static long emc_round_rate(unsigned long rate,
        struct tegra_emc *emc = arg;
        unsigned int i;
 
+       if (!emc->num_timings)
+               return clk_get_rate(emc->clk);
+
        min_rate = min(min_rate, emc->timings[emc->num_timings - 1].rate);
 
        for (i = 0; i < emc->num_timings; i++) {
@@ -484,38 +492,21 @@ static int tegra_emc_probe(struct platform_device *pdev)
        struct tegra_emc *emc;
        int irq, err;
 
-       /* driver has nothing to do in a case of memory timing absence */
-       if (of_get_child_count(pdev->dev.of_node) == 0) {
-               dev_info(&pdev->dev,
-                        "EMC device tree node doesn't have memory timings\n");
-               return 0;
-       }
-
-       irq = platform_get_irq(pdev, 0);
-       if (irq < 0) {
-               dev_err(&pdev->dev, "interrupt not specified\n");
-               dev_err(&pdev->dev, "please update your device tree\n");
-               return irq;
-       }
-
-       np = tegra_emc_find_node_by_ram_code(&pdev->dev);
-       if (!np)
-               return -EINVAL;
-
        emc = devm_kzalloc(&pdev->dev, sizeof(*emc), GFP_KERNEL);
-       if (!emc) {
-               of_node_put(np);
+       if (!emc)
                return -ENOMEM;
-       }
 
        init_completion(&emc->clk_handshake_complete);
        emc->clk_nb.notifier_call = tegra_emc_clk_change_notify;
        emc->dev = &pdev->dev;
 
-       err = tegra_emc_load_timings_from_dt(emc, np);
-       of_node_put(np);
-       if (err)
-               return err;
+       np = tegra_emc_find_node_by_ram_code(&pdev->dev);
+       if (np) {
+               err = tegra_emc_load_timings_from_dt(emc, np);
+               of_node_put(np);
+               if (err)
+                       return err;
+       }
 
        emc->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(emc->regs))
@@ -525,11 +516,21 @@ static int tegra_emc_probe(struct platform_device *pdev)
        if (err)
                return err;
 
-       err = devm_request_irq(&pdev->dev, irq, tegra_emc_isr, 0,
-                              dev_name(&pdev->dev), emc);
-       if (err) {
-               dev_err(&pdev->dev, "failed to request IRQ#%u: %d\n", irq, err);
-               return err;
+       irq = platform_get_irq(pdev, 0);
+       if (irq < 0) {
+               dev_err(&pdev->dev, "interrupt not specified\n");
+               dev_err(&pdev->dev, "please update your device tree\n");
+               dev_err(&pdev->dev, "frequency scaling disabled\n");
+
+               emc->num_timings = 0;
+       } else {
+               err = devm_request_irq(&pdev->dev, irq, tegra_emc_isr, 0,
+                                      dev_name(&pdev->dev), emc);
+               if (err) {
+                       dev_err(&pdev->dev, "failed to request IRQ#%u: %d\n",
+                               irq, err);
+                       return err;
+               }
        }
 
        tegra20_clk_set_emc_round_callback(emc_round_rate, emc);
-- 
2.23.0

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