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From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Timur Tabi <timur@kernel.org>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>,
	lkml <linux-kernel@vger.kernel.org>, Li Yang <leoyang.li@nxp.com>,
	Scott Wood <oss@buserror.net>,
	linuxppc-dev@lists.ozlabs.org,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Qiang Zhao <qiang.zhao@nxp.com>
Subject: Re: [PATCH v4 04/47] soc: fsl: qe: introduce qe_io{read,write}* wrappers
Date: Tue, 12 Nov 2019 08:14:20 +0100	[thread overview]
Message-ID: <e37d24c5-6d4f-c8bf-1c38-f3e8b8e85eeb@rasmusvillemoes.dk> (raw)
In-Reply-To: <CAOZdJXU35+G5CMrS3247mgMjQH7__MxP8wpW6yjn1_MLD-sGqw@mail.gmail.com>

On 12/11/2019 06.17, Timur Tabi wrote:
> On Fri, Nov 8, 2019 at 7:03 AM Rasmus Villemoes
> <linux@rasmusvillemoes.dk> wrote:
>>
>> The QUICC engine drivers use the powerpc-specific out_be32() etc. In
>> order to allow those drivers to build for other architectures, those
>> must be replaced by iowrite32be(). However, on powerpc, out_be32() is
>> a simple inline function while iowrite32be() is out-of-line. So in
>> order not to introduce a performance regression on powerpc when making
>> the drivers work on other architectures, introduce qe_io* helpers.
> 
> Isn't it also true that iowrite32be() assumes a little-endian platform
> and always does a byte swap?
> 

No. You're probably thinking of the implementation in lib/iomap.c where
one has

#define mmio_read32be(addr) swab32(readl(addr))
unsigned int ioread32be(void __iomem *addr)
{
        IO_COND(addr, return pio_read32be(port), return
mmio_read32be(addr));
        return 0xffffffff;
}


#define mmio_write32be(val,port) writel(swab32(val),port)
void iowrite32be(u32 val, void __iomem *addr)
{
        IO_COND(addr, pio_write32be(val,port), mmio_write32be(val, addr));
}

but that's because readl and writel by definition work on little-endian
registers. I.e., on a BE platform, the readl and writel implementation
must themselves contain a swab, so the above would end up doing two
swabs on a BE platform.

(On PPC, there's a separate definition of mmio_read32be, namely
writel_be, which in turn does a out_be32, so on PPC that doesn't
actually end up doing two swabs).

So ioread32be etc. have well-defined semantics: access a big-endian
register and return the result in native endianness.

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  reply	other threads:[~2019-11-12  7:14 UTC|newest]

