linux-kernel - Re: [PATCH 4/4] usb: musb: Add support for MediaTek musb controller

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Date:   Thu, 10 Jan 2019 08:18:40 -0600
From:   Bin Liu <b-liu@...com>
To:     Min Guo <min.guo@...iatek.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Alan Stern <stern@...land.harvard.edu>,
        <chunfeng.yun@...iatek.com>, <linux-usb@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        Yonglong Wu <yonglong.wu@...iatek.com>
Subject: Re: [PATCH 4/4] usb: musb: Add support for MediaTek musb controller

Hi Min,

Please briefly summarize the controller differences in the commit log,
such as

- WIC interrupt registers;
- data toggle bit;
- no dedicated DMA interrupt line;

so that we can quickly understand the core driver is modified
accordingly to handle the differences.

On Thu, Jan 10, 2019 at 03:24:22PM +0800, Min Guo wrote:
> Hi Bin,

[snip]

> > > > > +		musb_writeb(mbase, MUSB_INTRUSB,
> > > > > +			musb_readb(mbase, MUSB_INTRUSB));
> > > > 
> > > > For this clearing register bit operation, please create platform hooks
> > > > musb_clearb() and musb_clearw() in struct musb_platform_ops instead,
> > > > then follow how musb_readb() pointer is assigned in
> > > > musb_init_controller() to use the W1C version for mtk platform.
> > > 
> > > I have tried implementing musb_readb(), musb_readw() interface with
> > > interrupt status W1C function in struct musb_platform_ops. But this
> > > interface will require a global variable to hold MAC basic address for
> > > judgment, and then special handling of the interrupt state. A global
> > > variable will make the driver work with only a single instance, so it
> > > can't work on some MTK platforms which have two instances.
> > 
> > I didn't mean to modify musb_read*(), but
> > 
> > > How about creating musb_clearb/w() as following:
> > > void (*clearb)(void __iomem *addr, unsigned offset, u8 data);
> > > void (*clearw)(void __iomem *addr, unsigned offset, u16 data);
> > 
> > this is what I was asking for, similar to what musb_readb/w() is
> > implemented.
> 
> I will prepare a patch for musb_clearb/w().

This doesn't have to be a separate patch.

> > > > > +		musb_writew(mbase, MUSB_INTRRX,
> > > > > +			musb_readw(mbase, MUSB_INTRRX));
> > > > > +		musb_writew(mbase, MUSB_INTRTX,
> > > > > +			musb_readw(mbase, MUSB_INTRTX));
> > > > > +	}

[snip]

> > > > > +	/* MediaTek controller has private toggle register */
> > > > 
> > > > only one toggle register for all endpoints? how does it handle
> > > > difference toggle values for different endpoints?
> > > 
> > > MediaTek controller has separate registers to describe TX/RX toggle.
> > 
> > Is it one register per endpoint?
> 
> MUSB_RXTOG/MUSB_TXTOG is common register, each bit reflects the toggle
> state of an endpoint. bit[0] not used,bit[1~8] corresponds to ep[1~8]
> 
> > > 
> > > > > +	if (musb->ops->quirks & MUSB_MTK_QUIRKS) {
> > > > > +		u16 toggle;
> > > > > +		u8 epnum = qh->hw_ep->epnum;
> > > > > +
> > > > > +		if (is_in)
> > > > > +			toggle = musb_readl(musb->mregs, MUSB_RXTOG);
> > 
> > this line seems telling there is just *one* register for all endpoints.
> 
> Yes, all endpoint share this register, endpoint and bit are one-to-one
> correspondence.

Okay, thanks. Sorry I missed the bit operation in the code below.

> 
> > > > 
> > > > should use musb_readw() instead? MUSB_RXTOG seems to be 16bit.
> > > 
> > > Ok
> > > 
> > > > > +		else
> > > > > +			toggle = musb_readl(musb->mregs, MUSB_TXTOG);
> > > > > +
> > > > > +		csr = toggle & (1 << epnum);

Regards,
-Bin.