RE: [PATCH v3 1/2] mmc: API for accessing host supported maximum segment count and size

[Amitkumar Karwar <akarwar-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>]

Hi Shawn,

> From: Shawn Lin [mailto:shawn.lin-TNX95d0MmH7DzftRWevZcw@public.gmane.org]
> Sent: Wednesday, June 08, 2016 7:31 AM
> To: Amitkumar Karwar; linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: Nishant Sarmukadam; Wei-Ning Huang; linux-mmc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; Cathy
> Luo; Xinming Hu; shawn.lin-TNX95d0MmH7DzftRWevZcw@public.gmane.org
> Subject: Re: [PATCH v3 1/2] mmc: API for accessing host supported
> maximum segment count and size
> 
> Hi
> 
> On 2016-6-6 19:53, Amitkumar Karwar wrote:
> > From: Xinming Hu <huxm-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>
> >
> > sdio device drivers need be able to get the host supported max_segs
> > and max_seg_size, so that they know the buffer size to allocate while
> > utilizing the scatter/gather DMA buffer list.
> >
> > This patch provides API for this purpose.
> >
> > Signed-off-by: Xinming Hu <huxm-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>
> > Signed-off-by: Amitkumar Karwar <akarwar-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>
> > ---
> > v2: v2 was submitted with minor improvement like replacing BUG_ON()
> > with WARN_ON()
> > v3: Addressed below review comments from Ulf Hansson
> >      a) In v3, patch has been split into two separate patches.
> >      b) Patch 1/2 introduces an API to fetch max_seg_size and max_segs
> >      c) Replaced WARN_ON() with proper error code when sg_ptr->length
> is invalid
> >      d) Instead of duplicating the code in mmc_io_rw_extended(), extra
> bool parameter
> >         has been added to this function and used it in new APIs for
> SG.
> > ---
> >   drivers/mmc/core/sdio_io.c                         | 27
> ++++++++++++++++++++++
> >   .../wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c  |  6 ++---
> >   include/linux/mmc/sdio_func.h                      |  3 +++
> >   3 files changed, 33 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/mmc/core/sdio_io.c b/drivers/mmc/core/sdio_io.c
> > index 78cb4d5..a546c89 100644
> > --- a/drivers/mmc/core/sdio_io.c
> > +++ b/drivers/mmc/core/sdio_io.c
> > @@ -720,3 +720,30 @@ int sdio_set_host_pm_flags(struct sdio_func
> *func, mmc_pm_flag_t flags)
> >   	return 0;
> >   }
> >   EXPORT_SYMBOL_GPL(sdio_set_host_pm_flags);
> > +
> > +/**
> > + *	sdio_get_host_max_seg_size - get host maximum segment size
> > + *	@func: SDIO function attached to host
> > + */
> > +unsigned int sdio_get_host_max_seg_size(struct sdio_func *func) {
> > +	WARN_ON(!func);
> > +	WARN_ON(!func->card);
> > +
> > +	return func->card->host->max_seg_size; }
> > +EXPORT_SYMBOL_GPL(sdio_get_host_max_seg_size);
> > +
> > +/**
> > + *	sdio_get_host_max_seg_count - get host maximum segment count
> > + *	@func: SDIO function attached to host
> > + */
> > +unsigned short sdio_get_host_max_seg_count(struct sdio_func *func) {
> > +	WARN_ON(!func);
> > +	WARN_ON(!func->card);
> > +
> 
> I believe these two WARN_ON may be called too late because ...
> 
> drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcmsdh.c
> 
> void brcmf_sdiod_sgtable_alloc(struct brcmf_sdio_dev *sdiodev)
> 
> func = sdiodev->func[2];
> host = func->card->host;
> 
> you have unconditionally thought it should be ready.
> 

Yes. The WARN_ONs in this patch are redundant. We will remove them and submit updated version.

Below is the function call flow.

brcmf_sdio_probe() -> brcmf_sdio_probe_attach() -> brcmf_sdiod_sgtable_alloc()

Looks like is sdiodev->func[2] is ready in brcmf_sdio_probe() itself.

It contains below line.

        bus->blocksize = bus->sdiodev->func[2]->cur_blksize;

Regards,
Amitkumar
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