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SubjectRe: [PATCH v10 3/5] drivers/soc/litex: add LiteX SoC Controller driver
On Wed, Aug 12, 2020 at 02:34:34PM +0200, Mateusz Holenko wrote:
> From: Pawel Czarnecki <pczarnecki@internships.antmicro.com>
>
> This commit adds driver for the FPGA-based LiteX SoC
> Controller from LiteX SoC builder.
>
> Co-developed-by: Mateusz Holenko <mholenko@antmicro.com>
> Signed-off-by: Mateusz Holenko <mholenko@antmicro.com>
> Signed-off-by: Pawel Czarnecki <pczarnecki@internships.antmicro.com>
> ---
...
> +static int litex_check_csr_access(void __iomem *reg_addr)
> +{
> + unsigned long reg;
> +
> + reg = litex_get_reg(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_SIZE);
> +
> + if (reg != SCRATCH_REG_VALUE) {
> + panic("Scratch register read error! Expected: 0x%x but got: 0x%lx",
> + SCRATCH_REG_VALUE, reg);
> + return -EINVAL;
> + }
> +
> + litex_set_reg(reg_addr + SCRATCH_REG_OFF,
> + SCRATCH_REG_SIZE, SCRATCH_TEST_VALUE);
> + reg = litex_get_reg(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_SIZE);
> +
> + if (reg != SCRATCH_TEST_VALUE) {
> + panic("Scratch register write error! Expected: 0x%x but got: 0x%lx",
> + SCRATCH_TEST_VALUE, reg);
> + return -EINVAL;
> + }
> +
> + /* restore original value of the SCRATCH register */
> + litex_set_reg(reg_addr + SCRATCH_REG_OFF,
> + SCRATCH_REG_SIZE, SCRATCH_REG_VALUE);
> +
> + /* Set flag for other drivers */
What does this comment mean?

> + pr_info("LiteX SoC Controller driver initialized");
> +
> + return 0;
> +}
> +
> +struct litex_soc_ctrl_device {
> + void __iomem *base;
> +};
> +
> +static const struct of_device_id litex_soc_ctrl_of_match[] = {
> + {.compatible = "litex,soc-controller"},
> + {},
> +};
> +
> +MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
> +
> +static int litex_soc_ctrl_probe(struct platform_device *pdev)
> +{
> + int result;
> + struct device *dev;
> + struct device_node *node;
> + struct litex_soc_ctrl_device *soc_ctrl_dev;
> +
> + dev = &pdev->dev;
> + node = dev->of_node;
> + if (!node)
> + return -ENODEV;
> +
> + soc_ctrl_dev = devm_kzalloc(dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
> + if (!soc_ctrl_dev)
> + return -ENOMEM;
> +
> + soc_ctrl_dev->base = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(soc_ctrl_dev->base))
> + return PTR_ERR(soc_ctrl_dev->base);
> +
> + result = litex_check_csr_access(soc_ctrl_dev->base);
> + if (result) {
> + // LiteX CSRs access is broken which means that
> + // none of LiteX drivers will most probably
> + // operate correctly
The comment format here with // is not usually used in the kernel, but its not
forbidded. Could you use the /* */ multiline style?

> + BUG();
Instead of stopping the system with BUG, could we just do:

return litex_check_csr_access(soc_ctrl_dev->base);

We already have failure for NODEV/NOMEM so might as well not call BUG() here
too.

> + }
> +
> + return 0;
> +}
> +

Other than that it looks ok to me.

-Stafford

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