lkml.org 
[lkml]   [2019]   [Jan]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [RFC,5/5] mfd: cros_ec: add EC host command support using rpmsg.
    Hi Peter,

    Missatge de Peter Shih <pihsun@chromium.org> del dia dv., 4 de gen.
    2019 a les 8:58:
    >
    > Thanks for the review.
    > I would leave some formatting comment to v2, and reply others first.
    >
    > On Fri, Jan 4, 2019 at 12:05 AM Enric Balletbo Serra
    > <eballetbo@gmail.com> wrote:
    > >
    > > Hi,
    > >
    > > Many thanks for sending this. Please, add Guenter and me for next
    > > versions, we are interested in it, thanks :)
    > >
    > > Missatge de Pi-Hsun Shih <pihsun@chromium.org> del dia dc., 26 de des.
    > > 2018 a les 8:57:
    > > >
    > > > Add EC host command support through rpmsg.
    > > >
    > > > Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
    > > > ---
    > > > drivers/mfd/cros_ec_dev.c | 9 ++
    > > > drivers/platform/chrome/Kconfig | 8 ++
    > > > drivers/platform/chrome/Makefile | 1 +
    > > > drivers/platform/chrome/cros_ec_rpmsg.c | 164 ++++++++++++++++++++++++
    > > > include/linux/mfd/cros_ec.h | 1 +
    > > > include/linux/mfd/cros_ec_commands.h | 2 +
    > > > 6 files changed, 185 insertions(+)
    > > > create mode 100644 drivers/platform/chrome/cros_ec_rpmsg.c
    > > >
    > > > diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
    > > > index 2d0fee488c5aa8..67983853413d07 100644
    > > > --- a/drivers/mfd/cros_ec_dev.c
    > > > +++ b/drivers/mfd/cros_ec_dev.c
    > > > @@ -414,6 +414,15 @@ static int ec_device_probe(struct platform_device *pdev)
    > > > device_initialize(&ec->class_dev);
    > > > cdev_init(&ec->cdev, &fops);
    > > >
    > > > + if (cros_ec_check_features(ec, EC_FEATURE_SCP)) {
    > > > + dev_info(dev, "SCP detected.\n");
    > > > + /*
    > > > + * Help userspace differentiating ECs from SCP,
    > > > + * regardless of the probing order.
    > > > + */
    > > > + ec_platform->ec_name = CROS_EC_DEV_SCP_NAME;
    > > > + }
    > > > +
    > >
    > > Why userspace should know that this is an SCP? From the userspace
    > > point of view shouldn't be this transparent, we don't do distinctions
    > > when the transport layer is i2c, spi or lpc, and I think that the
    > > cros_ec_rpmsg driver is a cros-ec transport layer, like these. So, I
    > > think that this is not needed.
    > >
    >
    > Since both the EC and the SCP talk in EC host command format here, and they can
    > both exist on the same system, if we don't do the distinction, both of them
    > would be registered as /dev/cros_ec, and cause an error.
    >

    Interesting, so this system will have two cros-ec, one connected via
    spi or i2c to the soc and another one using the M4 within the M8183?

    Actually, on some systems, we have chained EC's (ie cros_ec and
    cros_pd). The way we actually handle the name to access the different
    ECs is create a mfd cell with their specific platform data, I am
    wondering if we can do the same here (see drivers/mfd/cros_ec.c)

