Hi Jarko, Andriy,
Could you please take a look?
Best Regards,
Jan
pon., 25 lip 2022 o 10:03 Jan Dabros <jsd@xxxxxxxxxxxx> napisał(a):
>
> In order to optimize performance, limit amount of back and forth
> transactions between x86 and PSP. This is done by introduction of
> cooldown period - that is window in which x86 isn't releasing the bus
> immediately after each I2C transaction.
>
> In order to protect PSP from being starved while waiting for
> arbitration, after a programmed time bus is automatically released by a
> deferred function.
>
> Signed-off-by: Jan Dabros <jsd@xxxxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-designware-amdpsp.c | 68 +++++++++++++++++-----
> 1 file changed, 53 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-amdpsp.c b/drivers/i2c/busses/i2c-designware-amdpsp.c
> index b624356c945f..2e1bb5ae72c3 100644
> --- a/drivers/i2c/busses/i2c-designware-amdpsp.c
> +++ b/drivers/i2c/busses/i2c-designware-amdpsp.c
> @@ -6,6 +6,7 @@
> #include <linux/io-64-nonatomic-lo-hi.h>
> #include <linux/psp-sev.h>
> #include <linux/types.h>
> +#include <linux/workqueue.h>
>
> #include <asm/msr.h>
>
> @@ -15,6 +16,8 @@
> #define PSP_MBOX_OFFSET 0x10570
> #define PSP_CMD_TIMEOUT_US (500 * USEC_PER_MSEC)
>
> +#define PSP_I2C_COOLDOWN_TIME_MS 100
> +
> #define PSP_I2C_REQ_BUS_CMD 0x64
> #define PSP_I2C_REQ_RETRY_CNT 400
> #define PSP_I2C_REQ_RETRY_DELAY_US (25 * USEC_PER_MSEC)
> @@ -240,6 +243,42 @@ static int psp_send_i2c_req(enum psp_i2c_req_type i2c_req_type)
> return ret;
> }
>
> +static void release_bus_now(void)
> +{
> + int status;
> +
> + if (!psp_i2c_sem_acquired)
> + return;
> +
> + status = psp_send_i2c_req(PSP_I2C_REQ_RELEASE);
> + if (status)
> + return;
> +
> + dev_dbg(psp_i2c_dev, "PSP semaphore held for %ums\n",
> + jiffies_to_msecs(jiffies - psp_i2c_sem_acquired));
> +
> + psp_i2c_sem_acquired = 0;
> +}
> +
> +static void psp_release_i2c_bus_deferred(struct work_struct *work)
> +{
> +
> + mutex_lock(&psp_i2c_access_mutex);
> +
> + /*
> + * If there is any pending transaction, cannot release the bus here.
> + * psp_release_i2c_bus will take care of this later.
> + */
> + if (psp_i2c_access_count)
> + goto cleanup;
> +
> + release_bus_now();
> +
> +cleanup:
> + mutex_unlock(&psp_i2c_access_mutex);
> +}
> +static DECLARE_DELAYED_WORK(release_queue, psp_release_i2c_bus_deferred);
> +
> static int psp_acquire_i2c_bus(void)
> {
> int status;
> @@ -250,21 +289,23 @@ static int psp_acquire_i2c_bus(void)
> if (psp_i2c_mbox_fail)
> goto cleanup;
>
> + psp_i2c_access_count++;
> +
> /*
> - * Simply increment usage counter and return if PSP semaphore was
> - * already taken by kernel.
> + * No need to request bus arbitration once we are inside cooldown
> + * period.
> */
> - if (psp_i2c_access_count) {
> - psp_i2c_access_count++;
> + if (psp_i2c_sem_acquired)
> goto cleanup;
> - }
>
> status = psp_send_i2c_req(PSP_I2C_REQ_ACQUIRE);
> if (status)
> goto cleanup;
>
> psp_i2c_sem_acquired = jiffies;
> - psp_i2c_access_count++;
> +
> + schedule_delayed_work(&release_queue,
> + msecs_to_jiffies(PSP_I2C_COOLDOWN_TIME_MS));
>
> /*
> * In case of errors with PSP arbitrator psp_i2c_mbox_fail variable is
> @@ -279,8 +320,6 @@ static int psp_acquire_i2c_bus(void)
>
> static void psp_release_i2c_bus(void)
> {
> - int status;
> -
> mutex_lock(&psp_i2c_access_mutex);
>
> /* Return early if mailbox was malfunctional */
> @@ -295,13 +334,12 @@ static void psp_release_i2c_bus(void)
> if (psp_i2c_access_count)
> goto cleanup;
>
> - /* Send a release command to PSP */
> - status = psp_send_i2c_req(PSP_I2C_REQ_RELEASE);
> - if (status)
> - goto cleanup;
> -
> - dev_dbg(psp_i2c_dev, "PSP semaphore held for %ums\n",
> - jiffies_to_msecs(jiffies - psp_i2c_sem_acquired));
> + /*
> + * Send a release command to PSP if the cooldown timeout elapsed but x86 still
> + * owns the ctrlr.
> + */
> + if (!delayed_work_pending(&release_queue))
> + release_bus_now();
>
> cleanup:
> mutex_unlock(&psp_i2c_access_mutex);
> --
> 2.37.1.359.gd136c6c3e2-goog
>
