From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Sun, 2 Feb 2014 16:23:09 +0000 Subject: [PATCH v5 09/23] drm/i2c: tda998x: don't read write-only registers In-Reply-To: <5269e596e16dfe40253dce38ceb0dc4a617384c1.1390986083.git.moinejf@free.fr> References: <5269e596e16dfe40253dce38ceb0dc4a617384c1.1390986083.git.moinejf@free.fr> Message-ID: <20140202162309.GF26684@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, Jan 25, 2014 at 06:14:42PM +0100, Jean-Francois Moine wrote: > This patch takes care of the write-only registers of the tda998x. > > The registers SOFTRESET, TBG_CNTRL_0 and TBG_CNTRL_1 have all bits > cleared after reset, so, they may be fully re-written. > > The register MAT_CONTRL is set to > MAT_CONTRL_MAT_BP | MAT_CONTRL_MAT_SC(1) > after reset, so, it may be fully set again to this value. I said in v3 of this patch, which seems to remain unaddressed: > /* must be last register set: */ > - reg_clear(priv, REG_TBG_CNTRL_0, TBG_CNTRL_0_SYNC_ONCE); > + reg_write(priv, REG_TBG_CNTRL_0, 0); Register changes which have a potential effect shouldn't be part of a patch which is really only trying to avoid reading from write only registers. This could be a potential functional change - and it's probably one which Rob Clark should at least be made aware of. As I commented last time, when you're changing register values in an otherwise innocuous patch, you should comment about them in the patch description. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit".