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SubjectRe: [PATCH v1 1/1] platform/mellanox: Add bootctl driver for Mellanox BlueField Soc
On Tue, Jan 29, 2019 at 10:59 PM Liming Sun <lsun@mellanox.com> wrote:
>
> This commit adds the bootctl platform driver for Mellanox BlueField
> Soc, which controls the eMMC boot partition swapping and related
> watchdog configuration.

Thanks for the patch.

My comments below.

First of all, is it a real watchdog with a driver? I think watchdog in
that case should be set up through standard watchdog facilities.

> Reviewed-by: David Woods <dwoods@mellanox.com>

As for Mellanox team I would recommend to take this review as few
basics of kernel programming style and some standard practices.

> Signed-off-by: Liming Sun <lsun@mellanox.com>

> +config MLXBF_BOOTCTL
> + tristate "Mellanox BlueField Firmware Boot Control driver"
> + depends on ARM64

> + default m

Why? What would happen if user chooses n?

> + help
> + The Mellanox BlueField firmware implements functionality to
> + request swapping the primary and alternate eMMC boot
> + partition, and to set up a watchdog that can undo that swap
> + if the system does not boot up correctly. This driver
> + provides sysfs access to the firmware, to be used in
> + conjunction with the eMMC device driver to do any necessary
> + initial swap of the boot partition.

> +struct mlxbf_bootctl_name {
> + int value;
> + const char name[12];

Can't we do simple

const char *name;

?

Why do we need the limitation. Why is it hard coded like this?

> +};
> +
> +static struct mlxbf_bootctl_name boot_names[] = {
> + { MLXBF_BOOTCTL_EXTERNAL, "external" },
> + { MLXBF_BOOTCTL_EMMC, "emmc" },
> + { MLNX_BOOTCTL_SWAP_EMMC, "swap_emmc" },
> + { MLXBF_BOOTCTL_EMMC_LEGACY, "emmc_legacy" },
> + { MLXBF_BOOTCTL_NONE, "none" },

> + { -1, "" }

-1 is usually a bad idea for terminator. It's not in align with many
other structures which require terminator.

> +};

> +
> +static char mlxbf_bootctl_lifecycle_states[][16] = {

static const char * const ... ?

> + [0] = "soft_non_secure",
> + [1] = "secure",
> + [2] = "hard_non_secure",
> + [3] = "rma",
> +};

> +/* Syntactic sugar to avoid having to specify an unused argument. */
> +#define mlxbf_bootctl_smc_call0(smc_op) mlxbf_bootctl_smc_call1(smc_op, 0)
> +
> +static int reset_action_to_val(const char *action, size_t len)
> +{
> + struct mlxbf_bootctl_name *bn;
> +

> + /* Accept string either with or without a newline terminator */
> + if (action[len-1] == '\n')
> + --len;

For a long time we have sysfs_streq() API.

> +
> + for (bn = boot_names; bn->value >= 0; ++bn)
> + if (strncmp(bn->name, action, len) == 0)
> + break;
> +
> + return bn->value;
> +}

> +static ssize_t post_reset_wdog_store(struct device_driver *drv,
> + const char *buf, size_t count)
> +{
> + int err;
> + unsigned long watchdog;
> +
> + err = kstrtoul(buf, 10, &watchdog);
> + if (err)
> + return err;
> +

> + if (mlxbf_bootctl_smc_call1(MLXBF_BOOTCTL_SET_POST_RESET_WDOG,
> + watchdog) < 0)
> + return -EINVAL;

If that call returns an error it shouldn't be shadowed here.

> +
> + return count;
> +}
> +
> +static ssize_t reset_action_show(struct device_driver *drv, char *buf)
> +{

> + return sprintf(buf, "%s\n", reset_action_to_string(
> + mlxbf_bootctl_smc_call0(MLXBF_BOOTCTL_GET_RESET_ACTION)));

Wouldn't be easy to parse this as

int action = ...call0();
return sprintf(...);

?

(int is an arbitrary type here, choose one that suits)

> +}
> +
> +static ssize_t reset_action_store(struct device_driver *drv,
> + const char *buf, size_t count)
> +{
> + int action = reset_action_to_val(buf, count);
> +

> + if (action < 0 || action == MLXBF_BOOTCTL_NONE)
> + return -EINVAL;

Don't shadow an error.

