Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753631AbbERK7P (ORCPT ); Mon, 18 May 2015 06:59:15 -0400 Received: from mga11.intel.com ([192.55.52.93]:63512 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932080AbbERK54 convert rfc822-to-8bit (ORCPT ); Mon, 18 May 2015 06:57:56 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,453,1427785200"; d="scan'208";a="727691602" From: Jani Nikula To: Luis Henriques , Jiri Slaby Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Torokhov , Ben Hutchings Subject: Re: [PATCH 3.12 071/142] drm/i915: cope with large i2c transfers In-Reply-To: <87a8x22lwv.fsf@intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <378e22f618cf6c4274fd7b928fd7b10ec380c6f6.1431761807.git.jslaby@suse.cz> <20150518095602.GD1719@ares> <87a8x22lwv.fsf@intel.com> User-Agent: Notmuch/0.19+112~g77230b0 (http://notmuchmail.org) Emacs/24.4.1 (x86_64-pc-linux-gnu) Date: Mon, 18 May 2015 14:00:04 +0300 Message-ID: <877fs62lsb.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6924 Lines: 209 On Mon, 18 May 2015, Jani Nikula wrote: > On Mon, 18 May 2015, Luis Henriques wrote: >> On Sat, May 16, 2015 at 09:37:11AM +0200, Jiri Slaby wrote: >>> From: Dmitry Torokhov >>> >>> 3.12-stable review patch. If anyone has any objections, please let me know. >>> >> >> Ben Hutchings (on CC) just asked about this patch being included on >> the 3.16 kernel [1]. Is this patch really useful for kernels < 3.17? >> Should it be reverted from all the other stable kernels (3.10, 3.14 >> and 3.16), or do you think it's harmless? > > The bug fixed by Dmitry's patch has been there since the introduction of > the gmbus code in v2.6.37 by > > commit f899fc64cda8569d0529452aafc0da31c042df2e > Author: Chris Wilson > Date: Tue Jul 20 15:44:45 2010 -0700 > > drm/i915: use GMBUS to manage i2c links > > It's just that nobody noticed before > > commit 9d8dc3e529a19e427fd379118acd132520935c5d > Author: Nick Dyer > Date: Wed Jul 23 12:49:04 2014 -0700 > > Input: atmel_mxt_ts - implement T44 message handling So to be clear, I think the fix is worth backporting anywhere you can easily backport. I did not check, but I think it may be possible to trigger this from userspace with the i2c interface. > > > BR, > Jani. > > >> >> [1] http://thread.gmane.org/gmane.linux.kernel.stable/136673 >> >> Cheers, >> -- >> Luís >> >>> =============== >>> >>> commit 9535c4757b881e06fae72a857485ad57c422b8d2 upstream. >>> >>> The hardware, according to the specs, is limited to 256 byte transfers, >>> and current driver has no protections in case users attempt to do larger >>> transfers. The code will just stomp over status register and mayhem >>> ensues. >>> >>> Let's split larger transfers into digestable chunks. Doing this allows >>> Atmel MXT driver on Pixel 1 function properly (it hasn't since commit >>> 9d8dc3e529a19e427fd379118acd132520935c5d "Input: atmel_mxt_ts - >>> implement T44 message handling" which tries to consume multiple >>> touchscreen/touchpad reports in a single transaction). >>> >>> Reviewed-by: Chris Wilson >>> Signed-off-by: Dmitry Torokhov >>> Signed-off-by: Jani Nikula >>> Signed-off-by: Jiri Slaby >>> --- >>> drivers/gpu/drm/i915/i915_reg.h | 1 + >>> drivers/gpu/drm/i915/intel_i2c.c | 66 ++++++++++++++++++++++++++++++++++------ >>> 2 files changed, 57 insertions(+), 10 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h >>> index 9d344da55056..4e0053e64f14 100644 >>> --- a/drivers/gpu/drm/i915/i915_reg.h >>> +++ b/drivers/gpu/drm/i915/i915_reg.h >>> @@ -1105,6 +1105,7 @@ >>> #define GMBUS_CYCLE_INDEX (2<<25) >>> #define GMBUS_CYCLE_STOP (4<<25) >>> #define GMBUS_BYTE_COUNT_SHIFT 16 >>> +#define GMBUS_BYTE_COUNT_MAX 256U >>> #define GMBUS_SLAVE_INDEX_SHIFT 8 >>> #define GMBUS_SLAVE_ADDR_SHIFT 1 >>> #define GMBUS_SLAVE_READ (1<<0) >>> diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c >>> index d1c1e0f7f262..36b720475dc0 100644 >>> --- a/drivers/gpu/drm/i915/intel_i2c.c >>> +++ b/drivers/gpu/drm/i915/intel_i2c.c >>> @@ -276,18 +276,17 @@ gmbus_wait_idle(struct drm_i915_private *dev_priv) >>> } >>> >>> static int >>> -gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, >>> - u32 gmbus1_index) >>> +gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv, >>> + unsigned short addr, u8 *buf, unsigned int len, >>> + u32 gmbus1_index) >>> { >>> int reg_offset = dev_priv->gpio_mmio_base; >>> - u16 len = msg->len; >>> - u8 *buf = msg->buf; >>> >>> I915_WRITE(GMBUS1 + reg_offset, >>> gmbus1_index | >>> GMBUS_CYCLE_WAIT | >>> (len << GMBUS_BYTE_COUNT_SHIFT) | >>> - (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) | >>> + (addr << GMBUS_SLAVE_ADDR_SHIFT) | >>> GMBUS_SLAVE_READ | GMBUS_SW_RDY); >>> while (len) { >>> int ret; >>> @@ -309,11 +308,35 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, >>> } >>> >>> static int >>> -gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >>> +gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, >>> + u32 gmbus1_index) >>> { >>> - int reg_offset = dev_priv->gpio_mmio_base; >>> - u16 len = msg->len; >>> u8 *buf = msg->buf; >>> + unsigned int rx_size = msg->len; >>> + unsigned int len; >>> + int ret; >>> + >>> + do { >>> + len = min(rx_size, GMBUS_BYTE_COUNT_MAX); >>> + >>> + ret = gmbus_xfer_read_chunk(dev_priv, msg->addr, >>> + buf, len, gmbus1_index); >>> + if (ret) >>> + return ret; >>> + >>> + rx_size -= len; >>> + buf += len; >>> + } while (rx_size != 0); >>> + >>> + return 0; >>> +} >>> + >>> +static int >>> +gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv, >>> + unsigned short addr, u8 *buf, unsigned int len) >>> +{ >>> + int reg_offset = dev_priv->gpio_mmio_base; >>> + unsigned int chunk_size = len; >>> u32 val, loop; >>> >>> val = loop = 0; >>> @@ -325,8 +348,8 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >>> I915_WRITE(GMBUS3 + reg_offset, val); >>> I915_WRITE(GMBUS1 + reg_offset, >>> GMBUS_CYCLE_WAIT | >>> - (msg->len << GMBUS_BYTE_COUNT_SHIFT) | >>> - (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) | >>> + (chunk_size << GMBUS_BYTE_COUNT_SHIFT) | >>> + (addr << GMBUS_SLAVE_ADDR_SHIFT) | >>> GMBUS_SLAVE_WRITE | GMBUS_SW_RDY); >>> while (len) { >>> int ret; >>> @@ -343,6 +366,29 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >>> if (ret) >>> return ret; >>> } >>> + >>> + return 0; >>> +} >>> + >>> +static int >>> +gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg) >>> +{ >>> + u8 *buf = msg->buf; >>> + unsigned int tx_size = msg->len; >>> + unsigned int len; >>> + int ret; >>> + >>> + do { >>> + len = min(tx_size, GMBUS_BYTE_COUNT_MAX); >>> + >>> + ret = gmbus_xfer_write_chunk(dev_priv, msg->addr, buf, len); >>> + if (ret) >>> + return ret; >>> + >>> + buf += len; >>> + tx_size -= len; >>> + } while (tx_size != 0); >>> + >>> return 0; >>> } >>> >>> -- >>> 2.3.7 >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe stable" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > Jani Nikula, Intel Open Source Technology Center -- Jani Nikula, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/