    > This change is actually independent to the rpmsg change (EC through all
    > transport layer can report that they have feature EC_FEATURE_SCP, and would
    > then be seen from userspace as /dev/cros_scp), I'll move this to another patch
    > in v2.
    >
    > > > /*
    > > > * Add the class device
    > > > * Link to the character device for creating the /dev entry
    > > > diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
    > > > index 16b1615958aa2d..b03d68eb732177 100644
    > > > --- a/drivers/platform/chrome/Kconfig
    > > > +++ b/drivers/platform/chrome/Kconfig
    > > > @@ -72,6 +72,14 @@ config CROS_EC_SPI
    > > > response time cannot be guaranteed, we support ignoring
    > > > 'pre-amble' bytes before the response actually starts.
    > > >
    > > > +config CROS_EC_RPMSG
    > > > + tristate "ChromeOS Embedded Controller (rpmsg)"
    > > > + depends on MFD_CROS_EC && RPMSG
    > >
    > > I think that this driver is DT-only, && OF ?
    >
    > Would add this in v2.
    >
    > >
    > > > + help
    > > > + If you say Y here, you get support for talking to the ChromeOS EC
    > > > + through rpmsg. This uses a simple byte-level protocol with a
    > > > + checksum.
    > > > +
    > > > config CROS_EC_LPC
    > > > tristate "ChromeOS Embedded Controller (LPC)"
    > > > depends on MFD_CROS_EC && ACPI && (X86 || COMPILE_TEST)
    > > > diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
    > > > index cd591bf872bbe9..3e3190af2b50f4 100644
    > > > --- a/drivers/platform/chrome/Makefile
    > > > +++ b/drivers/platform/chrome/Makefile
    > > > @@ -8,6 +8,7 @@ cros_ec_ctl-objs := cros_ec_sysfs.o cros_ec_lightbar.o \
    > > > obj-$(CONFIG_CROS_EC_CTL) += cros_ec_ctl.o
    > > > obj-$(CONFIG_CROS_EC_I2C) += cros_ec_i2c.o
    > > > obj-$(CONFIG_CROS_EC_SPI) += cros_ec_spi.o
    > > > +obj-$(CONFIG_CROS_EC_RPMSG) += cros_ec_rpmsg.o
    > > > cros_ec_lpcs-objs := cros_ec_lpc.o cros_ec_lpc_reg.o
    > > > cros_ec_lpcs-$(CONFIG_CROS_EC_LPC_MEC) += cros_ec_lpc_mec.o
    > > > obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpcs.o
    > > > diff --git a/drivers/platform/chrome/cros_ec_rpmsg.c b/drivers/platform/chrome/cros_ec_rpmsg.c
    > > > new file mode 100644
    > > > index 00000000000000..f123ca6d1c029c
    > > > --- /dev/null
    > > > +++ b/drivers/platform/chrome/cros_ec_rpmsg.c
    > > > @@ -0,0 +1,164 @@
    > > > +// SPDX-License-Identifier: GPL-2.0
    > > > +//
    > > > +// Copyright 2018 Google LLC.
    > > > +
    > > > +#include <linux/delay.h>
    > > > +#include <linux/kernel.h>
    > > > +#include <linux/module.h>
    > > > +#include <linux/mfd/cros_ec.h>
    > > > +#include <linux/mfd/cros_ec_commands.h>
    > > > +#include <linux/of.h>
    > > > +#include <linux/platform_device.h>
    > > > +#include <linux/rpmsg.h>
    > > > +#include <linux/slab.h>
    > > > +
    > > > +/**
    > > > + * cros_ec_cmd_xfer_rpmsg - Transfer a message over rpmsg and receive the reply
    > > > + *
    > > > + * This is only used for old EC proto version, and is not supported for this
    > > > + * driver.
    > > > + *
    > > > + * @ec_dev: ChromeOS EC device
    > > > + * @ec_msg: Message to transfer
    > > > + */
    > > > +static int cros_ec_cmd_xfer_rpmsg(struct cros_ec_device *ec_dev,
    > > > + struct cros_ec_command *ec_msg)
    > > > +{
    > > > + return -EINVAL;
    > > > +}
    > > > +
    > > > +/**
    > > > + * cros_ec_pkt_xfer_rpmsg - Transfer a packet over rpmsg and receive the reply
    > > > + *
    > > > + * @ec_dev: ChromeOS EC device
    > > > + * @ec_msg: Message to transfer
    > > > + */
    > > > +static int cros_ec_pkt_xfer_rpmsg(struct cros_ec_device *ec_dev,
    > > > + struct cros_ec_command *ec_msg)
    > > > +{
    > > > + struct ec_host_response *response;
    > > > + struct rpmsg_device *rpdev = ec_dev->priv;
    > > > + int len;
    > > > + u8 sum;
    > > > + int ret;
    > > > + int i;
    > > > +
    > > > + ec_msg->result = 0;
    > > > + len = cros_ec_prepare_tx(ec_dev, ec_msg);
    > > > + dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
    > > > +
    > > > + // TODO: This currently relies on that mtk_rpmsg send actually blocks
    > > > + // until ack. Should do the wait here instead.
    > >
    > > Use standard C style comments.
    > >
    > > > + ret = rpmsg_send(rpdev->ept, ec_dev->dout, len);
    > > > +
    > >
    > > Remove that empty line.
    > >
    > > > + if (ret) {
    > > > + dev_err(ec_dev->dev, "rpmsg send failed\n");
    > > > + return ret;
    > > > + }
    > > > +
    > > > + /* check response error code */
    > > > + response = (struct ec_host_response *)ec_dev->din;
    > > > + ec_msg->result = response->result;
    > > > +
    > > > + ret = cros_ec_check_result(ec_dev, ec_msg);
    > > > + if (ret)
    > > > + goto exit;
    > > > +
    > > > + if (response->data_len > ec_msg->insize) {
    > > > + dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
    > > > + response->data_len, ec_msg->insize);
    > > > + ret = -EMSGSIZE;
    > > > + goto exit;
    > > > + }
    > > > +
    > > > + /* copy response packet payload and compute checksum */
