From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?gb2312?B?vrTI8Q==?= <micky_ching@realsil.com.cn>
Subject: Re: [PATCH 1/2] mfd: rtsx: add func to split u32 into register
Date: Fri, 28 Nov 2014 02:10:36 +0000
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To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "ulf.hansson@linaro.org" <ulf.hansson@linaro.org>, "sameo@linux.intel.com" <sameo@linux.intel.com>, "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>, "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>, "chris@printf.net" <chris@printf.net>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, =?gb2312?B?zfXsvw==?= <wei_wang@realsil.com.cn>, "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>, "rogerable@realtek.com" <rogerable@realtek.com>, "lee.jones@linaro.org" <lee.jones@linaro.org>
List-Id: linux-mmc@vger.kernel.org


On 11/27/2014 11:23 PM, Dan Carpenter wrote:
>> +static inline void rtsx_pci_write_be32(struct rtsx_pcr *pcr, u16 reg, u32 val)
>> >+{
>> >+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg,     0xFF, val >> 24);
>> >+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg + 1, 0xFF, val >> 16);
>> >+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg + 2, 0xFF, val >> 8);
>> >+	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg + 3, 0xFF, val);
> This assumes the cpu is little endian.  First convert to big endian
> using cpu_to_be32() and then write it out.
>
> 	__be32 be_val = cpu_to_be32()
>
> 	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg,     0xFF, be_val);
> 	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg + 1, 0xFF, be_val >> 8);
> 	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg + 2, 0xFF, be_val >> 16);
> 	rtsx_pci_add_cmd(pcr, WRITE_REG_CMD, reg + 3, 0xFF, be_val >> 24);
>
> (Written hurredly in my mail client.  May be wrong).
>
I think we better not use cpu_to_be32() here, leave the work to caller
may be better.

eg, in sd_ops.c the cmd.arg is constructed bit by bit, we can put the right
byte to the right register by shift, so the endian check is not need.