linux-kernel - [PATCH 05/14] MIPS: lantiq: Unselect SWAP_IO

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Message-Id: <20180924102803.30263-6-songjun.wu@linux.intel.com>
Date:   Mon, 24 Sep 2018 18:27:54 +0800
From:   Songjun Wu <songjun.wu@...ux.intel.com>
To:     yixin.zhu@...ux.intel.com, chuanhua.lei@...ux.intel.com,
        hauke.mehrtens@...el.com
Cc:     Songjun Wu <songjun.wu@...ux.intel.com>, linux-mips@...ux-mips.org,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 05/14] MIPS: lantiq: Unselect SWAP_IO_SPACE when LANTIQ is selected

SWAP_IO_SPACE macro prevents serial driver /drivers/tty/serial/lantiq.c
to use readl/writel to replace ltq_r32/w32 which are SoC or platform
specific APIs.

readl/writel are used for this serial driver to support multiple
platforms and multiple architectures. The legacy lantiq platform(Danube)
enables SWAP_IO_SPACE for supporting PCI due to some hardware bugs.

It's a little-endian bus plus PCI TX/RX swap enable impacted both data
and control path for MIPS based platforms. But it is better to let PCI
device driver to do endian swap since SWAP_IO_SPACE is a global wide macro
which potentially impacts other peripheral like USB.
ltq_r32/ltq_w32 is not impacted in other device drivers based on MIPS when
SWAP_IO_SPACE is not selected as they use non-byte swapping OS API
(__raw_read/__raw_writel).

Signed-off-by: Songjun Wu <songjun.wu@...ux.intel.com>
---

 arch/mips/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 138d60cf19bc..dcc1fd39cbf3 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -406,7 +406,6 @@ config LANTIQ
 	select SYS_SUPPORTS_VPE_LOADER
 	select SYS_HAS_EARLY_PRINTK
 	select GPIOLIB
-	select SWAP_IO_SPACE
 	select BOOT_RAW
 	select CLKDEV_LOOKUP
 	select USE_OF
-- 
2.11.0