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08 13:00 [PATCH v4 00/47] QUICC Engine support on ARM and ARM64 Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 01/47] soc: fsl: qe: remove space-before-tab Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 02/47] soc: fsl: qe: drop volatile qualifier of struct qe_ic::regs Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 03/47] soc: fsl: qe: rename qe_(clr/set/clrset)bit* helpers Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 04/47] soc: fsl: qe: introduce qe_io{read,write}* wrappers Rasmus Villemoes
2019-11-12  5:17   ` [PATCH v4 04/47] soc: fsl: qe: introduce qe_io{read, write}* wrappers Timur Tabi
2019-11-12  7:14     ` Rasmus Villemoes [this message]
2019-11-14  5:08       ` [PATCH v4 04/47] soc: fsl: qe: introduce qe_io{read,write}* wrappers Timur Tabi
2019-11-14  8:55         ` Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 05/47] soc: fsl: qe: avoid ppc-specific io accessors Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 06/47] soc: fsl: qe: replace spin_event_timeout by readx_poll_timeout_atomic Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 07/47] soc: fsl: qe: qe.c: guard use of pvr_version_is() with CONFIG_PPC32 Rasmus Villemoes
2019-11-15  4:50   ` Timur Tabi
2019-11-15  8:11     ` Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 08/47] soc: fsl: qe: drop unneeded #includes Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 09/47] soc: fsl: qe: drop assign-only high_active in qe_ic_init Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 10/47] soc: fsl: qe: remove pointless sysfs registration in qe_ic.c Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 11/47] soc: fsl: qe: use qe_ic_cascade_{low, high}_mpic also on 83xx Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 12/47] soc: fsl: qe: move calls of qe_ic_init out of arch/powerpc/ Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 13/47] powerpc/83xx: remove mpc83xx_ipic_and_qe_init_IRQ Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 14/47] powerpc/85xx: remove mostly pointless mpc85xx_qe_init() Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 15/47] soc: fsl: qe: move qe_ic_cascade_* functions to qe_ic.c Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 16/47] soc: fsl: qe: rename qe_ic_cascade_low_mpic -> qe_ic_cascade_low Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 17/47] soc: fsl: qe: remove unused qe_ic_set_* functions Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 18/47] soc: fsl: qe: don't use NO_IRQ in qe_ic.c Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 19/47] soc: fsl: qe: make qe_ic_get_{low,high}_irq static Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 20/47] soc: fsl: qe: simplify qe_ic_init() Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 21/47] soc: fsl: qe: merge qe_ic.h headers into qe_ic.c Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 22/47] soc: fsl: qe: qe.c: use of_property_read_* helpers Rasmus Villemoes
2019-11-08 13:00 ` [PATCH v4 23/47] soc: fsl: qe: qe_io.c: don't open-code of_parse_phandle() Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 24/47] soc: fsl: qe: qe_io.c: access device tree property using be32_to_cpu Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 25/47] soc: fsl: qe: qe_io.c: use of_property_read_u32() in par_io_init() Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 26/47] soc: fsl: move cpm.h from powerpc/include/asm to include/soc/fsl Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 27/47] soc/fsl/qe/qe.h: update include path for cpm.h Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 28/47] serial: ucc_uart: explicitly include soc/fsl/cpm.h Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 29/47] serial: ucc_uart: replace ppc-specific IO accessors Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 30/47] serial: ucc_uart: factor out soft_uart initialization Rasmus Villemoes
2019-11-14  5:14   ` Timur Tabi
2019-11-14  9:00     ` Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 31/47] serial: ucc_uart: stub out soft_uart_init for !CONFIG_PPC32 Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 32/47] serial: ucc_uart: use of_property_read_u32() in ucc_uart_probe() Rasmus Villemoes
2019-11-14 13:57   ` Timur Tabi
2019-11-15  8:01     ` Rasmus Villemoes
2019-11-15 14:35       ` Timur Tabi
2019-11-15 22:44         ` Scott Wood
2019-11-15  4:25   ` Timur Tabi
2019-11-15  7:57     ` Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 33/47] serial: ucc_uart: access __be32 field using be32_to_cpu Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 34/47] soc: fsl: qe: change return type of cpm_muram_alloc() to s32 Rasmus Villemoes
2019-11-12  8:01   ` Qiang Zhao
2019-11-12  8:17     ` Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 35/47] soc: fsl: qe: make cpm_muram_free() return void Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 36/47] soc: fsl: qe: make cpm_muram_free() ignore a negative offset Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 37/47] soc: fsl: qe: drop broken lazy call of cpm_muram_init() Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 38/47] soc: fsl: qe: refactor cpm_muram_alloc_common to prevent BUG on error path Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 39/47] soc: fsl: qe: avoid IS_ERR_VALUE in ucc_slow.c Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 40/47] soc: fsl: qe: drop use of IS_ERR_VALUE in qe_sdma_init() Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 41/47] soc: fsl: qe: drop pointless check " Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 42/47] soc: fsl: qe: avoid IS_ERR_VALUE in ucc_fast.c Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 43/47] net/wan/fsl_ucc_hdlc: avoid use of IS_ERR_VALUE() Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 44/47] net/wan/fsl_ucc_hdlc: fix reading of __be16 registers Rasmus Villemoes
2019-11-08 13:01 ` [PATCH v4 45/47] net/wan/fsl_ucc_hdlc: reject muram offsets above 64K Rasmus Villemoes
2019-11-15  4:41   ` Timur Tabi
2019-11-15  7:44     ` Rasmus Villemoes
2019-11-15 14:33       ` Timur Tabi
2019-11-08 13:01 ` [PATCH v4 46/47] net: ethernet: freescale: make UCC_GETH explicitly depend on PPC32 Rasmus Villemoes
2019-11-15  4:35   ` Timur Tabi
2019-11-15  5:44     ` Li Yang
2019-11-15  7:54       ` Rasmus Villemoes
2019-11-15 14:32         ` Timur Tabi
2019-11-15 14:31       ` Timur Tabi
2019-11-08 13:01 ` [PATCH v4 47/47] soc: fsl: qe: remove PPC32 dependency from CONFIG_QUICC_ENGINE Rasmus Villemoes
2019-11-08 23:48   ` Li Yang
2019-11-11  7:33     ` Rasmus Villemoes
2019-11-11 18:11       ` Li Yang
2019-11-13  2:48   ` Qiang Zhao
2019-11-20 19:42   ` kbuild test robot
2019-11-11 23:39 ` [PATCH v4 00/47] QUICC Engine support on ARM and ARM64 Li Yang
2019-11-12 20:45   ` Li Yang
2019-11-13  7:26     ` Rasmus Villemoes

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