    > > > + memcpy(ec_msg->data, ec_dev->din + sizeof(*response),
    > > > + response->data_len);
    > > > +
    > > > + sum = 0;
    > > > + for (i = 0; i < sizeof(*response) + response->data_len; i++)
    > > > + sum += ec_dev->din[i];
    > > > +
    > > > + if (sum) {
    > > > + dev_err(ec_dev->dev, "bad packet checksum, calculated %x\n",
    > > > + sum);
    > > > + ret = -EBADMSG;
    > > > + goto exit;
    > > > + }
    > > > +
    > > > + ret = response->data_len;
    > > > +exit:
    > > > + if (ec_msg->command == EC_CMD_REBOOT_EC)
    > > > + msleep(EC_REBOOT_DELAY_MS);
    > >
    > > Can you explain why this sleep is needed?
    >
    > From the comment of EC_CMD_REBOOT_EC: "The EC is unresponsive for a time after
    > a reboot command. Add a simple delay to make sure that the bus stays locked."
    >
    > This is copied from other transport layer drivers, and probably not needed
    > since we would reload the firmware for SCP while it's rebooting. I would test
    > to see if this is needed when the reboot flow for SCP work as expected.
    > (There's still some firmware work need to be done before it can be tested...)
    >
    > >
    > > > +
    > > > + return ret;
    > > > +}
    > > > +
    > > > +static int cros_ec_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
    > > > + int len, void *priv, u32 src)
    > > > +{
    > > > + struct cros_ec_device *ec_dev = dev_get_drvdata(&rpdev->dev);
    > > > +
    > > > + if (len > ec_dev->din_size) {
    > > > + dev_warn(ec_dev->dev,
    > > > + "ipi received length %d > din_size, truncating", len);
    > > > + len = ec_dev->din_size;
    > > > + }
    > > > +
    > > > + memcpy(ec_dev->din, data, len);
    > > > +
    > > > + return 0;
    > > > +}
    > > > +
    > > > +static int cros_ec_rpmsg_probe(struct rpmsg_device *rpdev)
    > > > +{
    > > > + struct device *dev = &rpdev->dev;
    > > > +
    > > Remove that empty line
    > >
    > > > + struct cros_ec_device *ec_dev;
    > > > + int ret;
    > > > +
    > > > + ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
    > > > + if (!ec_dev)
    > > > + return -ENOMEM;
    > > > +
    > > > + ec_dev->dev = dev;
    > > > + ec_dev->priv = rpdev;
    > > > + ec_dev->cmd_xfer = cros_ec_cmd_xfer_rpmsg;
    > > > + ec_dev->pkt_xfer = cros_ec_pkt_xfer_rpmsg;
    > > > + ec_dev->phys_name = dev_name(&rpdev->dev);
    > > > + ec_dev->din_size = sizeof(struct ec_host_response) +
    > > > + sizeof(struct ec_response_get_protocol_info);
    > > > + ec_dev->dout_size = sizeof(struct ec_host_request);
    > > > + dev_set_drvdata(dev, ec_dev);
    > > > +
    > > > + ret = cros_ec_register(ec_dev);
    > > > + if (ret)
    > >
    > > I'd add an error message here
    > >
    > > dev_err(dev, "cannot register EC\n"
    > >
    > > > + return ret;
    > > > +
    > > > + return 0;
    > > > +}
    > > > +
    > > > +static void cros_ec_rpmsg_remove(struct rpmsg_device *rpdev)
    > >
    > > This function will not be needed after apply [1]. I would recommend
    > > base your patches on top of [2]
    > >
    > > [1] https://lkml.org/lkml/2018/12/12/672
    > > [2] https://lkml.org/lkml/2018/12/12/679
    >
    > Noted.
    >
    > >
    > > > +{
    > > > + struct cros_ec_device *ec_dev = dev_get_drvdata(&rpdev->dev);
    > > > +
    > > > + cros_ec_remove(ec_dev);
    > > > +}
    > > > +
    > >
    > > How this driver is instantiated?
    > >
    > > I expect something like this here (like the other transport layers)
    > >
    > > static const struct of_device_id cros_ec_rpmsg_of_match[] = {
    > > { .compatible = "google,cros-ec-rpmsg", },
    > > { }
    > > };
    > > MODULE_DEVICE_TABLE(of, cros_ec_rpmsg_of_match);
    > >
    > > And the DT containing the compatible = "google,cros-ec-rpmsg" like the
    > > other cros-ec transport layers.
    >
    > This is a part that I'm getting quite confused on how to do properly.
    > For SPI, a spi_device is created for each node listed under spi node in device
    > tree.
    > spi0 {
    > compatible = "xxx-spi";
    > cros_ec@0 {
    > compatible = "google,cros-ec-spi";
    > };
    > }
    >
    > For rpmsg, the rpmsg_device are dynamically created from the request
    > of the SCP, and then a matching rpmsg_driver is used when found.
    > Currently without the cros-ec-rpmsg being in the device tree, the cros_ec_rpmsg
    > module would need to be manually loaded by modprobe.
    >
    > To follow what SPI/I2C does, the device tree would look like:
    > scp {
    > compatible = "mediatek,mt8183-scp";
    > mt8183-rpmsg {
    > compatible = "mediatek,mt8183-rpmsg";
    > cros_ec_rpmsg {
    > compatible = "google,cros-ec-rpmsg";
    > };
    > };
    > };
    > But the rpmsg driver would not actually create those rpmsg_device on probe, but
    > only look at those sub node and load the corresponding rpmsg_driver modules.
    > When requested by SCP to create the rpmsg_device, it would find a matching
    > rpmsg_driver independent on how the device tree looks.
    >
    > So my question is, should these dynamically created rpmsg_device be listed on
    > device tree?
    >

