Re: [PATCH v1 2/3] mmc: starfive: Add sdio/emmc driver support

[William Qiu <william.qiu@starfivetech.com>]

On 2022/12/9 5:09, Linus Walleij wrote:
> Hi William,
> 
> thanks for your patch!
> 
> On Wed, Dec 7, 2022 at 2:17 PM William Qiu <william.qiu@starfivetech.com> wrote:
> 
>> Add sdio/emmc driver support for StarFive JH7110 soc.
>>
>> Signed-off-by: William Qiu <william.qiu@starfivetech.com>
> 
> (...)
>> +#include <linux/gpio.h>
> 
> Never include this legacy header in new code. Also: you don't use it.
> 
>> +#include <linux/mfd/syscon.h>
>> +#include <linux/mmc/host.h>
>> +#include <linux/module.h>
>> +#include <linux/of_address.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
> 
> You're not using this include either.
> 
>> +#include <linux/regmap.h>
>> +#include <linux/regulator/consumer.h>
> 
> Or this.
> 
>> +#define ALL_INT_CLR            0x1ffff
>> +#define MAX_DELAY_CHAIN                32
>> +
>> +struct starfive_priv {
>> +       struct device *dev;
>> +       struct regmap *reg_syscon;
>> +       u32 syscon_offset;
>> +       u32 syscon_shift;
>> +       u32 syscon_mask;
>> +};
>> +
>> +static unsigned long dw_mci_starfive_caps[] = {
>> +       MMC_CAP_CMD23,
>> +       MMC_CAP_CMD23,
>> +       MMC_CAP_CMD23
>> +};
>> +
>> +static void dw_mci_starfive_set_ios(struct dw_mci *host, struct mmc_ios *ios)
>> +{
>> +       int ret;
>> +       unsigned int clock;
>> +
>> +       if (ios->timing == MMC_TIMING_MMC_DDR52 || ios->timing == MMC_TIMING_UHS_DDR50) {
>> +               clock = (ios->clock > 50000000 && ios->clock <= 52000000) ? 100000000 : ios->clock;
>> +               ret = clk_set_rate(host->ciu_clk, clock);
>> +               if (ret)
>> +                       dev_dbg(host->dev, "Use an external frequency divider %uHz\n", ios->clock);
>> +               host->bus_hz = clk_get_rate(host->ciu_clk);
>> +       } else {
>> +               dev_dbg(host->dev, "Using the internal divider\n");
>> +       }
>> +}
>> +
>> +static int dw_mci_starfive_execute_tuning(struct dw_mci_slot *slot,
>> +                                            u32 opcode)
>> +{
>> +       static const int grade  = MAX_DELAY_CHAIN;
>> +       struct dw_mci *host = slot->host;
>> +       struct starfive_priv *priv = host->priv;
>> +       int raise_point = -1, fall_point = -1;
>> +       int err, prev_err = -1;
> 
> I don't like these default-init to -1. Can you just skip it and assign it
> where it makes most sense instead?
> 
>> +       int found = 0;
> 
> This looks like a bool.
> 
>> +       int i;
>> +       u32 regval;
>> +
>> +       for (i = 0; i < grade; i++) {
>> +               regval = i << priv->syscon_shift;
>> +               err = regmap_update_bits(priv->reg_syscon, priv->syscon_offset,
>> +                                               priv->syscon_mask, regval);
>> +               if (err)
>> +                       return err;
>> +               mci_writel(host, RINTSTS, ALL_INT_CLR);
>> +
>> +               err = mmc_send_tuning(slot->mmc, opcode, NULL);
>> +               if (!err)
>> +                       found = 1;
>> +
>> +               if (i > 0) {
>> +                       if (err && !prev_err)
>> +                               fall_point = i - 1;
>> +                       if (!err && prev_err)
>> +                               raise_point = i;
>> +               }
>> +
>> +               if (raise_point != -1 && fall_point != -1)
>> +                       goto tuning_out;
> 
> There are just these raise point (shouldn't this be "rise_point" in proper
> english?) and fall point, this misses some comments explaining what is
> going on, the code is not intuitively eviden. Rise and fall of *what* for
> example.
> 
>> +
>> +               prev_err = err;
>> +               err = 0;
>> +       }
>> +
>> +tuning_out:
>> +       if (found) {
>> +               if (raise_point == -1)
>> +                       raise_point = 0;
>> +               if (fall_point == -1)
>> +                       fall_point = grade - 1;
>> +               if (fall_point < raise_point) {
>> +                       if ((raise_point + fall_point) >
>> +                           (grade - 1))
>> +                               i = fall_point / 2;
>> +                       else
>> +                               i = (raise_point + grade - 1) / 2;
>> +               } else {
>> +                       i = (raise_point + fall_point) / 2;
>> +               }
> 
> Likewise here, explain what grade is, refer to the eMMC spec if necessary.
> 
> (...)
>> +       ret = of_parse_phandle_with_fixed_args(host->dev->of_node,
>> +                                               "starfive,sys-syscon", 3, 0, &args);
>> +       if (ret) {
>> +               dev_err(host->dev, "Failed to parse starfive,sys-syscon\n");
>> +               return -EINVAL;
>> +       }
>> +
>> +       priv->reg_syscon = syscon_node_to_regmap(args.np);
>> +       of_node_put(args.np);
>> +       if (IS_ERR(priv->reg_syscon))
>> +               return PTR_ERR(priv->reg_syscon);
>> +
>> +       priv->syscon_offset = args.args[0];
>> +       priv->syscon_shift  = args.args[1];
>> +       priv->syscon_mask   = args.args[2];
> 
> Why should these three things be in the device tree instead of being derived
> from the compatible-string or just plain hard-coded as #defines?
> I don't get it.
> 
Hi Linus,

I'm sorry to bother you, but as for the definition of syscon, after discussing with 
my colleagues, we think it is easier to distinguish SDIO0 and SDIO1 by defining it in
the device tree, and the code compatibility is better.

Best Regards
William Qiu
>> +static int dw_mci_starfive_probe(struct platform_device *pdev)
>> +{
>> +       return dw_mci_pltfm_register(pdev, &starfive_data);
>> +}
>> +
>> +static int dw_mci_starfive_remove(struct platform_device *pdev)
>> +{
>> +       return dw_mci_pltfm_remove(pdev);
>> +}
> 
> Can't you just assign dw_mci_pltfm_remove() to .remove?
> 
> Other than these things, the driver looks good!
> 
> Yours,
> Linus Walleij