2016-07-25 13:14 GMT+02:00 Thierry Reding [off-list ref]:

On Tue, Jul 19, 2016 at 03:36:37PM +0200, Mirza Krak wrote:

quoted

+config TEGRA_NOR
+     tristate "Nvidia Tegra NOR flash bus driver a.k.a GMI/SNOR"
+             depends on ARCH_TEGRA_2x_SOC || ARCH_TEGRA_3x_SOC

I think an ARCH_TEGRA dependency is enough here.

ACK.

quoted

+             depends on OF

You can drop this because Tegra has been OF-only for a long time now.

ACK.

quoted

+             help
+                     Driver for NOR flash bus found on Tegra30/20 SOC`s.

Maybe make this "Driver for GMI controller found on NVIDIA Tegra SoCs."
or similar in light of the name change.

ACK.

quoted

--- /dev/null
+++ b/drivers/bus/tegra-nor.c

@@ -0,0 +1,118 @@
+/*
+ * Driver for Nvidia NOR Flash bus a.k.a SNOR/GMI.

Nit: I encourage the use of "NVIDIA" as spelling for consistency.

ACK.

quoted

+static int __init nor_parse_dt(struct platform_device *pdev,
+                             void __iomem *base)
+{
+     struct device_node *of_node = pdev->dev.of_node;
+     u32 config, timing[TEGRA_NOR_TIMING_REG_COUNT];
+     int ret;
+
+     ret = of_property_read_u32_array(of_node, "nvidia,cs-timing",
+                                      timing, TEGRA_NOR_TIMING_REG_COUNT);
+     if (!ret) {
+             writel(timing[0], base + TEGRA_NOR_TIMING0);
+             writel(timing[1], base + TEGRA_NOR_TIMING1);
+     }
+
+     ret = of_property_read_u32(of_node, "nvidia,config", &config);
+     if (ret)
+             return ret;
+
+     config |= TEGRA_NOR_CONFIG_GO;
+     writel(config, base + TEGRA_NOR_CONFIG);

My preference would be for the tegra_gmi_parse_dt() function not to do
any register programming. Instead I think it would be better to store
any of the parameters inside a struct tegra_gmi and do the programming
from within tegra_gmi_probe() (or via an other function such as
tegra_gmi_initialize(), called from tegra_gmi_probe()).

The reason is that you'll most likely want to do this programming when
you resume from suspend, and you could reuse tegra_gmi_initialize() to
do that.

ACK.

quoted

+
+     if (of_get_child_count(of_node))
+             ret = of_platform_populate(of_node,
+                                of_default_bus_match_table,
+                                NULL, &pdev->dev);

Why the extra check? of_platform_populate() is almost a no-op if there
aren't any children anyway. What it will do is set the OF_POPULATED_BUS
flag, but I think we want that irrespective of whether or not there are
any children.

Was there any problem with calling it unconditionally that made you opt
for the extra check?

I have not tested calling it unconditionally. Used another driver as
reference and they had that condition (drivers/bus/imx-weim.c), that
driver does not mention why the condition is there. But will test
removing the condition and see what happens.

Also, I think you can call of_platform_default_populate(), which is a
little shorter than the above because you can omit the match table.

Will look in to this.

quoted

+
+     return ret;
+}
+
+static int __init nor_probe(struct platform_device *pdev)
+{
+     struct resource *res;
+     struct clk *clk;
+     void __iomem *base;
+     int ret;
+
+     /* get the resource */
+     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+     base = devm_ioremap_resource(&pdev->dev, res);
+     if (IS_ERR(base))
+             return PTR_ERR(base);
+
+     /* get the clock */
+     clk = devm_clk_get(&pdev->dev, NULL);

Let's use a consumer name here. The problem with a NULL consumer name is
that it effectively restricts the DT binding. It means that whatever the
clock is its name needs to be the first in a clock-names property. We'll
likely get away with this because there's only one clock, but should we
ever need to add another we'd need to add wording to the device tree
bindings that the "gmi" entry needs to be first.

I'm not sure if that's clear, so I'll try to explain in other words: If
you pass a NULL consumer name to clk_get() it will simply use the first
clock in the clocks property. If you want to later extend the DT binding
by adding a clock in a backwards-compatible way, you'll need to add the
restriction that the "gmi" clock (the one that was previously unnamed)
must be the first in the clock-names and clocks properties.

That's all a little confusing, so let's avoid this by giving it a proper
consumer name to begin with.

Got it. Will add a proper consumer name.

quoted

+     if (IS_ERR(clk))
+             return PTR_ERR(clk);
+
+     ret = clk_prepare_enable(clk);
+     if (ret)
+             return ret;
+
+     /* parse the device node */
+     ret = nor_parse_dt(pdev, base);
+     if (ret) {
+             dev_err(&pdev->dev, "%s fail to create devices.\n",
+                     pdev->dev.of_node->full_name);
+             clk_disable_unprepare(clk);
+             return ret;
+     }

The good thing if you don't do any programming in tegra_gmi_parse_dt(),
is that you can easily move the clk_prepare_enable() call to here where
things can't fail anymore, so you don't have to add cleanup code.

ACK.

quoted

+
+     dev_info(&pdev->dev, "Driver registered.\n");

Please avoid this kind of output. Users expect that everything will work
so you want to let them know when something goes wrong, and be quiet
when all goes as expected.

Will remove that.

quoted

+static struct platform_driver nor_driver = {
+     .driver = {
+             .name           = "tegra-nor",
+             .of_match_table = nor_id_table,
+     },
+};
+module_platform_driver_probe(nor_driver, nor_probe);
+
+MODULE_AUTHOR("Mirza Krak <mirza.krak@gmail.com");
+MODULE_DESCRIPTION("NVIDIA Tegra NOR Bus Driver");
+MODULE_LICENSE("GPL");

You're header comment says GPL version 2, which means that the
MODULE_LICENSE needs to be "GPL v2". "GPL" means "version 2 or later".

Ok, I do not really mind it being GPL version 2 or later so will
change the header comment instead if that is ok.


Best regards,
Mirza