Re: Compile error in ARM architecture
Russell King - ARM Linux <[email protected]>
| Newsgroups | gmane.linux.ports.arm.general |
|---|---|
| Message-ID | <[email protected]> |
On Mon, Dec 14, 2009 at 02:37:46PM +0530, Bala Shanmugam wrote: > Russell King - ARM Linux wrote: >> We don't support the non-coherent DMA API on ARM yet - there seems to >> only be one user of it, and I don't think anyone actually uses this >> driver on ARM. >> >> > Bala: Thanks for the info. So can we add a dummy > function[dma_cache_sync] in arch/arm directory to avoid compilation > issue? What's the point if no one's using the singular driver on ARM? It just adds additional maintainence overhead, and in the case of dma_cache_sync, gives people another interface to abuse. >> Because of the limited nature of the calculation (which is basically >> a fast divide by multiplying and shifting the result) for udelay() we >> have a smaller upper limit. As stated in the ARM udelay: >> >> * With currently imposed limits, this means that we support a max delay >> * of 2000us. Further limits: HZ<=1000 and bogomips<=3355 >> >> We certainly can't shave off a factor of 10 since that would mean we'd >> have to refuse to run on any platform with a calculated bogomips in >> excess of 335 - and we already have platforms in excess of these. >> >> At the end of the day, large delays should not be done using udelay(). >> That's what mdelay() is for - m meaning millisecond. Therefore, the >> drivers wanting these millisecond delays should be using the proper >> interface for long delays - that being mdelay(). >> . >> >> > Bala: Thats well explained, Thanks. But these should not give a compilation error I believe. > If these delay values are architecture specific, these values should come > under arch/[arm or x86]/include directory to avoid compilation issues. > Please let me know if I miss something. As I stated, the drivers should be using mdelay() not udelay() for large millisecond delays. The fix is to change the drivers to use the right function. ------------------------------------------------------------------- List admin: http://lists.arm.linux.org.uk/mailman/listinfo/linux-arm FAQ: http://www.arm.linux.org.uk/mailinglists/faq.php Etiquette: http://www.arm.linux.org.uk/mailinglists/etiquette.php