linux-kernel - Re: Uninitialized rx_req/tx_req (was: Re: [PATCH v2 2/3] mmc: omap_hsmmc: Skip platform_get_resource

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Message-ID: <5231D9B4.5000308@ti.com>
Date:	Thu, 12 Sep 2013 20:41:48 +0530
From:	Balaji T K <balajitk@...com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Matt Porter <matt.porter@...aro.org>, Chris Ball <cjb@...top.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Tony Lindgren <tony@...mide.com>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Santosh Shilimkar <santosh.shilimkar@...com>
Subject: Re: Uninitialized rx_req/tx_req (was: Re: [PATCH v2 2/3] mmc: omap_hsmmc:
 Skip platform_get_resource_byname() for dt case)

On Thursday 12 September 2013 06:11 PM, Geert Uytterhoeven wrote:
> On Tue, Mar 5, 2013 at 10:13 PM, Matt Porter <mporter@...com> wrote:
>> From: Santosh Shilimkar <santosh.shilimkar@...com>
>>
>> MMC driver probe will abort for DT case because of failed
>> platform_get_resource_byname() lookup. Fix it by skipping resource
>> byname lookup for device tree build.
>>
>> Issue is hidden because hwmod popullates the IO resources which
>> helps to succeed platform_get_resource_byname() and probe.
>>
>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...com>
>> ---
>>   drivers/mmc/host/omap_hsmmc.c |   28 +++++++++++++++-------------
>>   1 file changed, 15 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
>> index e79b12d..8ae1225 100644
>> --- a/drivers/mmc/host/omap_hsmmc.c
>> +++ b/drivers/mmc/host/omap_hsmmc.c
>> @@ -1896,21 +1896,23 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
>>
>>          omap_hsmmc_conf_bus_power(host);
>>
>> -       res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "tx");
>> -       if (!res) {
>> -               dev_err(mmc_dev(host->mmc), "cannot get DMA TX channel\n");
>> -               ret = -ENXIO;
>> -               goto err_irq;
>> -       }
>> -       tx_req = res->start;
>> +       if (!pdev->dev.of_node) {
>> +               res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "tx");
>> +               if (!res) {
>> +                       dev_err(mmc_dev(host->mmc), "cannot get DMA TX channel\n");
>> +                       ret = -ENXIO;
>> +                       goto err_irq;
>> +               }
>> +               tx_req = res->start;
>>
>> -       res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "rx");
>> -       if (!res) {
>> -               dev_err(mmc_dev(host->mmc), "cannot get DMA RX channel\n");
>> -               ret = -ENXIO;
>> -               goto err_irq;
>> +               res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "rx");
>> +               if (!res) {
>> +                       dev_err(mmc_dev(host->mmc), "cannot get DMA RX channel\n");
>> +                       ret = -ENXIO;
>> +                       goto err_irq;
>> +               }
>> +               rx_req = res->start;
>>          }
>> -       rx_req = res->start;
>>
>>          dma_cap_zero(mask);
>>          dma_cap_set(DMA_SLAVE, mask);
>
> Now this is in mainline, I get (gcc 4.1.2):
>
> drivers/mmc/host/omap_hsmmc.c: In function ‘omap_hsmmc_probe’:
> drivers/mmc/host/omap_hsmmc.c:1779: warning: ‘rx_req’ may be used
> uninitialized in this function
> drivers/mmc/host/omap_hsmmc.c:1779: warning: ‘tx_req’ may be used
> uninitialized in this function
>
> Indeed, rx_req and tx_req are not initialized in the DT case.
>
> Initializing them to zero is probably not the right fix. Where are the values
> supposed to come from in the DT case?
>
Hi,

rx_req and tx_req are not used in DT case [1].
dma_request_slave_channel is used to get dma info from mmc dt node.

__dma_request_channel is fallback case for non dt boot.

Note __dma_request_channel is called if dma info is not populated in
dts files.

static inline struct dma_chan
*__dma_request_slave_channel_compat(const dma_cap_mask_t *mask,
				  dma_filter_fn fn, void *fn_param,
				  struct device *dev, char *name)
{
	struct dma_chan *chan;

	chan = dma_request_slave_channel(dev, name);
	if (chan)
		return chan;

	return __dma_request_channel(mask, fn, fn_param);
}

> Gr{oetje,eeting}s,
>
>                          Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds
>

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