From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: [PATCH v6 3/4] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Date: Fri, 15 Apr 2016 17:31:02 +0300 Message-ID: <20160415143102.GW4329@intel.com> References: <20160414170143.GS4329@intel.com> <1460730335-5012-1-git-send-email-cpaul@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <1460730335-5012-1-git-send-email-cpaul@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Lyude Cc: intel-gfx@lists.freedesktop.org, open list , dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org T24gRnJpLCBBcHIgMTUsIDIwMTYgYXQgMTA6MjU6MzVBTSAtMDQwMCwgTHl1ZGUgd3JvdGU6Cj4g VGhpcyBpcyBwYXJ0IG9mIGEgcGF0Y2ggc2VyaWVzIHRvIG1pZ3JhdGUgYWxsIG9mIHRoZSB3b3Jr YXJvdW5kcyBmb3IKPiBjb21tb25seSBzZWVuIGJlaGF2aW9yIGZyb20gYmFkIHNpbmtzIGluIGlu dGVsX2RwX2RwY2RfcmVhZF93YWtlKCkgdG8gZHJtJ3MKPiBEUCBoZWxwZXIuCj4gCj4gU29tZSBz aW5rcyB3aWxsIGp1c3QgcmV0dXJuIGdhcmJhZ2UgZm9yIHRoZSBmaXJzdCBhdXggdHJhbmFjdGlv biB0aGV5Cj4gcmVjZWl2ZSB3aGVuIGNvbWluZyBvdXQgb2Ygc2xlZXAgbW9kZSwgc28gd2UgbmVl ZCB0byBwZXJmb3JtIGFuIGFkZGl0aW9uYWwKPiByZWFkIGJlZm9yZSB0aGUgYWN0dWFsIHJlYWQg dG8gd29ya2Fyb3VuZCB0aGlzLgo+IAo+IAkJCSAgICBDaGFuZ2VzIHNpbmNlIHY1Cj4gLSBJZiB0 aGUgdGhyb3dhd2F5IHJlYWQgaW4gZHJtX2RwX2RwY2RfcmVhZCgpIGZhaWxzLCByZXR1cm4gdGhl IGVycm9yCj4gICBmcm9tIHRoYXQgaW5zdGVhZCBvZiBjb250aW51aW5nLiBUaGlzIGZvbGxvd3Mg dGhlIHNhbWUgbG9naWMgd2UgZG8gaW4KPiAgIGRybV9kcF9kcGNkX2FjY2VzcygpIChlLmcuIHRo ZSBlcnJvciBmcm9tIHRoZSBmaXJzdCB0cmFuc2FjdGlvbiBtYXkKPiAgIGRpZmZlciBmcm9tIHRo ZSBlcnJvcnMgdGhhdCBwcm9jZWVkaW5nIGF0dGVtcHRzIG1pZ2h0IHJldHVybikuCj4gCj4gU2ln bmVkLW9mZi1ieTogTHl1ZGUgPGNwYXVsQHJlZGhhdC5jb20+CgpSZXZpZXdlZC1ieTogVmlsbGUg U3lyasOkbMOkIDx2aWxsZS5zeXJqYWxhQGxpbnV4LmludGVsLmNvbT4KVGVzdGVkLWJ5OiBWaWxs ZSBTeXJqw6Rsw6QgPHZpbGxlLnN5cmphbGFAbGludXguaW50ZWwuY29tPgoKPiAtLS0KPiAgZHJp dmVycy9ncHUvZHJtL2RybV9kcF9oZWxwZXIuYyB8IDE5ICsrKysrKysrKysrKysrKysrKysKPiAg MSBmaWxlIGNoYW5nZWQsIDE5IGluc2VydGlvbnMoKykKPiAKPiBkaWZmIC0tZ2l0IGEvZHJpdmVy cy9ncHUvZHJtL2RybV9kcF9oZWxwZXIuYyBiL2RyaXZlcnMvZ3B1L2RybS9kcm1fZHBfaGVscGVy LmMKPiBpbmRleCA1NDBjM2U0Li5lZWFmNWE3IDEwMDY0NAo+IC0tLSBhL2RyaXZlcnMvZ3B1L2Ry bS9kcm1fZHBfaGVscGVyLmMKPiArKysgYi9kcml2ZXJzL2dwdS9kcm0vZHJtX2RwX2hlbHBlci5j Cj4gQEAgLTI0OCw2ICsyNDgsMjUgQEAgdW5sb2NrOgo+ICBzc2l6ZV90IGRybV9kcF9kcGNkX3Jl YWQoc3RydWN0IGRybV9kcF9hdXggKmF1eCwgdW5zaWduZWQgaW50IG9mZnNldCwKPiAgCQkJIHZv aWQgKmJ1ZmZlciwgc2l6ZV90IHNpemUpCj4gIHsKPiArCWludCByZXQ7Cj4gKwo+ICsJLyoKPiAr CSAqIEhQIFpSMjR3IGNvcnJ1cHRzIHRoZSBmaXJzdCBEUENEIGFjY2VzcyBhZnRlciBlbnRlcmlu ZyBwb3dlciBzYXZlCj4gKwkgKiBtb2RlLiBFZy4gb24gYSByZWFkLCB0aGUgZW50aXJlIGJ1ZmZl ciB3aWxsIGJlIGZpbGxlZCB3aXRoIHRoZSBzYW1lCj4gKwkgKiBieXRlLiBEbyBhIHRocm93IGF3 YXkgcmVhZCB0byBhdm9pZCBjb3JydXB0aW5nIGFueXRoaW5nIHdlIGNhcmUKPiArCSAqIGFib3V0 LiBBZnRlcndhcmRzIHRoaW5ncyB3aWxsIHdvcmsgY29ycmVjdGx5IHVudGlsIHRoZSBtb25pdG9y Cj4gKwkgKiBnZXRzIHdva2VuIHVwIGFuZCBzdWJzZXF1ZW50bHkgcmUtZW50ZXJzIHBvd2VyIHNh dmUgbW9kZS4KPiArCSAqCj4gKwkgKiBUaGUgdXNlciBwcmVzc2luZyBhbnkgYnV0dG9uIG9uIHRo ZSBtb25pdG9yIGlzIGVub3VnaCB0byB3YWtlIGl0Cj4gKwkgKiB1cCwgc28gdGhlcmUgaXMgbm8g cGFydGljdWxhcmx5IGdvb2QgcGxhY2UgdG8gZG8gdGhlIHdvcmthcm91bmQuCj4gKwkgKiBXZSBq dXN0IGhhdmUgdG8gZG8gaXQgYmVmb3JlIGFueSBEUENEIGFjY2VzcyBhbmQgaG9wZSB0aGF0IHRo ZQo+ICsJICogbW9uaXRvciBkb2Vzbid0IHBvd2VyIGRvd24gZXhhY3RseSBhZnRlciB0aGUgdGhy b3cgYXdheSByZWFkLgo+ICsJICovCj4gKwlyZXQgPSBkcm1fZHBfZHBjZF9hY2Nlc3MoYXV4LCBE