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Date: Fri, 14 Jun 2019 10:23:57 -0600
From: Nick Crews <ncrews@...omium.org>
To: Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Collabora Kernel ML <kernel@...labora.com>,
Guenter Roeck <groeck@...omium.org>,
Benson Leung <bleung@...omium.org>,
Dmitry Torokhov <dtor@...omium.org>,
Ezequiel Garcia <ezequiel@...labora.com>,
Arnd Bergmann <arnd@...db.de>,
Thomas Gleixner <tglx@...utronix.de>,
Duncan Laurie <dlaurie@...gle.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v4] platform/chrome: cros_ec_lpc: Choose Microchip EC at runtime
On Thu, Jun 13, 2019 at 10:34 PM Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> On many boards, communication between the kernel and the Embedded
> Controller happens over an LPC bus. In these cases, the kernel config
> CONFIG_CROS_EC_LPC is enabled. Some of these LPC boards contain a
> Microchip Embedded Controller (MEC) that is different from the regular
> EC. On these devices, the same LPC bus is used, but the protocol is
> a little different. In these cases, the CONFIG_CROS_EC_LPC_MEC kernel
> config is enabled. Currently, the kernel decides at compile-time whether
> or not to use the MEC variant, and, when that kernel option is selected
> it breaks the other boards. We would like a kind of runtime detection to
> avoid this.
>
> This patch adds that detection mechanism by probing the protocol at
> runtime, first we assume that a MEC variant is connected, and if the
> protocol fails it fallbacks to the regular EC. This adds a bit of
> overload because we try to read twice on those LPC boards that doesn't
> contain a MEC variant, but is a better solution than having to select the
> EC variant at compile-time.
>
> While here also fix the alignment in Kconfig file for this config option
> replacing the spaces by tabs.
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> Reviewed-by: Ezequiel Garcia <ezequiel@...labora.com>
> Tested-by: Nick Crews <ncrews@...omium.org>
> ---
> Hi,
>
> This is another attempt to solve the issue to be able to select at
> runtime the CrOS MEC variant. My first thought was check for a device
> ID, the MEC1322 has a register that contains the device ID, however I
> am not sure if we can read that register from the host without
> modifying the firmware. Also, I am not sure if the MEC1322 is the only
> device used that supports that LPC protocol variant, so I ended with a
> more easy solution, check if the protocol fails or not. Some background
> on this issue can be found [1] and [2]
>
> The patch has been tested on:
> - Acer Chromebook R11 (Cyan - MEC variant)
> - Pixel Chromebook 2015 (Samus - non-MEC variant)
> - Dell Chromebook 11 (Wolf - non-MEC variant)
> - Toshiba Chromebook (Leon - non-MEC variant)
>
> Best regards,
> Enric
>
> [1] https://bugs.chromium.org/p/chromium/issues/detail?id=932626
> [2] https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/1474254
>
> Changes in v4:
> - Change the logic to test the protocols as suggested by Nick Crews.
> - Add the proper cros_ec_lpc_mec.h include. (Nick Crews)
> - Fix some const and missing casts. (Nick Crews)
> - Clean up related doc-strings. (Nick Crews)
>
> Changes in v3:
> - Kconfig: Split across multiple lines to keep it under 80 characters.
> - Improve kernel-doc as suggested by Nick Crews.
> - Convert msg in write function to const.
> - Add rb and tb tags.
>
> Changes in v2:
> - Remove global bool to indicate the kind of variant as suggested by Ezequiel.
> - Create an internal operations struct to allow different variants.
>
> drivers/platform/chrome/Kconfig | 29 +++------
> drivers/platform/chrome/Makefile | 2 +-
> drivers/platform/chrome/cros_ec_lpc.c | 78 ++++++++++++++++-------
> drivers/platform/chrome/cros_ec_lpc_mec.h | 14 ++++
> drivers/platform/chrome/cros_ec_lpc_reg.c | 41 ++++--------
> drivers/platform/chrome/cros_ec_lpc_reg.h | 23 +++----
> drivers/platform/chrome/wilco_ec/Kconfig | 2 +-
> 7 files changed, 98 insertions(+), 91 deletions(-)
>
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index 2826f7136f65..453e69733842 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -83,28 +83,17 @@ config CROS_EC_SPI
> 'pre-amble' bytes before the response actually starts.
