From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Wed, 13 Jun 2012 14:24:34 +0200 Subject: [U-Boot] [PATCH] mx6: Avoid writing to read-only bits in imximage.cfg In-Reply-To: References: <4FD75739.90007@gmail.com> <201206131318.24535.marex@denx.de> Message-ID: <201206131424.35164.marex@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Dear Liu Hui-R64343, [...] > >> >> According to REV C manual, the register IOMUXC_IOMUXC_GPR4 has bits > >> >> 4 and 5 read-only and the value is always set as zero. > >> >> So write '0' to these bits instead of writing '1'. > >> > > >> >Jason, Fabio: What do you think? You should be the datasheet > >> >'masters' ;) > >> > >> Yes, according to the RM, > >> 5 > >> Reserved > >> This read-only field is reserved and always has the value 0. > >> 4 > >> Reserved > >> This read-only field is reserved and always has the value 0. > >> > >> So, write 1 should have no effect. > > > >I really dislike how "write 1 should have no effect" sounds. Can you > >please check with HW people? > > Since this is read-only bit, if you write 1 to it, it will have no effect. For how long do you work with hardware? Did it never occur to you that when you wrote 1 to an "reserved" bit, it either did something you didn't expect or you had to rework it later because the new CPU has that bit for something else? > Yes, to avoid the confusion, for example to do the read-back check, I agree > with not writing '1' to the read-only bit. Please, ask the hardware people about this. > >[..] > > > >Best regards, > >Marek Vasut Best regards, Marek Vasut