UF9BVVhfTkFUSVZFX1JFQUQsIERQX0RQQ0RfUkVWLCBidWZmZXIsCj4gKwkJCQkgMSk7Cj4gKwlp ZiAocmV0ICE9IDEpCj4gKwkJcmV0dXJuIHJldDsKPiArCj4gIAlyZXR1cm4gZHJtX2RwX2RwY2Rf YWNjZXNzKGF1eCwgRFBfQVVYX05BVElWRV9SRUFELCBvZmZzZXQsIGJ1ZmZlciwKPiAgCQkJCSAg c2l6ZSk7Cj4gIH0KPiAtLSAKPiAyLjUuNQoKLS0gClZpbGxlIFN5cmrDpGzDpApJbnRlbCBPVEMK X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVs IG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8vbGlz dHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVsCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751285AbcDOOb0 (ORCPT ); Fri, 15 Apr 2016 10:31:26 -0400 Received: from mga14.intel.com ([192.55.52.115]:25735 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750722AbcDOObZ (ORCPT ); Fri, 15 Apr 2016 10:31:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,487,1455004800"; d="scan'208";a="945917376" Date: Fri, 15 Apr 2016 17:31:02 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Lyude Cc: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, David Airlie , open list Subject: Re: [PATCH v6 3/4] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Message-ID: <20160415143102.GW4329@intel.com> References: <20160414170143.GS4329@intel.com> <1460730335-5012-1-git-send-email-cpaul@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1460730335-5012-1-git-send-email-cpaul@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 15, 2016 at 10:25:35AM -0400, Lyude wrote: > This is part of a patch series to migrate all of the workarounds for > commonly seen behavior from bad sinks in intel_dp_dpcd_read_wake() to drm's > DP helper. > > Some sinks will just return garbage for the first aux tranaction they > receive when coming out of sleep mode, so we need to perform an additional > read before the actual read to workaround this. > > Changes since v5 > - If the throwaway read in drm_dp_dpcd_read() fails, return the error > from that instead of continuing. This follows the same logic we do in > drm_dp_dpcd_access() (e.g. the error from the first transaction may > differ from the errors that proceeding attempts might return). > > Signed-off-by: Lyude Reviewed-by: Ville Syrjälä Tested-by: Ville Syrjälä > --- > drivers/gpu/drm/drm_dp_helper.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c > index 540c3e4..eeaf5a7 100644 > --- a/drivers/gpu/drm/drm_dp_helper.c > +++ b/drivers/gpu/drm/drm_dp_helper.c > @@ -248,6 +248,25 @@ unlock: > ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, > void *buffer, size_t size) > { > + int ret; > + > + /* > + * HP ZR24w corrupts the first DPCD access after entering power save > + * mode. Eg. on a read, the entire buffer will be filled with the same > + * byte. Do a throw away read to avoid corrupting anything we care > + * about. Afterwards things will work correctly until the monitor > + * gets woken up and subsequently re-enters power save mode. > + * > + * The user pressing any button on the monitor is enough to wake it > + * up, so there is no particularly good place to do the workaround. > + * We just have to do it before any DPCD access and hope that the > + * monitor doesn't power down exactly after the throw away read. > + */ > + ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer, > + 1); > + if (ret != 1) > + return ret; > + > return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, > size); > } > -- > 2.5.5 -- Ville Syrjälä Intel OTC