>
> config CROS_EC_LPC
> - tristate "ChromeOS Embedded Controller (LPC)"
> - depends on MFD_CROS_EC && ACPI && (X86 || COMPILE_TEST)
> - help
> - If you say Y here, you get support for talking to the ChromeOS EC
> - over an LPC bus. This uses a simple byte-level protocol with a
> - checksum. This is used for userspace access only. The kernel
> - typically has its own communication methods.
> -
> - To compile this driver as a module, choose M here: the
> - module will be called cros_ec_lpc.
> -
> -config CROS_EC_LPC_MEC
> - bool "ChromeOS Embedded Controller LPC Microchip EC (MEC) variant"
> - depends on CROS_EC_LPC
> - default n
> + tristate "ChromeOS Embedded Controller (LPC)"
> + depends on MFD_CROS_EC && ACPI && (X86 || COMPILE_TEST)
> help
> - If you say Y here, a variant LPC protocol for the Microchip EC
> - will be used. Note that this variant is not backward compatible
> - with non-Microchip ECs.
> + If you say Y here, you get support for talking to the ChromeOS EC
> + over an LPC bus, including the LPC Microchip EC (MEC) variant.
> + This uses a simple byte-level protocol with a checksum. This is
> + used for userspace access only. The kernel typically has its own
> + communication methods.
>
> - If you have a ChromeOS Embedded Controller Microchip EC variant
> - choose Y here.
> + To compile this driver as a module, choose M here: the
> + module will be called cros_ec_lpcs.
>
> config CROS_EC_PROTO
> bool
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index 1b2f1dcfcd5c..da9aa08d9fa6 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -10,7 +10,7 @@ obj-$(CONFIG_CROS_EC_I2C) += cros_ec_i2c.o
> obj-$(CONFIG_CROS_EC_RPMSG) += cros_ec_rpmsg.o
> obj-$(CONFIG_CROS_EC_SPI) += cros_ec_spi.o
> cros_ec_lpcs-objs := cros_ec_lpc.o cros_ec_lpc_reg.o
> -cros_ec_lpcs-$(CONFIG_CROS_EC_LPC_MEC) += cros_ec_lpc_mec.o
> +cros_ec_lpcs-objs += cros_ec_lpc_mec.o
> obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpcs.o
> obj-$(CONFIG_CROS_EC_PROTO) += cros_ec_proto.o cros_ec_trace.o
> obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT) += cros_kbd_led_backlight.o
> diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
> index c9c240fbe7c6..d6ba6b464abc 100644
> --- a/drivers/platform/chrome/cros_ec_lpc.c
> +++ b/drivers/platform/chrome/cros_ec_lpc.c
> @@ -23,11 +23,29 @@
> #include <linux/printk.h>
> #include <linux/suspend.h>
>
> +#include "cros_ec_lpc_mec.h"
Good catch, but this isn't everything. See below.
> #include "cros_ec_lpc_reg.h"
>
> #define DRV_NAME "cros_ec_lpcs"
> #define ACPI_DRV_NAME "GOOG0004"
>
> +/**
> + * struct lpc_driver_ops - LPC driver operations
> + * @read: Copy length bytes from EC address offset into buffer dest. Returns
> + * the 8-bit checksum of all bytes read.
> + * @write: Copy length bytes from buffer msg into EC address offset. Returns
> + * the 8-bit checksum of all bytes written.
> + */
> +struct lpc_driver_ops {
> + u8 (*read)(unsigned int offset, unsigned int length, u8 *dest);
> + u8 (*write)(unsigned int offset, unsigned int length, const u8 *msg);
> +};
> +
> +static struct lpc_driver_ops cros_ec_lpc_ops = {
> + .read = cros_ec_lpc_mec_read_bytes,
> + .write = cros_ec_lpc_mec_write_bytes,
> +};
As I mentioned to you directly, maybe don't define these statically here,
but assign the methods in cros_ec_lpc_probe(), so down there
you can see explicitly what the defaults are?
