linux-kernel - Re: [PATCH 3/7] mmc_spi: adjust for delayed data token response

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Message-Id: <200903111345.33154.david-b@pacbell.net>
Date:	Wed, 11 Mar 2009 12:45:32 -0800
From:	David Brownell <david-b@...bell.net>
To:	Wolfgang Mües <wolfgang.mues@...rswald.de>
Cc:	Pierre Ossman <drzeus@...eus.cx>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Matt Fleming" <matt@...sole-pimps.org>,
	"Mike Frysinger" <vapier.adi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] mmc_spi: adjust for delayed data token response

On Wednesday 11 March 2009, Wolfgang Mües wrote:
> @@ -639,8 +640,23 @@ mmc_spi_writeblock(struct mmc_spi_host *
>  	 * doesn't necessarily tell whether the write operation succeeded;
>  	 * it just says if the transmission was ok and whether *earlier*
>  	 * writes succeeded; see the standard.
> -	 */
> -	switch (SPI_MMC_RESPONSE_CODE(scratch->status[0])) {
> +	 *
> +	 * In practice, there are (even modern SDHC-)Cards which need
> +	 * some bits to send the response, so we have to cope with this

All hardware needs some bits to send binary data!!

Do you mean "which don't send byte-aligned responses,
contrary to MMC/SD/SDIO specifications"?


> +	 * situation and check the response bit-by-bit. Arggh!!!
> +	 */
> +	pattern  = scratch->status[0] << 24;
> +	pattern |= scratch->status[1] << 16;
> +	pattern |= scratch->status[2] << 8;
> +	pattern |= scratch->status[3];
> +
> +	/* left-adjust to leading 0 bit */
> +	while (pattern & 0x80000000)
> +		pattern <<= 1;
> +	/* right-adjust for pattern matching. Code is in bit 4..0 now. */
> +	pattern >>= 27;
> +
> +	switch (pattern) {
>  	case SPI_RESPONSE_ACCEPTED:
>  		status = 0;
>  		break;
> @@ -671,8 +687,8 @@ mmc_spi_writeblock(struct mmc_spi_host *
>  	/* Return when not busy.  If we didn't collect that status yet,
>  	 * we'll need some more I/O.
>  	 */
> -	for (i = 1; i < sizeof(scratch->status); i++) {
> -		if (scratch->status[i] != 0)
> +	for (i = 4; i < sizeof(scratch->status); i++) {
> +		if (scratch->status[i] & 0x01)

I think I see why you skip four bytes, since you used
them above.  But why change the "!= 0" test?


>  			return 0;
>  	}
>  	return mmc_spi_wait_unbusy(host, timeout);
> 
> ---
> regards
> 

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