From mboxrd@z Thu Jan 1 00:00:00 1970 From: York Sun Subject: [PATCH] drivers/i2c/muxes/i2c-mux-reg: Change ioread endianness for readback Date: Wed, 2 Sep 2015 11:40:46 -0500 Message-ID: <1441212046-2976-1-git-send-email-yorksun@freescale.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org, alexander.sverdlin-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org, York Sun List-Id: linux-i2c@vger.kernel.org Reading the register (if allowed) after writing is to ensure writing is completed on a posted bus. The endianness of reading doesn't matter. Signed-off-by: York Sun --- drivers/i2c/muxes/i2c-mux-reg.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/drivers/i2c/muxes/i2c-mux-reg.c b/drivers/i2c/muxes/i2c-mux-reg.c index 86d41d36..7f2a1ae 100644 --- a/drivers/i2c/muxes/i2c-mux-reg.c +++ b/drivers/i2c/muxes/i2c-mux-reg.c @@ -31,28 +31,28 @@ static int i2c_mux_reg_set(const struct regmux *mux, unsigned int chan_id) if (!mux->data.reg) return -EINVAL; + /* + * Write to the register, followed by a read to ensure the write is + * completed on a "posted" bus, for example PCI or write buffers. + * The endianness of reading doesn't matter and the return data + * is not used. + */ switch (mux->data.reg_size) { case 4: - if (mux->data.little_endian) { + if (mux->data.little_endian) iowrite32(chan_id, mux->data.reg); - if (!mux->data.write_only) - ioread32(mux->data.reg); - } else { + else iowrite32be(chan_id, mux->data.reg); - if (!mux->data.write_only) - ioread32(mux->data.reg); - } + if (!mux->data.write_only) + ioread32(mux->data.reg); break; case 2: - if (mux->data.little_endian) { + if (mux->data.little_endian) iowrite16(chan_id, mux->data.reg); - if (!mux->data.write_only) - ioread16(mux->data.reg); - } else { + else iowrite16be(chan_id, mux->data.reg); - if (!mux->data.write_only) - ioread16be(mux->data.reg); - } + if (!mux->data.write_only) + ioread16(mux->data.reg); break; case 1: iowrite8(chan_id, mux->data.reg); -- 1.7.9.5