> +
> /* True if ACPI device is present */
> static bool cros_ec_lpc_acpi_device_found;
>
> @@ -38,7 +56,7 @@ static int ec_response_timed_out(void)
>
> usleep_range(200, 300);
> do {
> - if (!(cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_CMD, 1, &data) &
> + if (!(cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_CMD, 1, &data) &
> EC_LPC_STATUS_BUSY_MASK))
> return 0;
> usleep_range(100, 200);
> @@ -58,11 +76,11 @@ static int cros_ec_pkt_xfer_lpc(struct cros_ec_device *ec,
> ret = cros_ec_prepare_tx(ec, msg);
>
> /* Write buffer */
> - cros_ec_lpc_write_bytes(EC_LPC_ADDR_HOST_PACKET, ret, ec->dout);
> + cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_PACKET, ret, ec->dout);
>
> /* Here we go */
> sum = EC_COMMAND_PROTOCOL_3;
> - cros_ec_lpc_write_bytes(EC_LPC_ADDR_HOST_CMD, 1, &sum);
> + cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_CMD, 1, &sum);
>
> if (ec_response_timed_out()) {
> dev_warn(ec->dev, "EC responsed timed out\n");
> @@ -71,15 +89,15 @@ static int cros_ec_pkt_xfer_lpc(struct cros_ec_device *ec,
> }
>
> /* Check result */
> - msg->result = cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> + msg->result = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> ret = cros_ec_check_result(ec, msg);
> if (ret)
> goto done;
>
> /* Read back response */
> dout = (u8 *)&response;
> - sum = cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_PACKET, sizeof(response),
> - dout);
> + sum = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PACKET, sizeof(response),
> + dout);
>
> msg->result = response.result;
>
> @@ -92,9 +110,9 @@ static int cros_ec_pkt_xfer_lpc(struct cros_ec_device *ec,
> }
>
> /* Read response and process checksum */
> - sum += cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_PACKET +
> - sizeof(response), response.data_len,
> - msg->data);
> + sum += cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PACKET +
> + sizeof(response), response.data_len,
> + msg->data);
>
> if (sum) {
> dev_err(ec->dev,
> @@ -134,17 +152,17 @@ static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
> sum = msg->command + args.flags + args.command_version + args.data_size;
>
> /* Copy data and update checksum */
> - sum += cros_ec_lpc_write_bytes(EC_LPC_ADDR_HOST_PARAM, msg->outsize,
> - msg->data);
> + sum += cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_PARAM, msg->outsize,
> + msg->data);
>
> /* Finalize checksum and write args */
> args.checksum = sum;
> - cros_ec_lpc_write_bytes(EC_LPC_ADDR_HOST_ARGS, sizeof(args),
> - (u8 *)&args);
> + cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_ARGS, sizeof(args),
> + (u8 *)&args);
>
> /* Here we go */
> sum = msg->command;
> - cros_ec_lpc_write_bytes(EC_LPC_ADDR_HOST_CMD, 1, &sum);
> + cros_ec_lpc_ops.write(EC_LPC_ADDR_HOST_CMD, 1, &sum);
>
> if (ec_response_timed_out()) {
> dev_warn(ec->dev, "EC responsed timed out\n");
> @@ -153,14 +171,13 @@ static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
> }
>
> /* Check result */
> - msg->result = cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> + msg->result = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_DATA, 1, &sum);
> ret = cros_ec_check_result(ec, msg);
> if (ret)
> goto done;
>
> /* Read back args */
> - cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_ARGS, sizeof(args),
> - (u8 *)&args);
> + cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_ARGS, sizeof(args), (u8 *)&args);
>
> if (args.data_size > msg->insize) {
> dev_err(ec->dev,
> @@ -174,8 +191,8 @@ static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
> sum = msg->command + args.flags + args.command_version + args.data_size;
>
> /* Read response and update checksum */
> - sum += cros_ec_lpc_read_bytes(EC_LPC_ADDR_HOST_PARAM, args.data_size,
> - msg->data);
> + sum += cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PARAM, args.data_size,
> + msg->data);
>
> /* Verify checksum */
> if (args.checksum != sum) {
> @@ -205,13 +222,13 @@ static int cros_ec_lpc_readmem(struct cros_ec_device *ec, unsigned int offset,
>
> /* fixed length */
> if (bytes) {
> - cros_ec_lpc_read_bytes(EC_LPC_ADDR_MEMMAP + offset, bytes, s);
> + cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + offset, bytes, s);
> return bytes;
> }
>
> /* string */
> for (; i < EC_MEMMAP_SIZE; i++, s++) {
> - cros_ec_lpc_read_bytes(EC_LPC_ADDR_MEMMAP + i, 1, s);
> + cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + i, 1, s);
> cnt++;
> if (!*s)
> break;
> @@ -248,10 +265,23 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
> return -EBUSY;
> }
>
> - cros_ec_lpc_read_bytes(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
> + /*
> + * Read the mapped ID twice, the first one is assuming the
> + * EC is a Microchip Embedded Controller (MEC) variant, if the
> + * protocol fails, fallback to the non MEC variant and try to
> + * read again the ID.
