Re: [PATCH] sdio: add MMC_CAP_VDD_165_195 host capability

[David Vrabel <david.vrabel@csr.com>]

Ohad Ben-Cohen wrote:
> From: Ohad Ben-Cohen <ohad@wizery.com>
> 
> To allow the usage of MMC_VDD_165_195, host capability
> MMC_CAP_VDD_165_195 is introduced. This is necessary
> because MMC_VDD_165_195 is currently reserved/undefined.

The host already reports what voltages it supports (in
mmc_host::ocr_avail) so a seperate MMC_CAP_* isn't needed.

This interpretation of the reserved bits in the OCR should only done for
certain cards where the bits actually do mean 1.8 V operation (with v2.0
signalling) is possible.

That's a fair amount of work so perhaps in the interim something like this:

--- a/drivers/mmc/core/sdio.c
+++ b/drivers/mmc/core/sdio.c
@@ -494,6 +494,9 @@ int mmc_attach_sdio(struct mmc_host *host, u32 ocr)
 		ocr &= ~0x7F;
 	}

+	if (ocr & MMC_VDD_165_195)
+		printk(KERN_WARNING "%s: warning: card claims non-standard 1.65-1.95
V support"
+
 	host->ocr = mmc_select_voltage(host, ocr);

 	/*

And revisit this if these bits either: a) gain a (different) standard
meaning; or b) some other card uses these bits in a different
non-standard way.  Neither seems likely.

David
-- 
David Vrabel, Senior Software Engineer, Drivers
CSR, Churchill House, Cambridge Business Park,  Tel: +44 (0)1223 692562
Cowley Road, Cambridge, CB4 0WZ                 http://www.csr.com/


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