RE: [PATCH V1 1/1] mmc: sdhci: fix DMA configure compatibility issue when 64bit DMA mode is used.

[Chevron Li (WH)]

Hi, Ulf,

Yes, this patch fixes a real problem.

BR,
Chevron

> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Sent: Thursday, June 8, 2023 23:53
> To: Chevron Li <chevron_li@xxxxxxx>
> Cc: adrian.hunter@xxxxxxxxx; linux-mmc@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Shirley Her(SC) <shirley.her@xxxxxxxxxxxxxx>;
> XiaoGuang Yu (WH) <xiaoguang.yu@xxxxxxxxxxxxxx>; Shaper Liu (WH)
> <shaper.liu@xxxxxxxxxxxxxx>; Justin Wang (WH)
> <justin.wang@xxxxxxxxxxxxxx>; Chevron Li (WH)
> <chevron.li@xxxxxxxxxxxxxx>
> Subject: Re: [PATCH V1 1/1] mmc: sdhci: fix DMA configure compatibility issue
> when 64bit DMA mode is used.
> 
> On Tue, 23 May 2023 at 13:12, Chevron Li <chevron_li@xxxxxxx> wrote:
> >
> > From: Chevron Li <chevron.li@xxxxxxxxxxxxxx>
> >
> > Bayhub SD host has hardware limitation:
> > 1.The upper 32bit address is inhibited to be written at SD Host Register
> >   [03E][13]=0 (32bits addressing) mode, is admitted to be written only at
> >   SD Host Register [03E][13]=1 (64bits addressing) mode.
> > 2.Because of above item#1, need to configure SD Host Register [03E][13] to
> >   1(64bits addressing mode) before set 64bit ADMA system address's higher
> >   32bits SD Host Register [05F~05C] if 64 bits addressing mode is used.
> >
> > The hardware limitation is reasonable for below reasons:
> > 1.Normal flow should set DMA working mode first, then do
> >   DMA-transfer-related configuration, such as system address.
> > 2.The hardware limitation may avoid the software to configure wrong higher
> >   32bit address at 32bits addressing mode although it is redundant.
> >
> > The change that set 32bits/64bits addressing mode before set ADMA
> address,
> >   has no side-effect to other host IPs for below reason:
> > The setting order is reasonable and standard: DMA Mode setting first and
> >   then DMA address setting. It meets all DMA setting sequence.
> >
> > Signed-off-by: Chevron Li <chevron.li@xxxxxxxxxxxxxx>
> 
> Applied for next, thanks!
> 
> Is this material for stable kernels too, as it fixes a real problem, no?
Yes, it fixes a real problem.
> 
> Kind regards
> Uffe
> 
> 
> > ---
> > Change in V1:
> > Set dma mode configure before set dma address
> > ---
> >  drivers/mmc/host/sdhci.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index
> > 3241916141d7..ff41aa56564e 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1167,6 +1167,8 @@ static void sdhci_prepare_data(struct sdhci_host
> *host, struct mmc_command *cmd)
> >                 }
> >         }
> >
> > +       sdhci_config_dma(host);
> > +
> >         if (host->flags & SDHCI_REQ_USE_DMA) {
> >                 int sg_cnt = sdhci_pre_dma_transfer(host, data,
> > COOKIE_MAPPED);
> >
> > @@ -1186,8 +1188,6 @@ static void sdhci_prepare_data(struct sdhci_host
> *host, struct mmc_command *cmd)
> >                 }
> >         }
> >
> > -       sdhci_config_dma(host);
> > -
> >         if (!(host->flags & SDHCI_REQ_USE_DMA)) {
> >                 int flags;
> >
> >
> > base-commit: cc3c44c9fda264c6d401be04e95449a57c1231c6
> > --
> > 2.25.1
> >