> + */
As metioned above, maybe assign cros_ec_lpc_mec_read_bytes and
cros_ec_lpc_mec_write_bytes here, so it's clear what the defaults are,
instead of assigning them statically above.
> + cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
> if (buf[0] != 'E' || buf[1] != 'C') {
> - dev_err(dev, "EC ID not detected\n");
> - return -ENODEV;
> + /* Re-assign read/write operations for the non MEC variant */
> + cros_ec_lpc_ops.read = cros_ec_lpc_read_bytes;
> + cros_ec_lpc_ops.write = cros_ec_lpc_write_bytes;
> + cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2,
> + buf);
> + if (buf[0] != 'E' || buf[1] != 'C') {
> + dev_err(dev, "EC ID not detected\n");
> + return -ENODEV;
> + }
> }
>
> if (!devm_request_region(dev, EC_HOST_CMD_REGION0,
> diff --git a/drivers/platform/chrome/cros_ec_lpc_mec.h b/drivers/platform/chrome/cros_ec_lpc_mec.h
> index aa1018f6b0f2..fcaabdbb5e62 100644
> --- a/drivers/platform/chrome/cros_ec_lpc_mec.h
> +++ b/drivers/platform/chrome/cros_ec_lpc_mec.h
> @@ -76,4 +76,18 @@ int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length);
> u8 cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
> unsigned int offset, unsigned int length, u8 *buf);
>
> +/*
> + * An instance of the read function of struct lpc_driver_ops, used for the
> + * MEC variant of LPC EC.
> + */
> +u8 cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
> + u8 *dest);
> +
> +/*
> + * An instance of the write function of struct lpc_driver_ops, used for the
> + * MEC variant of LPC EC.
> + */
> +u8 cros_ec_lpc_mec_write_bytes(unsigned int offset, unsigned int length,
> + const u8 *msg);
> +
> #endif /* __CROS_EC_LPC_MEC_H */
> diff --git a/drivers/platform/chrome/cros_ec_lpc_reg.c b/drivers/platform/chrome/cros_ec_lpc_reg.c
> index 0f5cd0ac8b49..3bfeb5ad59ba 100644
> --- a/drivers/platform/chrome/cros_ec_lpc_reg.c
> +++ b/drivers/platform/chrome/cros_ec_lpc_reg.c
> @@ -9,7 +9,7 @@
>
> #include "cros_ec_lpc_mec.h"
Good call above, but you should include cros_ec_lpc_reg.h here as well.
