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Date: Mon, 10 Jan 2011 22:08:48 -0500 From: Mike Frysinger <vapier@...too.org> To: linux-serial@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>, Alan Cox <alan@...rguk.ukuu.org.uk> Cc: uclinux-dist-devel@...ckfin.uclinux.org, linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de> Subject: Re: [PATCH] drivers: char: hvc: add Blackfin JTAG console support On Mon, Jan 10, 2011 at 21:43, Mike Frysinger wrote: > This converts the existing bfin_jtag_comm TTY driver to the HVC layer so > that the common HVC code can worry about all of the TTY/polling crap and > leave the Blackfin code to worry about the Blackfin bits. ive noticed a few downsides of converting to this ... hvc cant be built as a module. but not that big of a deal i guess. throughput seems to be a bit lower. the Blackfin JTAG hardware has basically a 4 byte fifo that is filled/consumed in a single shot. and the Blackfin can produce much faster than the host can consume. so atm, i have it send out 4 bytes, and the hvc layers take care of calling back into me at some point. if i add a busy loop to run a few hundred milliseconds (like HZ/4), it runs much nicer. but obviously doesnt give anyone else time to run. i cant schedule or anything as the write layers are called with a spin_lock_irqsave. any tips for how to speed this up a bit ? or is it a wash with hvc ? the code size also increased a bit ... old driver added up to ~1.7KiB while hvc stuff is like ~4KiB. but hvc does a nice job of keeping the Blackfin-specific piece small. so i guess it's a wash. -mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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