    I think that right now that's our main problem, how to properly
    instantiate all this stuff. One approach that I like is the one used
    in the TI PRU ICSS, they create a pruss_soc_bus driver with the
    purpose to allow the child nodes to be bound. I suspect that something
    similar would work, but I need to look in more detail. See [1]

    [1] https://lkml.org/lkml/2018/11/22/948

    Cheers,
    Enric

    > >
    > > > +static const struct rpmsg_device_id cros_ec_rpmsg_device_id[] = {
    > > > + { .name = "cros-ec-rpmsg", },
    > > > + { /* sentinel */ },
    > >
    > > I got convinced that the '/* sentinel */' comment doesn't means
    > > anything, so use { } only here, remove the comment and the last comma
    > > (there is nothing to separate)
    > > + { }
    > >
    > > > +};
    > > > +
    > > > +static struct rpmsg_driver cros_ec_driver_rpmsg = {
    > > > + .drv.name = KBUILD_MODNAME,
    > >
    > > And something like this here
    > > .drv = {
    > > .name = "cros-ec-rpmsg",
    > > .of_match_table = cros_ec_rpmsg_of_match,
    > > },
    > >
    > > > + .id_table = cros_ec_rpmsg_device_id,
    > > > + .probe = cros_ec_rpmsg_probe,
    > > > + .remove = cros_ec_rpmsg_remove,
    > > > + .callback = cros_ec_rpmsg_callback,
    > > > +};
    > > > +
    > > > +module_rpmsg_driver(cros_ec_driver_rpmsg);
    > > > +
    > > > +MODULE_LICENSE("GPL v2");
    > > > +MODULE_DESCRIPTION("ChromeOS EC multi function device (rpmsg)");
    > > > diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
    > > > index de8b588c8776da..fd297cf8f97295 100644
    > > > --- a/include/linux/mfd/cros_ec.h
    > > > +++ b/include/linux/mfd/cros_ec.h
    > > > @@ -24,6 +24,7 @@
    > > >
    > > > #define CROS_EC_DEV_NAME "cros_ec"
    > > > #define CROS_EC_DEV_PD_NAME "cros_pd"
    > > > +#define CROS_EC_DEV_SCP_NAME "cros_scp"
    > >
    > > I think this definition is not needed.
    > >
    > > >
    > > > /*
    > > > * The EC is unresponsive for a time after a reboot command. Add a
    > > > diff --git a/include/linux/mfd/cros_ec_commands.h b/include/linux/mfd/cros_ec_commands.h
    > > > index fc91082d4c357b..3e5da6e93b2f42 100644
    > > > --- a/include/linux/mfd/cros_ec_commands.h
    > > > +++ b/include/linux/mfd/cros_ec_commands.h
    > > > @@ -856,6 +856,8 @@ enum ec_feature_code {
    > > > EC_FEATURE_RTC = 27,
    > > > /* EC supports CEC commands */
    > > > EC_FEATURE_CEC = 35,
    > > > + /* The MCU exposes a SCP */
    > > > + EC_FEATURE_SCP = 39,
    > >
    > > Same here, I think this is not needed.
    > > > };
    > > >
    > > > #define EC_FEATURE_MASK_0(event_code) (1UL << (event_code % 32))
    > > > --
    > > > 2.20.1.415.g653613c723-goog
    > > >
    > >
    > > Thanks,
    > > Enric

    \
     
     \ /
      Last update: 2019-01-04 12:39    [W:2.306 / U:0.216 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site