> +
> + if (mlxbf_bootctl_smc_call1(MLXBF_BOOTCTL_SET_RESET_ACTION, action) < 0)
> + return -EINVAL;

Same.

> +
> + return count;
> +}
> +
> +static ssize_t second_reset_action_show(struct device_driver *drv, char *buf)
> +{

> + return sprintf(buf, "%s\n", reset_action_to_string(
> + mlxbf_bootctl_smc_call0(
> + MLXBF_BOOTCTL_GET_SECOND_RESET_ACTION)));

Use temp variable.

> +}
> +
> +static ssize_t second_reset_action_store(struct device_driver *drv,
> + const char *buf, size_t count)
> +{
> + int action = reset_action_to_val(buf, count);
> +
> + if (action < 0)
> + return -EINVAL;

Don't shadow an error.

> +
> + if (mlxbf_bootctl_smc_call1(MLXBF_BOOTCTL_SET_SECOND_RESET_ACTION,
> + action) < 0)
> + return -EINVAL;

Same.

> +
> + return count;
> +}
> +
> +static ssize_t lifecycle_state_show(struct device_driver *drv, char *buf)
> +{

> + int lc_state = mlxbf_bootctl_smc_call1(
> + MLXBF_BOOTCTL_GET_TBB_FUSE_STATUS,
> + MLXBF_BOOTCTL_FUSE_STATUS_LIFECYCLE);

Split it as

int ...;

... = call1();
if (...)

> +
> + if (lc_state < 0)
> + return -EINVAL;

Don't shadow an error.

> +
> + lc_state &= (MLXBF_BOOTCTL_SB_MODE_TEST_MASK |
> + MLXBF_BOOTCTL_SB_MODE_SECURE_MASK);

Better to split like

xxx =
(A | B);

> + /*
> + * If the test bits are set, we specify that the current state may be
> + * due to using the test bits.
> + */

> + if ((lc_state & MLXBF_BOOTCTL_SB_MODE_TEST_MASK) != 0) {

' != 0' is redundant.

> +
> + lc_state &= MLXBF_BOOTCTL_SB_MODE_SECURE_MASK;
> +

> + return sprintf(buf, "%s(test)\n",
> + mlxbf_bootctl_lifecycle_states[lc_state]);

One line?

> + }
> +
> + return sprintf(buf, "%s\n", mlxbf_bootctl_lifecycle_states[lc_state]);
> +}
> +
> +static ssize_t secure_boot_fuse_state_show(struct device_driver *drv, char *buf)
> +{
> + int key;
> + int buf_len = 0;
> + int upper_key_used = 0;
> + int sb_key_state = mlxbf_bootctl_smc_call1(
> + MLXBF_BOOTCTL_GET_TBB_FUSE_STATUS,
> + MLXBF_BOOTCTL_FUSE_STATUS_KEYS);
> +
> + if (sb_key_state < 0)
> + return -EINVAL;
> +

> + for (key = MLXBF_SB_KEY_NUM - 1; key >= 0; key--) {

I'm not sure it's a good idea to put several lines in one sysfs attribute.

> + int burnt = ((sb_key_state & (1 << key)) != 0);

Redundant ' != 0', redundant parens.

> + int valid = ((sb_key_state &
> + (1 << (key + MLXBF_SB_KEY_NUM))) != 0);

Same.

> +
> + buf_len += sprintf(buf + buf_len, "Ver%d:", key);
> + if (upper_key_used) {
> + if (burnt) {
> + if (valid)
> + buf_len += sprintf(buf + buf_len,
> + "Used");

Oh, why not just

const char *status;

if (...) {
...
status = "1";
...
status = "2";
...
}
len = snprintf(buf + len, ..., status);

?

