linux-kernel - Re: [PATCH 2/2] MEMSTICK: Add driver for Ricoh R5C592 Card reader.

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Date:	Wed, 04 Aug 2010 22:31:44 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Alex Dubov <oakad@...oo.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] MEMSTICK: Add driver for Ricoh R5C592 Card reader.

On Wed, 2010-08-04 at 19:48 +0300, Maxim Levitsky wrote: 
> On Wed, 2010-08-04 at 00:57 -0700, Alex Dubov wrote: 
> > I see two immediate problems with this patch:
> > 
> > 1. On cosmetic level, custom debug macros should not be employed. Device
> > core already have this functionality (dynamic debug levels and such). Please,
> > use dev_dbg and friends for print-outs.
> This allows much easier control for debug.
> Single module parameter is enough to adjust it.
> This helps me help users.
> (Eg, kernel compilation is out of question)
> 
> 
> > 
> > 2. On a structural level, I'd rather prefer host drivers to not start their
> > own threads. If you look at both current host implementations, they operate
> > in callback fashion. Apart from saving some resources, this reduces the
> > amount of problems encountered during suspend/resume and shutdown.
> This isn't possible.
> Hardware doesn't support interrupts on memstick bus changes, it only
> supports DMA done from/to internal FIFO, and DMA it only possible for
> 512 byte TPCs.
> 

Another question.

I see that current code ignores MEMSTICK_CAP_AUTO_GET_INT
Instread mspro_blk.c enables this capability for parallel mode, assuming
that hw supports it. Its true in my case, but might not be true in other
cases.
I think I should fix that, right?

Also I see that you bath TPC_READ_LONG_DATA/TPC_READ_LONG_DATA
Does that mean that every HW sector is larger that 512?
If so, you are doing copy on write, right?
I have small caching in my sm_ftl of last sector. It helps performance a
lot.

Also I want to clarify that the only kind of interrupts supported by hw
(besides usual card detection interrupt), is DMA done interrupt.
Thats why I have to use thread.
Doing polling in r592_submit_req (which runs in atomic context is just
cruel).
Besides, under moderate IO load, the IO thread doesn't sleep, thus there
is no overhead of wake/sleep.

Best regards,
Maxim Levitsky

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