From patchwork Thu Feb 20 15:55:33 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thierry Reding X-Patchwork-Id: 322242 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 224872C00BE for ; Fri, 21 Feb 2014 02:55:48 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754166AbaBTPzr (ORCPT ); Thu, 20 Feb 2014 10:55:47 -0500 Received: from mail-bk0-f48.google.com ([209.85.214.48]:36884 "EHLO mail-bk0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753632AbaBTPzq (ORCPT ); Thu, 20 Feb 2014 10:55:46 -0500 Received: by mail-bk0-f48.google.com with SMTP id 6so675534bkj.35 for ; Thu, 20 Feb 2014 07:55:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=Lud6ky+xqEhKDosWysPBRNAchY09XCgA3OwubyBwtDU=; b=WeBV1ASOEPaZpeLEQ7F9KieuEqgJenileuiBAsoqC0ALxj47S483sdQpimcW7j5XXd CVzlFX7XmWgLtUH/FszNRDI9QUp6Io2JBhqqs5muZn+sXbLz0rwzFlUWkSPvI8XyTjx1 wJFFmH8FG0MckRM8DE3Q8DwAg2e11Y+e6RROyjrj8R2mtblrYHbvYixC2Xv+da+JL4LC OO5n6VCS3o409lPipBK6ikKwY87kTQy6DpXkhYRpJcGrNUAXNSQH2SpP+0Yp8vpgG6PD qg2wnIKZvz0FDXvxVCcdmPspclwGZauy/EH5yl88e8ioSJX5Xv48YJmtcJObvPtP1C35 FrcQ== X-Received: by 10.204.173.65 with SMTP id o1mr792540bkz.87.1392911744275; Thu, 20 Feb 2014 07:55:44 -0800 (PST) Received: from localhost (port-49090.pppoe.wtnet.de. [46.59.192.91]) by mx.google.com with ESMTPSA id o11sm4048363bkg.13.2014.02.20.07.55.43 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Feb 2014 07:55:43 -0800 (PST) From: Thierry Reding To: dri-devel@lists.freedesktop.org Cc: Jani Nikula , Daniel Vetter , Alex Deucher , =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , intel-gfx@lists.freedesktop.org, linux-tegra@vger.kernel.org Subject: [PATCH v5 4/5] drm/dp: Allow registering AUX channels as I2C busses Date: Thu, 20 Feb 2014 16:55:33 +0100 Message-Id: <1392911734-6689-5-git-send-email-thierry.reding@gmail.com> X-Mailer: git-send-email 1.8.4.2 In-Reply-To: <1392911734-6689-1-git-send-email-thierry.reding@gmail.com> References: <1392911734-6689-1-git-send-email-thierry.reding@gmail.com> Sender: linux-tegra-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org From: Thierry Reding Implements an I2C-over-AUX I2C adapter on top of the generic drm_dp_aux infrastructure. It extracts the retry logic from existing drivers, which should help in porting those drivers to this new helper. Reviewed-by: Alex Deucher Reviewed-by: Jani Nikula Signed-off-by: Thierry Reding --- Changes in v5: - move comments partially to to header file - keep MOT set between I2C messages - return -EPROTO on short reads Changes in v4: - fix typo "bitrate" -> "bit rate" Changes in v3: - add back DRM_DEBUG_KMS and DRM_ERROR messages - embed i2c_adapter within struct drm_dp_aux - fix typo in comment drivers/gpu/drm/drm_dp_helper.c | 186 ++++++++++++++++++++++++++++++++++++++-- include/drm/drm_dp_helper.h | 12 +++ 2 files changed, 191 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 177ac7bd1851..35251af3b14e 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -357,13 +357,6 @@ EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate); * Transactions are described using a hardware-independent drm_dp_aux_msg * structure, which is passed into a driver's .transfer() implementation. * Both native and I2C-over-AUX transactions are supported. - * - * An AUX channel can also be used to transport I2C messages to a sink. A - * typical application of that is to access an EDID that's present in the - * sink device. The .transfer() function can also be used to execute such - * transactions. The drm_dp_aux_register_i2c_bus() function registers an - * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers - * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter. */ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, @@ -569,3 +562,182 @@ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) return 0; } EXPORT_SYMBOL(drm_dp_link_configure); + +/* + * I2C-over-AUX implementation + */ + +static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) +{ + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | + I2C_FUNC_SMBUS_READ_BLOCK_DATA | + I2C_FUNC_SMBUS_BLOCK_PROC_CALL | + I2C_FUNC_10BIT_ADDR; +} + +/* + * Transfer a single I2C-over-AUX message and handle various error conditions, + * retrying the transaction as appropriate. + */ +static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) +{ + unsigned int retry; + int err; + + /* + * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device + * is required to retry at least seven times upon receiving AUX_DEFER + * before giving up the AUX transaction. + */ + for (retry = 0; retry < 7; retry++) { + err = aux->transfer(aux, msg); + if (err < 0) { + if (err == -EBUSY) + continue; + + DRM_DEBUG_KMS("transaction failed: %d\n", err); + return err; + } + + if (err < msg->size) + return -EPROTO; + + switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) { + case