Date:   Fri, 10 May 2019 17:32:57 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Brian Norris <briannorris@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] Revert "platform/chrome: cros_ec_spi: Transfer
 messages at high priority"

From: Douglas Anderson <dianders@...omium.org>
Date: Fri, May 10, 2019 at 3:35 PM
To: Mark Brown, Benson Leung, Enric Balletbo i Serra
Cc: <linux-rockchip@...ts.infradead.org>, <drinkcat@...omium.org>,
Guenter Roeck, <briannorris@...omium.org>, <mka@...omium.org>, Douglas
Anderson, <linux-kernel@...r.kernel.org>

> This reverts commit 37a186225a0c020516bafad2727fdcdfc039a1e4.
>
> We have a better solution in the patch ("platform/chrome: cros_ec_spi:
> Set ourselves as timing sensitive").  Let's revert the uglier and less
> reliable solution.
>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Guenter Roeck <groeck@...omium.org>

> ---
>
>  drivers/platform/chrome/cros_ec_spi.c | 80 ++-------------------------
>  1 file changed, 6 insertions(+), 74 deletions(-)
>
> diff --git a/drivers/platform/chrome/cros_ec_spi.c b/drivers/platform/chrome/cros_ec_spi.c
> index 757a115502ec..70ff1ad09012 100644
> --- a/drivers/platform/chrome/cros_ec_spi.c
> +++ b/drivers/platform/chrome/cros_ec_spi.c
> @@ -75,27 +75,6 @@ struct cros_ec_spi {
>         unsigned int end_of_msg_delay;
>  };
>
> -typedef int (*cros_ec_xfer_fn_t) (struct cros_ec_device *ec_dev,
> -                                 struct cros_ec_command *ec_msg);
> -
> -/**
> - * struct cros_ec_xfer_work_params - params for our high priority workers
> - *
> - * @work: The work_struct needed to queue work
> - * @fn: The function to use to transfer
> - * @ec_dev: ChromeOS EC device
> - * @ec_msg: Message to transfer
> - * @ret: The return value of the function
> - */
> -
> -struct cros_ec_xfer_work_params {
> -       struct work_struct work;
> -       cros_ec_xfer_fn_t fn;
> -       struct cros_ec_device *ec_dev;
> -       struct cros_ec_command *ec_msg;
> -       int ret;
> -};
> -
>  static void debug_packet(struct device *dev, const char *name, u8 *ptr,
>                          int len)
>  {
> @@ -371,13 +350,13 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
>  }
>
>  /**
> - * do_cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
> + * cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
>   *
>   * @ec_dev: ChromeOS EC device
>   * @ec_msg: Message to transfer
>   */
> -static int do_cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> -                                  struct cros_ec_command *ec_msg)
> +static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> +                               struct cros_ec_command *ec_msg)
>  {
>         struct ec_host_response *response;
>         struct cros_ec_spi *ec_spi = ec_dev->priv;
> @@ -514,13 +493,13 @@ static int do_cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
>  }
>
>  /**
> - * do_cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
> + * cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
>   *
>   * @ec_dev: ChromeOS EC device
>   * @ec_msg: Message to transfer
>   */
> -static int do_cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
> -                                  struct cros_ec_command *ec_msg)
> +static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
> +                               struct cros_ec_command *ec_msg)
>  {
>         struct cros_ec_spi *ec_spi = ec_dev->priv;
>         struct spi_transfer trans;
> @@ -632,53 +611,6 @@ static int do_cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
>         return ret;
>  }
>
> -static void cros_ec_xfer_high_pri_work(struct work_struct *work)
> -{
> -       struct cros_ec_xfer_work_params *params;
> -
> -       params = container_of(work, struct cros_ec_xfer_work_params, work);
> -       params->ret = params->fn(params->ec_dev, params->ec_msg);
> -}
> -
> -static int cros_ec_xfer_high_pri(struct cros_ec_device *ec_dev,
> -                                struct cros_ec_command *ec_msg,
> -                                cros_ec_xfer_fn_t fn)
> -{
> -       struct cros_ec_xfer_work_params params;
> -
> -       INIT_WORK_ONSTACK(&params.work, cros_ec_xfer_high_pri_work);
> -       params.ec_dev = ec_dev;
> -       params.ec_msg = ec_msg;
> -       params.fn = fn;
> -
> -       /*
> -        * This looks a bit ridiculous.  Why do the work on a
> -        * different thread if we're just going to block waiting for
> -        * the thread to finish?  The key here is that the thread is
> -        * running at high priority but the calling context might not
> -        * be.  We need to be at high priority to avoid getting
> -        * context switched out for too long and the EC giving up on
> -        * the transfer.
> -        */
> -       queue_work(system_highpri_wq, &params.work);
> -       flush_work(&params.work);
> -       destroy_work_on_stack(&params.work);
> -
> -       return params.ret;
> -}
> -
> -static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> -                               struct cros_ec_command *ec_msg)
> -{
> -       return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_pkt_xfer_spi);
> -}
> -
> -static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
> -                               struct cros_ec_command *ec_msg)
> -{
> -       return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_cmd_xfer_spi);
> -}
> -
>  static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
>  {
>         struct device_node *np = dev->of_node;
> --
> 2.21.0.1020.gf2820cf01a-goog
>

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