>
> -static u8 lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
> +u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
> {
> int i;
> int sum = 0;
> @@ -23,7 +23,8 @@ static u8 lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
> return sum;
> }
>
> -static u8 lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
> +u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length,
> + const u8 *msg)
> {
> int i;
> int sum = 0;
> @@ -37,9 +38,9 @@ static u8 lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
> return sum;
> }
>
> -#ifdef CONFIG_CROS_EC_LPC_MEC
>
> -u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
> +u8 cros_ec_lpc_mec_read_bytes(unsigned int offset, unsigned int length,
> + u8 *dest)
> {
> int in_range = cros_ec_lpc_mec_in_range(offset, length);
>
> @@ -50,10 +51,12 @@ u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
> cros_ec_lpc_io_bytes_mec(MEC_IO_READ,
> offset - EC_HOST_CMD_REGION0,
> length, dest) :
> - lpc_read_bytes(offset, length, dest);
> + cros_ec_lpc_read_bytes(offset, length, dest);
> +
> }
>
> -u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
> +u8 cros_ec_lpc_mec_write_bytes(unsigned int offset, unsigned int length,
> + const u8 *msg)
> {
> int in_range = cros_ec_lpc_mec_in_range(offset, length);
>
> @@ -63,8 +66,8 @@ u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
> return in_range ?
> cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE,
> offset - EC_HOST_CMD_REGION0,
> - length, msg) :
> - lpc_write_bytes(offset, length, msg);
> + length, (u8 *)msg) :
> + cros_ec_lpc_write_bytes(offset, length, msg);
> }
>
> void cros_ec_lpc_reg_init(void)
> @@ -77,25 +80,3 @@ void cros_ec_lpc_reg_destroy(void)
> {
> cros_ec_lpc_mec_destroy();
> }
> -
> -#else /* CONFIG_CROS_EC_LPC_MEC */
> -
> -u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
> -{
> - return lpc_read_bytes(offset, length, dest);
> -}
> -
> -u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
> -{
> - return lpc_write_bytes(offset, length, msg);
> -}
> -
> -void cros_ec_lpc_reg_init(void)
> -{
> -}
> -
> -void cros_ec_lpc_reg_destroy(void)
> -{
> -}
> -
> -#endif /* CONFIG_CROS_EC_LPC_MEC */
> diff --git a/drivers/platform/chrome/cros_ec_lpc_reg.h b/drivers/platform/chrome/cros_ec_lpc_reg.h
> index 416fd2572182..f12115293e47 100644
> --- a/drivers/platform/chrome/cros_ec_lpc_reg.h
> +++ b/drivers/platform/chrome/cros_ec_lpc_reg.h
> @@ -8,25 +8,18 @@
> #ifndef __CROS_EC_LPC_REG_H
> #define __CROS_EC_LPC_REG_H
>
> -/**
> - * cros_ec_lpc_read_bytes - Read bytes from a given LPC-mapped address.
> - * Returns 8-bit checksum of all bytes read.
> - *
> - * @offset: Base read address
> - * @length: Number of bytes to read
> - * @dest: Destination buffer
> +/*
> + * A generic instance of the read function of struct lpc_driver_ops, used for
> + * the LPC EC.
> */
> u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest);
>
> -/**
> - * cros_ec_lpc_write_bytes - Write bytes to a given LPC-mapped address.
> - * Returns 8-bit checksum of all bytes written.
> - *
> - * @offset: Base write address
> - * @length: Number of bytes to write
> - * @msg: Write data buffer
> +/*
> + * A generic instance of the write function of struct lpc_driver_ops, used for
> + * the LPC EC.
> */
> -u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg);
> +u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length,
> + const u8 *msg);
>
> /**
> * cros_ec_lpc_reg_init
> diff --git a/drivers/platform/chrome/wilco_ec/Kconfig b/drivers/platform/chrome/wilco_ec/Kconfig
> index fd29cbfd3d5d..c63ff2508409 100644
> --- a/drivers/platform/chrome/wilco_ec/Kconfig
> +++ b/drivers/platform/chrome/wilco_ec/Kconfig
> @@ -1,7 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0-only
> config WILCO_EC
> tristate "ChromeOS Wilco Embedded Controller"
> - depends on ACPI && X86 && CROS_EC_LPC && CROS_EC_LPC_MEC
> + depends on ACPI && X86 && CROS_EC_LPC
> help
> If you say Y here, you get support for talking to the ChromeOS
> Wilco EC over an eSPI bus. This uses a simple byte-level protocol
> --
> 2.20.1
>
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