DP_AUX_NATIVE_REPLY_ACK: + /* + * For I2C-over-AUX transactions this isn't enough, we + * need to check for the I2C ACK reply. + */ + break; + + case DP_AUX_NATIVE_REPLY_NACK: + DRM_DEBUG_KMS("native nack\n"); + return -EREMOTEIO; + + case DP_AUX_NATIVE_REPLY_DEFER: + DRM_DEBUG_KMS("native defer"); + /* + * We could check for I2C bit rate capabilities and if + * available adjust this interval. We could also be + * more careful with DP-to-legacy adapters where a + * long legacy cable may force very low I2C bit rates. + * + * For now just defer for long enough to hopefully be + * safe for all use-cases. + */ + usleep_range(500, 600); + continue; + + default: + DRM_ERROR("invalid native reply %#04x\n", msg->reply); + return -EREMOTEIO; + } + + switch (msg->reply & DP_AUX_I2C_REPLY_MASK) { + case DP_AUX_I2C_REPLY_ACK: + /* + * Both native ACK and I2C ACK replies received. We + * can assume the transfer was successful. + */ + return 0; + + case DP_AUX_I2C_REPLY_NACK: + DRM_DEBUG_KMS("I2C nack\n"); + return -EREMOTEIO; + + case DP_AUX_I2C_REPLY_DEFER: + DRM_DEBUG_KMS("I2C defer\n"); + usleep_range(400, 500); + continue; + + default: + DRM_ERROR("invalid I2C reply %#04x\n", msg->reply); + return -EREMOTEIO; + } + } + + DRM_ERROR("too many retries, giving up\n"); + return -EREMOTEIO; +} + +static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, + int num) +{ + struct drm_dp_aux *aux = adapter->algo_data; + unsigned int i, j; + + for (i = 0; i < num; i++) { + struct drm_dp_aux_msg msg; + int err; + + /* + * Many hardware implementations support FIFOs larger than a + * single byte, but it has been empirically determined that + * transferring data in larger chunks can actually lead to + * decreased performance. Therefore each message is simply + * transferred byte-by-byte. + */ + for (j = 0; j < msgs[i].len; j++) { + memset(&msg, 0, sizeof(msg)); + msg.address = msgs[i].addr; + + msg.request = (msgs[i].flags & I2C_M_RD) ? + DP_AUX_I2C_READ : + DP_AUX_I2C_WRITE; + + /* + * All messages except the last one are middle-of- + * transfer messages. + */ + if ((i < num - 1) || (j < msgs[i].len - 1)) + msg.request |= DP_AUX_I2C_MOT; + + msg.buffer = msgs[i].buf + j; + msg.size = 1; + + err = drm_dp_i2c_do_msg(aux, &msg); + if (err < 0) + return err; + } + } + + return num; +} + +static const struct i2c_algorithm drm_dp_i2c_algo = { + .functionality = drm_dp_i2c_functionality, + .master_xfer = drm_dp_i2c_xfer, +}; + +/** + * drm_dp_aux_register_i2c_bus() - register an I2C adapter for I2C-over-AUX + * @aux: DisplayPort AUX channel + * + * Returns 0 on success or a negative error code on failure. + */ +int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux) +{ + aux->ddc.algo = &drm_dp_i2c_algo; + aux->ddc.algo_data = aux; + aux->ddc.retries = 3; + + aux->ddc.class = I2C_CLASS_DDC; + aux->ddc.owner = THIS_MODULE; + aux->ddc.dev.parent = aux->dev; + aux->ddc.dev.of_node = aux->dev->of_node; + + strncpy(aux->ddc.name, dev_name(aux->dev), sizeof(aux->ddc.name)); + + return i2c_add_adapter(&aux->ddc); +} +EXPORT_SYMBOL(drm_dp_aux_register_i2c_bus); + +/** + * drm_dp_aux_unregister_i2c_bus() - unregister an I2C-over-AUX adapter + * @aux: DisplayPort AUX channel + */ +void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux) +{ + i2c_del_adapter(&aux->ddc); +} +EXPORT_SYMBOL(drm_dp_aux_unregister_i2c_bus); diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 17b3a8a5ff38..42947566e755 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -431,6 +431,7 @@ struct drm_dp_aux_msg { /** * struct drm_dp_aux - DisplayPort AUX channel + * @ddc: I2C adapter that can be used for I2C-over-AUX communication * @dev: pointer to struct device that is the parent for this AUX channel * @transfer: transfers a message representing a single AUX transaction * @@ -445,8 +446,16 @@ struct drm_dp_aux_msg { * propagate errors from the .transfer() function, with the exception of * the -EBUSY error, which causes a transaction to be retried. On a short, * helpers will return -EPROTO to make it simpler to check for failure. + * + * An AUX channel can also be used to transport I2C messages to a sink. A + * typical application of that is to access an EDID that's present in the + * sink device. The .transfer() function can also be used to execute such + * transactions. The drm_dp_aux_register_i2c_bus() function registers an + * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers + * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter. */ struct drm_dp_aux { + struct i2c_adapter ddc; struct device *dev; ssize_t (*transfer)(struct drm_dp_aux *aux, @@ -507,4 +516,7 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link); +int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux); +void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux); + #endif /* _DRM_DP_HELPER_H_ */