> + else
> + buf_len += sprintf(buf + buf_len,
> + "Wasted");
> + } else {
> + if (valid)
> + buf_len += sprintf(buf + buf_len,
> + "Invalid");
> + else
> + buf_len += sprintf(buf + buf_len,
> + "Skipped");
> + }
> + } else {
> + if (burnt) {
> + if (valid) {
> + upper_key_used = 1;
> + buf_len += sprintf(buf + buf_len,
> + "In use");
> + } else
> + buf_len += sprintf(buf + buf_len,
> + "Burn incomplete");
> + } else {
> + if (valid)
> + buf_len += sprintf(buf + buf_len,
> + "Invalid");
> + else
> + buf_len += sprintf(buf + buf_len,
> + "Free");
> + }
> + }
> + buf_len += sprintf(buf + buf_len, "\n");
> + }
> +
> + return buf_len;
> +}
> +

> +#define MLXBF_BOOTCTL_DRV_ATTR(_name) DRIVER_ATTR_RW(_name)

What the point?

> +static struct attribute_group mlxbf_bootctl_attr_group = {
> + .attrs = mlxbf_bootctl_dev_attrs

+ comma.

> +};

> +static const struct acpi_device_id mlxbf_bootctl_acpi_ids[] = {
> + {"MLNXBF04", 0},

> + {},

No comma for terminator line.

> +};


> +static int mlxbf_bootctl_probe(struct platform_device *pdev)
> +{
> + struct arm_smccc_res res;
> +
> + /*
> + * Ensure we have the UUID we expect for this service.
> + * Note that the functionality we want is present in the first
> + * released version of this service, so we don't check the version.
> + */
> + arm_smccc_smc(MLXBF_BOOTCTL_SIP_SVC_UID, 0, 0, 0, 0, 0, 0, 0, &res);



> + if (res.a0 != 0x89c036b4 || res.a1 != 0x11e6e7d7 ||
> + res.a2 != 0x1a009787 || res.a3 != 0xc4bf00ca)

What is this?!

Can you use UUID API?

> + return -ENODEV;
> +
> + /*
> + * When watchdog is used, it sets boot mode to MLXBF_BOOTCTL_SWAP_EMMC
> + * in case of boot failures. However it doesn't clear the state if there
> + * is no failure. Restore the default boot mode here to avoid any
> + * unnecessary boot partition swapping.
> + */
> + if (mlxbf_bootctl_smc_call1(MLXBF_BOOTCTL_SET_RESET_ACTION,
> + MLXBF_BOOTCTL_EMMC) < 0)

> + pr_err("Unable to reset the EMMC boot mode\n");

Why pr_? Shouldn't be dev_?

> +
> + pr_info("%s (version %s)\n", MLXBF_BOOTCTL_DRIVER_DESCRIPTION,

Ditto.

> + MLXBF_BOOTCTL_DRIVER_VERSION);

No, the driver version is a git SHA sum of the certain tree state.
Remove this definition completely.


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

> +static int mlxbf_bootctl_remove(struct platform_device *pdev)
> +{
> + return 0;
> +}

Waste of lines.

> +/* ARM Standard Service Calls version numbers */
> +#define MLXBF_BOOTCTL_SVC_VERSION_MAJOR 0x0
> +#define MLXBF_BOOTCTL_SVC_VERSION_MINOR 0x2
> +
> +/* Number of svc calls defined. */
> +#define MLXBF_BOOTCTL_NUM_SVC_CALLS 12
> +
> +/* Valid reset actions for MLXBF_BOOTCTL_SET_RESET_ACTION. */

> +#define MLXBF_BOOTCTL_EXTERNAL 0 /* Not boot from eMMC */
> +#define MLXBF_BOOTCTL_EMMC 1 /* From primary eMMC boot partition */
> +#define MLNX_BOOTCTL_SWAP_EMMC 2 /* Swap eMMC boot partitions and reboot */
> +#define MLXBF_BOOTCTL_EMMC_LEGACY 3 /* From primary eMMC in legacy mode */

Since you have this as a sequential starting from 0 you may redefine
boot_names[] as static const char * const and use sysfs_match_string() above.

> +/* Error values (non-zero). */
> +#define MLXBF_BOOTCTL_SMCCC_INVALID_PARAMETERS -2

Is it coming from hardware / firmware ?
Otherwise use standard meaningful kernel error codes.

--
With Best Regards,
Andy Shevchenko

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