linux-kernel - Re: [PATCH 1/2] MMC: Add support MMCIF for SuperH

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Date:	Wed, 28 Apr 2010 13:54:52 +0900
From:	Yusuke Goda <yusuke.goda.sx@...esas.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	ben@...adent.org.uk, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org
Subject: Re: [PATCH 1/2] MMC: Add support MMCIF for SuperH

Hi Andrew

Thanks so much for your help.

Andrew Morton wrote:
> On Tue, 27 Apr 2010 19:15:02 +0900
> Yusuke Goda <yusuke.goda.sx@...esas.com> wrote:
> 
>>  MMCIF is MMC Host Interface in SuperH.
>>
>> ...
>>
>> +static void sh_mmcif_clock_control(struct sh_mmcif_host *host, unsigned int clk)
>> +{
>> +	int i;
>> +	struct sh_mmcif_plat_data *p = host->pd->dev.platform_data;
>> +
>> +	sh_mmcif_bitclr(host, MMCIF_CE_CLK_CTRL, CLK_ENABLE);
>> +	sh_mmcif_bitclr(host, MMCIF_CE_CLK_CTRL, CLK_CLEAR);
>> +
>> +	if (!clk)
>> +		return;
>> +	if (p->sup_pclk && clk == host->clk) {
>> +			sh_mmcif_bitset(host, MMCIF_CE_CLK_CTRL, CLK_SUP_PCLK);
>> +	} else {
>> +		for (i = 1; (unsigned int)host->clk / (1 << i) >= clk; i++)
>> +			;
> 
> I suspect this could be clarified.  Perhaps
> 
> 	i = ilog2(__roundup_pow_of_two(host->clk));
> 
> If that's wrong then include/linux/log2.h has various tools which can
> surely be used.  If they're not appropriate then please feel free to
> propose additions.
OK.
I correct it.

> 
>> +		sh_mmcif_bitset(host, MMCIF_CE_CLK_CTRL, (i - 1) << 16);
>> +	}
>> +	sh_mmcif_bitset(host, MMCIF_CE_CLK_CTRL, CLK_ENABLE);
>> +}
>> +
>>
>> ...
>>
>> +static int sh_mmcif_error_manage(struct sh_mmcif_host *host)
>> +{
>> +	u32 state1, state2;
>> +	int ret, timeout = 10000000;
>> +
>> +	host->sd_error = 0;
>> +	host->wait_int = 0;
>> +
>> +	state1 = sh_mmcif_readl(host, MMCIF_CE_HOST_STS1);
>> +	state2 = sh_mmcif_readl(host, MMCIF_CE_HOST_STS2);
>> +	pr_debug("%s: ERR HOST_STS1 = %08x\n", \
>> +			DRIVER_NAME, sh_mmcif_readl(host, MMCIF_CE_HOST_STS1));
>> +	pr_debug("%s: ERR HOST_STS2 = %08x\n", \
>> +			DRIVER_NAME, sh_mmcif_readl(host, MMCIF_CE_HOST_STS2));
>> +
>> +	if (state1 & STS1_CMDSEQ) {
>> +		pr_debug("%s: Forced end of command sequence\n", DRIVER_NAME);
>> +		sh_mmcif_bitset(host, MMCIF_CE_CMD_CTRL, CMD_CTRL_BREAK);
>> +		sh_mmcif_bitset(host, MMCIF_CE_CMD_CTRL, ~CMD_CTRL_BREAK);
>> +		while (1) {
>> +			timeout--;
>> +			if (timeout < 0) {
>> +				pr_err(DRIVER_NAME": Forceed end of " \
>> +					"command sequence timeout err\n");
>> +				return -EILSEQ;
>> +			}
>> +			if (!(sh_mmcif_readl(host, MMCIF_CE_HOST_STS1)
>> +								& STS1_CMDSEQ))
>> +				break;
>> +			mdelay(1);
>> +		}
>> +		sh_mmcif_sync_reset(host);
>> +		return -EILSEQ;
> 
> Good heavens, what is EILSEQ?
> 
> <googles a bit>
> 
>     "An illegal multibyte sequence was found in the input.  This
>      usually means that you have the wrong charactor encoding, for
>      instance the MicrosoftCorporation version of latin-1 (aka
>      iso_8859_1(7)) (which has it's own stuff like "smart quotes" in
>      the reserved bytes) instead of the real latin (or perhaps
>      utf8(7))."
> 
> Why on earth are driver writers using this in the kernel???  Imagine
> the confusion which ensues when this error code propagates all the way
> back to some poor user's console.  They'll be scrabbling around with
> language encodings not even suspecting that their hardware is busted.
> 
> People do this *a lot*.  They go grubbing through errno.h and grab
> something which looks vaguely appropriate.  But it's wrong.
> 
> If your hardware is busted then return -EIO and emit a printk to tell
> the operator what broke.
> 
>> +	}
>> +
>> +	if (state2 & STS2_CRC_ERR)
>> +		ret = -EILSEQ;
>> +	else if (state2 & STS2_TIMEOUT_ERR)
>> +		ret = -ETIMEDOUT;
>> +	else
>> +		ret = -EILSEQ;
>> +	return ret;
>> +}
Thank you.
I think that EIO is appropriate.

I revise it and send a patch.

Thanks,
Goda

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